Micro-electro-mechanical system actuator

Abstract

A micro-electro-mechanical system (MEMS) actuator having a micro-spring structure is provided. An embodiment MEMS actuator includes a first microarm array including a plurality of first microarms spaced apart from each other in a first horizontal direction and a second microarm array including a plurality of second microarms spaced apart from each other in the first horizontal direction. The first micromechanical arm array and the second micromechanical arm array intervene in the first horizontal direction. The MEMS actuator also includes a metal connection structure connected to each of the first microarms and a vertical microspring structure disposed between the metal connection structure and one of the second microarms. The vertical microspring structure includes an upper portion connected to the metal connection structure and a lower portion connected to the top end of the second micromanipulator.

Description

Technical Field

[0001] Embodiments of the present disclosure are generally related to microelectromechanical system or nanoelectromechanical system devices, and more particularly to an array of micromechanical arms used in microelectromechanical system actuators. Background Art

[0002] Microelectromechanical systems (MEMS) are becoming increasingly popular, such as those miniaturized and integrated into integrated circuit manufacturing processes. MEMS generally consist of components sized between 1 micrometer and 100 micrometers, and the size of MEMS devices generally ranges between 20 micrometers and one millimeter. MEMS incorporates nanoelectromechanical systems (NEMS) and nanotechnology at the nanoscale.

[0003] MEMS devices include mechanical and electrical features formed by one or more semiconductor manufacturing processes. Embodiments of MEMS devices include microsensors that convert mechanical signals into electrical signals; microactuators that convert electrical signals into mechanical signals; and motion sensors commonly found in automobiles (such as airbag deployment systems) and smartphones. For many applications, MEMS devices are electrically connected to application-specific integrated circuits (ASICs) and external circuitry to form a complete MEMS system. However, if a MEMS device is damaged, for example, due to some impacts during use, it is difficult to repair or replace the damaged MEMS device, if not infeasible. Therefore, there is a need to manufacture reliable and shock-resistant MEMS devices. Summary of the Utility Model

[0004] According to some embodiments of the present disclosure, a microelectromechanical system actuator is provided, including: a first micro-arm array including a plurality of first micro-arms spaced apart from each other in a first horizontal direction and extending in a second horizontal direction; a second micro-arm array including a plurality of second micro-arms spaced apart from each other in the first horizontal direction and extending in the second horizontal direction, wherein the first micro-arm array and the second micro-arm array are interposed in the first horizontal direction; a metal connection structure extending in the first horizontal direction, wherein the metal connection structure is connected to a top end of each of the plurality of first micro-arms; and a vertical micro-spring structure disposed between the metal connection structure and one of the plurality of second micro-arms, wherein the vertical micro-spring structure includes: an upper portion connected to the metal connection structure; and a lower portion connected to a top end of the one of the plurality of second micro-arms, wherein the upper portion and the lower portion are connected at a center of the vertical micro-spring structure and form a first corner facing horizontally.

[0005] According to some embodiments of the present disclosure, a microelectromechanical system actuator is provided, including: a first micro-arm array including a plurality of first micro-arms spaced apart from each other in a first horizontal direction and extending in a second horizontal direction; a second micro-arm array including a plurality of second micro-arms spaced apart from each other in the first horizontal direction and extending in the second horizontal direction, wherein the first micro-arm array and the second micro-arm array are interposed in the first horizontal direction; a metal connection structure extending in the first horizontal direction, wherein the metal connection structure is connected to a top end of each of the plurality of first micro-arms; a vertical micro-spring structure disposed between the metal connection structure and at least one of the plurality of second micro-arms, wherein the vertical micro-spring structure includes: an upper portion connected to the metal connection structure; and a lower portion connected to a top end of the one of the plurality of second micro-arms, wherein the upper portion and the lower portion are connected at a center of the vertical micro-spring structure, and form a first corner facing horizontally; and a horizontal micro-spring structure disposed between one of the plurality of first micro-arms and one of the plurality of second micro-arms adjacent to the one of the plurality of first micro-arms, wherein the horizontal micro-spring structure further includes: a first portion connected to a sidewall of the one of the plurality of first micro-arms; and a second portion connected to a sidewall of the one of the plurality of second micro-arms; wherein the first portion and the second portion are connected at a center of the horizontal micro-spring structure, and form a second corner facing vertically.

[0006] According to some embodiments of the present disclosure, a microelectromechanical system actuator is provided, including: a plurality of first micromechanical arms and a plurality of second micromechanical arms spaced apart from each other, wherein the plurality of first micromechanical arms and the plurality of second micromechanical arms are interleaved, each of the plurality of first micromechanical arms and the plurality of second micromechanical arms extends downward from a top end to a bottom end, and one of the plurality of second micromechanical arms is disposed between two of the plurality of first micromechanical arms; a metal connection structure connected to the top end of each of the plurality of first micromechanical arms; and a vertical microspring structure disposed and internally connected to the top end of the one of the plurality of second micromechanical arms. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] When read in conjunction with the accompanying Figure 1 drawings, aspects of the present disclosure can be best understood from the following detailed description. It should be noted that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0008] Figure 1 FIG. is a schematic diagram of a cross-sectional view of an exemplary MEMS system including a micromechanical arm array and a microspring structure according to some embodiments;

[0009] Figure 2A FIG. is a schematic diagram of a cross-sectional view of a selected region shown in according to some embodiments; Figure 1 FIG. is a schematic diagram of a cross-sectional view of a selected region shown in according to some embodiments;

[0010] Figure 2B FIG. is a schematic diagram of a cross-sectional view of a selected region shown in according to some embodiments; Figure 2A FIG. is a schematic diagram of a cross-sectional view of a selected region shown in according to some embodiments;

[0011] Figure 2C FIG. is a schematic diagram of a cross-sectional view of another selected region shown in according to some embodiments; Figure 2A FIG. is a schematic diagram of a cross-sectional view of a selected region shown in according to some embodiments;

[0012] Figure 2D FIG. is a schematic diagram of an exemplary mechanism for forming the microspring structure shown in according to some embodiments; Figure 2A FIG. is a schematic diagram of a cross-sectional view taken along the dashed line A-A' shown in according to some embodiments;

[0013] Figure 3 FIG. is a schematic diagram of a cross-sectional view taken along the dashed line A-A' shown in according to some embodiments; Figure 1 FIG. is a schematic diagram of a cross-sectional view taken along the dashed line A-A' shown in according to some embodiments;

[0014] Figure 4 FIG. is a flowchart of an exemplary method for forming the MEMS system according to some embodiments;

[0015] Figures 5A to 5SSchematic diagram for explaining a MEMS system according to some embodiments and cross-sectional views of selected regions thereof at various stages of manufacturing the MEMS system;

[0016] Figure 6 Flowchart for explaining another exemplary method of forming a MEMS system according to some embodiments;

[0017] Figures 7A to 7H Schematic diagram for explaining a MEMS system according to some embodiments and cross-sectional views of selected regions thereof at various stages of manufacturing the MEMS system;

[0018] Figure 8 Schematic diagram of a cross-sectional view of a part of another exemplary MEMS system according to some embodiments;

[0019] Figure 9 Schematic perspective view for explaining an exemplary sensor-shift optical image stabilization (OIS) system including a MEMS system according to some embodiments.

[0020]

Symbol Explanation

[0021] 100, 500, 700, 800: MEMS systems

[0022] 101, 101a, 101b, 101c, 101d: MEMS actuators

[0023] 102: Top wafer

[0024] 103: Bottom wafer

[0025] 104: Passivation layer

[0026] 106, 501: Cavities

[0027] 107, 510, 534, 541: Top surfaces

[0028] 108: Bonding layer

[0029] 109, 508: Bottom surfaces

[0030] 110a: First micromechanical arm array

[0031] 110b: Second micromechanical arm array

[0032] 112, 112a, 112b: Micromechanical arms

[0033] 116: Metal connection structure

[0034] 118: Cover layer

[0035] 119: Fixed end

[0036] 121: Free end

[0037] 123: Body

[0038] 140: Multi-layer composite structure

[0039] 140a: Vertical double-layer composite structure

[0040] 140b: Horizontal double-layer composite structure

[0041] 141: Expansion layer

[0042] 142: Compression layer

[0043] 150: Micro-spring structure

[0044] 150a: Vertical micro-spring structure

[0045] 150b: Horizontal micro-spring structure

[0046] 151a, 151b: First layer

[0047] 152a, 152b: Second layer

[0048] 153a, 153b: First part, upper part

[0049] 154a, 154b: Second part, lower part

[0050] 155, 155a, 155b: Corner

[0051] 181: MEMS actuator section

[0052] 182: Hinge section

[0053] 183: Inner frame section

[0054] 184: Spring section

[0055] 185: Outer frame section

[0056] 190, 192, 194, 590: Region

[0057] 193, 195: Center line

[0058] 302a, 302b: Spinal beam

[0059] 304a, 304b: Main beam

[0060] 400, 600: Method

[0061] 402, 404, 406, 408, 410, 412, 414, 416, 418, 420, 422, 424, 426, 428, 430, 432, 434, 436, 438, 440, 602, 604, 606, 608, 610, 612, 614, 616, 618, 620, 622, 624, 626, 628, 630: Operations

[0062] 502: Groove

[0063] 503: Side Wall

[0064] 504, 702: Protrusion

[0065] 505: Second Side Wall

[0066] 506: Top Open End

[0067] 512: Side Wall

[0068] 520: First Oxide Layer

[0069] 520a, 528a: Oxide Layer

[0070] 524: First Metal Layer

[0071] 524a: Metal Residual Layer, Residual Metal Layer

[0072] 526: Silicon Layer

[0073] 526a: Silicon Residual Layer

[0074] 528: Second Oxide Layer

[0075] 532: First Polysilicon Layer

[0076] 532a, 532b: Polysilicon Portion

[0077] 536, 536a: Third Oxide Layer, Third Oxide Layer Portion

[0078] 540: Heterostructure

[0079] 544: Multilayer Structure

[0080] 546: Spacer

[0081] 546a: First Spacer, Spacer

[0082] 546b: Second Spacer, Spacer

[0083] 548: Opening, First Opening

[0084] 552: Fourth Oxide Layer

[0085] 552a: Oxide layer portion

[0086] 554a: Oxide residue layer

[0087] 555: Opening, second opening

[0088] 556: Opening

[0089] 558: Second metal layer

[0090] 558a: Metal layer portion

[0091] 704a: Oxide residue layer

[0092] 706a: Metal residue layer

[0093] 900: Sensor shift OIS system

[0094] 902: Image sensor

[0095] 904: Lens

[0096] α, θ: Angles

[0097] A - A': Dashed line

[0098] CD: Critical dimension

[0099] L: Length Detailed implementation

[0100] The following disclosure provides many different embodiments or examples for implementing different features of the provided subject matter. Specific examples of components and configurations are described below to simplify this disclosure. Of course, these are only examples and are not intended to be limiting. For example, in the following description, forming a first feature above or on a second feature may include embodiments where the first and second features are formed in direct contact, and may also include embodiments where additional features may be formed between the first and second features such that the first and second features are not in direct contact. In addition, this disclosure may repeat reference numerals and / or letters in various embodiments. This repetition is for simplicity and clarity purposes and does not itself indicate a relationship between the various embodiments and / or configurations discussed.

[0101] In addition, for ease of description, spatial relative terms such as "under", "below", "lower", "above", "upper", and the like may be used herein to describe the relationship of one element or feature illustrated in the figures to another element or feature. In addition to the directions depicted in the figures, spatial relative terms are also intended to encompass different orientations of the device during use or operation. The apparatus may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptors used herein may be interpreted accordingly.

[0102] In addition, depending on the context, either alone or in combination, the source / drain region may refer to the source or the drain. For example, a device may include a first source / drain region and a second source / drain region, among other components. The first source / drain region may be the source region, and the second source / drain region may be the drain region, and vice versa. One of ordinary skill in the art will be able to recognize many variations, modifications, and changes.

[0103] Some embodiments of the present disclosure are described. Additional operations may be provided before, during, and / or after the stages described in these embodiments. For different embodiments, some of the described stages may be replaced or eliminated. For different embodiments, some of the features described below may be replaced or eliminated, and additional features may be added. Although some embodiments are discussed with the operations being performed in a specific order, these operations may be performed in another logical order.

[0104] Overview.

[0105] Optical image stabilization (OIS) is a series of techniques for reducing blurring associated with the movement of a camera or other imaging device during exposure. Image stabilization is generally used in high-end image-stabilized binoculars, still photography cameras and video cameras, astronomical telescopes, and high-end smartphones. Lens-based OIS works by moving the lens to compensate for changes in the optical path. On the other hand, sensor-shift OIS works by moving the image sensor rather than the lens to compensate for changes in the optical path.

[0106] The advantage of moving the image sensor rather than the lens is that image stabilization can be achieved even on lenses manufactured without stabilization. This allows stabilization to work with many other non-stabilized lenses. This also reduces the weight and complexity of the lens. Additionally, when sensor-shift OIS technology improves, only the camera needs to be replaced to take advantage of these improvements, which is generally much cheaper than replacing all existing lenses in the case of lens-based image stabilization.

[0107] In some embodiments, sensor-shift OIS is based on a MEMS actuator that can move in, for example, five axes (i.e., X, Y, roll, pitch, and yaw). An image sensor is attached to the MEMS actuator and can thus move in five axes accordingly. In some embodiments, the MEMS actuator includes at least one array of micro-mechanical arms. Each array of micro-mechanical arms includes a plurality of micro-mechanical arms. Each micro-mechanical arm is generally an elongated structure fabricated using semiconductor processes.

[0108] However, an impact on the MEMS actuator can damage the micro-mechanical arms inside the MEMS actuator. For example, a smartphone with a MEMS actuator accidentally drops to the ground, and the impact can cause the touch screen to break and the micro-mechanical arms in the MEMS actuator inside the smartphone to be damaged. Although it is feasible to replace the touch screen, it is impractical to replace the damaged micro-mechanical arms, given that the critical dimensions of the damaged micro-mechanical arms are on the micron scale or even the nanoscale. Thus, the function of sensor-shift OIS can be severely impaired. Therefore, the robustness and shock resistance of the micro-mechanical arms are desirable. In addition, a MEMS actuator with high sensitivity and conductivity is needed.

[0109] The present disclosure provides techniques for solving the challenges mentioned above. According to some aspects of the present disclosure, a novel MEMS actuator is provided. In some embodiments, the MEMS actuator includes a first array of micro-mechanical arms and a second array of micro-mechanical arms. The first array of micro-mechanical arms includes a plurality of first micro-mechanical arms spaced apart from each other, and the second array of micro-mechanical arms includes a plurality of second micro-mechanical arms spaced apart from each other. The first array of micro-mechanical arms and the second array of micro-mechanical arms are interleaved such that each second micro-mechanical arm is located between two adjacent first micro-mechanical arms. The MEMS actuator further includes a metal connection structure connected to each of the first micro-mechanical arms. The MEMS actuator also includes at least one micro-spring structure for resisting the vibration of the micro-mechanical arms under external or environmental forces.

[0110] According to some embodiments, the MEMS actuator can include at least one vertical micro-spring structure disposed between the metal connection structure and one of the second micro-mechanical arms and interconnecting the metal connection structure and the second micro-mechanical arm in the vertical direction. According to some embodiments, the MEMS actuator can include at least one horizontal micro-spring structure disposed between the sidewalls of the first micro-mechanical arm and the second micro-mechanical arm adjacent to the first micro-mechanical arm and interconnecting them in the horizontal direction. According to some embodiments, the MEMS actuator can include at least one vertical micro-spring structure and at least one horizontal micro-spring structure.

[0111] The micro - spring structure advantageously provides vibration isolation, resonance control, and damping and energy dissipation for the MEMS actuator. The vertical micro - spring structure provides vibration resistance / isolation between the micro - robotic arm and the metal connection structure. Similarly, the horizontal micro - spring structure provides vibration resistance / isolation between adjacent micro - robotic arms. When external vibration or interference occurs, the micro - spring structure can absorb and suppress the vibration, thus preventing the vibration from being directly transmitted to the micro - robotic arm. By vibration - isolating the micro - robotic arm from the rest of the MEMS system, the micro - spring structure can reduce the impact of vibration on the movement of the micro - robotic arm during the operation of the MEMS actuator, and thus minimize unwanted oscillations. In addition, the micro - spring structure can also control resonance by changing the resonance frequency of the MEMS system and suppressing unwanted resonances, which can help reduce the amplitude of vibration and stabilize the movement of the micro - robotic arm.

[0112] In addition, the vertical micro - spring structure can add another buffer layer between the metal connection structure and the second micro - robotic arm, thus protecting the metal connection structure and the second micro - robotic arm from contact / collision under external vibration forces. Similarly, the horizontal micro - spring structure can also add another buffer layer between adjacent micro - robotic arms, thus protecting the adjacent micro - robotic arms from contact / collision.

[0113] Example MEMS system and MEMS actuator having a micro - spring structure.

[0114] Figure 1 Schematic diagram of a cross - sectional view of an exemplary MEMS system 100 including a MEMS actuator 101 according to some embodiments. Figure 2A To illustrate according to some embodiments of Figure 1 Schematic diagram of a cross - sectional view of region 190 shown in Figure 2B To illustrate according to some embodiments of Figure 2A Schematic diagram of a cross - sectional view of region 192 shown in Figure 2C To illustrate according to some embodiments of Figure 2A Schematic diagram of a cross - sectional view of region 194 shown in Figure 2D To illustrate according to some embodiments of the formation of Figure 1 and Figures 2A to 2C Schematic diagram of an exemplary mechanism of the micro - spring structure 150 shown in

[0115] In the illustrated embodiment, among other components, MEMS system 100 includes a top wafer 102 (also referred to as the "device wafer" and interchangeable with the "device wafer"), a bottom wafer 103 (also referred to as the "operating wafer" and interchangeable with the "operating wafer") bonded to the top wafer 102, a cavity 106, a passivation layer 104 disposed on the top wafer 102, and MEMS actuators 101, where the MEMS actuators 101 include a first micro - arm array 110a, a second micro - arm array 110b, a metal connection structure 116, and at least one micro - spring structure 150. Additional components may be included in the MEMS system 100.

[0116] As Figure 1 shown, the top wafer 102 (i.e., the device wafer) extends downward from the top surface 107 to the bonding layer 108 (also referred to as the bonding interface), the bottom wafer 103 extends upward from the bottom surface 109 to the bonding layer 108, and the top wafer 102 and the bottom wafer 103 are bonded via the bonding layer 108. In some embodiments, the bonding layer 108 is a fusion bonding layer. In other words, the top wafer 102 and the bottom wafer 103 are bonded via fusion bonding, for example, via a heating and / or pressing process without the need for an adhesive or an intermediate layer. In some embodiments, the top wafer 102 may have a bonding dielectric layer (not shown) at its bottom surface, and similarly, the bottom wafer 103 has a bonding dielectric layer (not shown) at its top surface, and the top wafer 102 and the bottom wafer 103 are bonded via the fusion of the bonding dielectric layers to form the bonding layer 108. The top wafer 102 and the bottom wafer 103 may each include a silicon substrate.

[0117] All or most of the cavity 106 is located between the top surface 107 of the top wafer 102 and the bottom surface 109 of the bottom wafer 103. The cavity 106 defines a continuous space to allow micro - arms or other movable micro - structures to be disposed therein and move and operate freely. In some embodiments, a portion of the cavity 106 spans the bonding layer 108 between the top wafer 102 and the bottom wafer 103.

[0118] The MEMS system 100 may have multiple sections along a horizontal direction, including a MEMS actuator section 181 (also referred to as the "drive comb section"), a hinge section 182, an internal frame section 183, a spring section 184, and an external frame section 185. The MEMS actuator section 181 includes a MEMS actuator 101 that provides controlled movement or displacement in response to an electrical signal. The hinge section 182 may include one or more hinges for enabling the pivotal movement of the MEMS actuator 101 or allowing the controlled rotation of other components within the MEMS system 100. The internal frame section 183 may provide structural support and stability to the MEMS system 100 to maintain the alignment of the various components within the MEMS system 100. The hinge section 182 may include flexible spring-like structures that provide mechanical support and elasticity to maintain the desired positioning and movement of the components within the MEMS system 100, and also provide a restoring force to return the MEMS actuator 101 to its initial position after actuation. The external frame section 185 is used to provide structural integrity to protect the internal components from external and environmental forces.

[0119] In the illustrated embodiment, the first micro-machined arm array 110a and the second micro-machined arm array 110b are located within the MEMS actuator section 181 and are substantially disposed within the top wafer 102. Among other components, the first micro-machined arm array 110a includes a plurality of micro-machined arms 112a and metal connection structures 116 connecting the micro-machined arms 112a. The micro-machined arms 112a are spaced apart from each other in a first horizontal direction (i.e., the Figure 1 X direction as shown in ). The micro-machined arms 112a are elongated and extend parallel to each other in a second horizontal direction (i.e., the Y direction). In some embodiments, each micro-machined arm 112a has a free end 121 (i.e., the bottom end) and a fixed end 119 (i.e., the top end). The fixed end 119 is connected to the metal connection structure 116. In some embodiments, the micro-machined arms 112a are suspended within a cavity 106 (i.e., there may be a gap between the top surface 107 of the top wafer 102 and the fixed end 119 of each micro-machined arm 112a). Thus, since the micro-machined arms 112a are suspended within the cavity 106, the free end 121 of each micro-machined arm 112a can move freely.

[0120] In some embodiments, each micromechanical arm 112a further includes a body 123 and a cover layer 118 disposed on the body 123 and surrounding the body 123. The cover layer 118 encapsulates the body 123 and isolates the body 123 from the cavity 106 and the metal connection structure 116. In some embodiments, the cover layer 118 can be used as an etch stop film to prevent an etchant from etching the corresponding micromechanical arm 112a during a silicon release process, which will be described below. The metal connection structure 116 extends in the X direction and connects adjacent micromechanical arms 112a. The metal connection structure 116 is attached to the fixed end 119 (i.e., the portion of the cover layer 118 at the fixed end 119 of each micromechanical arm 112a).

[0121] In some embodiments, the micromechanical arm 112a is composed of polysilicon (“polysilicon”), the cover layer 118 is composed of silicon dioxide (SiO2), and the metal connection structure 116 is composed of a metal such as aluminum copper (AlCu). It should be understood that other combinations of materials can be used in other embodiments. For example, the micromechanical arm 112a is composed of single-crystal silicon or amorphous silicon. For example, the cover layer 118 is composed of silicon nitride (Si3N4), silicon carbide (SiC), undoped silicon glass (USG), fluorosilicate glass (FSG), borophosphosilicate glass (BPSG). For example, the metal connection structure 116 can be composed of titanium nitride (TiN), tantalum nitride (TaN), an Al-Si-Cu alloy, copper (Cu), or other suitable materials.

[0122] Similarly, in addition to other components, the second micromechanical arm array 110b includes a plurality of micromechanical arms 112b. In some embodiments, the second micromechanical arm array 110b also includes a metal connection structure (such as Figure 1 the metal connection structure 116 shown in) that connects the micromechanical arms 112b, and the metal connection structure is not shown in Figure 1In the cross-section shown. The micromachined arms 112b are spaced apart from each other in the X direction. The micromachined arms 112b are elongated and extend parallel to each other in the Y direction. In some embodiments, each micromachined arm 112b extends downward from a fixed end 119 (i.e., the top end) to a free end 121 (i.e., the bottom end). The micromachined arms 112b can also be suspended in the cavity 106 in a manner similar to the micromachined arms 112a. Thus, since the micromachined arms 112b are suspended in the cavity 106, the free end 121 of each micromachined arm 112b can move freely. Similarly, each micromachined arm 112b can further include a body 123 and a cover layer 118 disposed on the body 123 and surrounding the body 123. Similarly, the cover layer 118 of the micromachined arm 112b serves as an etch stop film to prevent the etchant from etching the corresponding micromachined arm 112b during the silicon release process.

[0123] It should be understood that although two micromachined arms 112a and one micromachined arm 112 are illustrated in Figure 1 , this is not intended to be limiting. In other embodiments, the first micromachined arm array 110a can include a different number (e.g., eight) of micromachined arms 112a, and the second micromachined arm array 110b can include a different number (e.g., seven) of micromachined arms 112b. One of ordinary skill in the art will be able to recognize many changes, modifications, and variations.

[0124] The micromachined arms 112a and the micromachined arms 112b are interleaved in the X direction. In Figure 1 the embodiment shown, the micromachined arm 112b is located between two adjacent micromachined arms 112a in the X direction. A gap in the Z direction can exist between the top surface of the micromachined arm 112b and the metal connection structure 116 connected to the micromachined arm 112a.

[0125] As mentioned above, in some embodiments, the second micromachined arm array 110b includes its own metal connection structure that extends in the X direction and connects adjacent micromachined arms 112b. The metal connection structure is attached to the micromachined arm 112b, with the cover layer 118 disposed therebetween. In some embodiments, the micromachined arm 112b is composed of polysilicon, and the cover layer 118 disposed on each micromachined arm 112b is composed of an oxide. It should be understood that other combinations of materials can be employed in other embodiments.

[0126] In some embodiments, at least one micro spring structure 150 includes a vertical micro spring structure 150a disposed in a vertical direction between the metal connection structure 116 and the second micro robotic arm 112b and interconnecting them in the vertical direction. In some embodiments, at least one micro spring structure 150 includes a horizontal micro spring structure 150b disposed in a horizontal direction between the first micro robotic arm 112a and an adjacent second micro robotic arm 112b and interconnecting them in the horizontal direction. In some embodiments, at least one micro spring structure 150 includes both a vertical micro spring structure 150a and a horizontal micro spring structure 150b.

[0127] As Figure 2B shown, the vertical micro spring structure 150a has a curved configuration and includes a first layer 151a and a second layer 152a. The first layer 151a is composed of an expansion material (i.e., an expansion layer), and the second layer 152a is composed of a compression material (i.e., a compression layer). The first layer 151a and the second layer 152a are joined to each other, stacked in a horizontal direction (i.e., the X direction), and conform to each other in shape. The vertical micro spring structure 150a has a first portion 153a (i.e., an upper portion) and a second portion 154a (i.e., a lower portion). The upper portion 153a and the lower portion 154a are joined at the center of the vertical micro spring structure 150a (i.e., along the center line 193) to form a corner 155a. The corner 155a is oriented and positioned to face horizontally (i.e., in the direction from the first layer 151a (i.e., the expansion layer) to the second layer 152a (i.e., the compression layer)). The corner 155a has an angle (α) that at least partially represents the curvature of the vertical micro spring structure 150a. In some embodiments, the upper portion 153a and the lower portion 154a are substantially symmetric with respect to the center line 193. The upper portion 153a is connected to the metal connection structure 116, and the lower portion 154a is connected to the cover layer 118 of the second micro robotic arm 112b. In operation, the vertical micro spring structure 150a can undergo elastic deformation and be elongated or compressed in the vertical direction.

[0128] As mentioned above, the vertical microspring structure 150a includes an expansion layer and a compression layer joined and stacked together, and thus is composed of a composite material having different or opposite tensile properties. In some embodiments, the vertical microspring structure 150a may include more than two layers having different tensile properties (i.e., multiple expansion layers and / or multiple compression layers). In some embodiments, the first layer 151a (i.e., the expansion layer) has a first coefficient of thermal expansion (CTE), and the second layer 152a (i.e., the compression layer) has a second CTE, where the first CTE is substantially higher than the second CTE. In some embodiments, the first CTE is from 10 parts per million per degree Celsius (ppm / °C) to 50 parts per million per degree Celsius (ppm / °C), or from 10 micrometers per meter per degree Celsius (μm / m / °C) to 50 micrometers per meter per degree Celsius (μm / m / °C). In some embodiments, the second CTE is from about 0.1 ppm / °C to about 1.0 ppm / °C.

[0129] In some embodiments, the first layer 151a is composed of a metal, a metal alloy, or a metal compound. Examples of materials included in the first layer include, but are not limited to, aluminum (Al), copper (Cu), tungsten (W), nickel (Ni), AlCu alloy, etc. In some embodiments, the second layer 152a is composed of silicon, silicon oxide, borosilicate glass, FeNi alloy, etc. In some embodiments, the first layer 151a is composed of AlCu alloy, and the second layer 152a is composed of silicon oxide.

[0130] In some embodiments, the upper portion 153a and the metal connection structure 116 form an angle (θ) therebetween, and similarly, the lower portion 154a and the top surface of the second micromechanical arm 112b form an angle (θ) therebetween. In some embodiments, the angle (θ) is at least 15 degrees, at least 30 degrees, at least 45 degrees, at least 60 degrees, or at least 75 degrees. In some embodiments, the angle (α) of the corner 155a is at least 15 degrees, at least 60 degrees, at least 90 degrees, at least 120 degrees, at least 150 degrees, or at least 170 degrees.

[0131] In some embodiments, the vertical microspring structure 150a has a length (L) of at least 1.6 μm (i.e., the vertical dimension in the Z direction). The length (L) is approximately the distance between the metal connection structure 116 and the top surface of the second microactuator arm 112b. In some embodiments, the vertical microspring structure 150a has a critical dimension (CD) of at least 1 μm (i.e., the horizontal dimension in the X direction). In some embodiments, the first layer 151a has a thickness of at least 100 nm, at least 200 nm, or at least 500 nm. Similarly, the second layer 152a may have a similar thickness compared to the first layer 151a, and the thickness of the second layer 152a may be at least 100 nm, at least 200 nm, or at least 500 nm.

[0132] As Figure 2C shown, the horizontal microspring structure 150b also has a bent configuration in a manner similar to the vertical microspring structure 150a. In some embodiments, the horizontal microspring structure 150b includes a first layer 151b and a second layer 152b. The first layer 151b is composed of an expansion material (i.e., an expansion layer), and the second layer 152b is composed of a compression material (i.e., a compression layer). The first layer 151b and the second layer 152b are joined to each other, stacked in the vertical direction (i.e., the Z direction), and conform to each other in shape. The horizontal microspring structure 150b has a first portion 153b (i.e., Figure 2C the left portion shown) and a second portion 154b (i.e., Figure 2C the right portion shown). The first portion 153b and the second portion 154b are joined at the center of the horizontal microspring structure 150b (i.e., along the centerline 195) to form a corner 155b. The corner 155b of the horizontal microspring structure 150b can be oriented and positioned to face vertically (i.e., in the direction from the first layer 151b (i.e., the expansion layer) to the second layer 152b (i.e., the compression layer)). Similarly, the corner 155b has an angle (α) that at least partially represents the curvature of the horizontal microspring structure 150b. The first portion 153b and the second portion 154b may be substantially symmetric with respect to the centerline 195. The first portion 153b is connected to the cover layer 118 on the sidewall of the first microactuator arm 112a, and the second portion 154b is connected to the cover layer 118 on the sidewall of the second microactuator arm 112b adjacent to the first microactuator arm 112a. In operation, the horizontal microspring structure 150b can undergo elastic deformation and be stretched or compressed in the horizontal direction to resist the vibration of the first microactuator arm 112a and the second microactuator arm 112b.

[0133] Similar to the vertical microspring structure 150a, the horizontal microspring structure 150b is also composed of a composite material having different or opposite tensile properties. In some embodiments, the horizontal microspring structure 150b may include more than two layers having different tensile properties (i.e., multiple expansion layers and / or multiple compression layers). In some embodiments, the first layer 151b (i.e., the expansion layer) has a first CTE, and the second layer 152b (i.e., the compression layer) has a second CTE, where the first CTE is substantially higher than the second CTE. In some embodiments, the first CTE is from 10 ppm / °C to 50 ppm / °C. In some embodiments, the second CTE is from about 0.1 ppm / °C to 1.0 ppm / °C.

[0134] In some embodiments, the first layer 151b is composed of a metal, a metal alloy, or a metal compound. Examples of materials included in the first layer include, but are not limited to, aluminum (Al), copper (Cu), tungsten (W), nickel (Ni), AlCu alloy, etc. In some embodiments, the second layer 152b is composed of silicon, silicon oxide, borosilicate glass, FeNi alloy, etc. In some embodiments, the first layer 151b is composed of AlCu alloy, and the second layer 152b is composed of silicon oxide. In some embodiments, the vertical microspring structure 150a and the horizontal microspring structure 150b are composed of the same materials.

[0135] In some embodiments, the first portion 153b and the first micromechanical arm 112a form an angle (θ) therebetween, and the second portion 154b and the second micromechanical arm 112b also form an angle (θ) therebetween. In some embodiments, the angle (θ) is at least 15 degrees, at least 30 degrees, at least 45 degrees, at least 60 degrees, or at least 75 degrees. In some embodiments, the angle (α) of the corner 155b is at least 15 degrees, at least 60 degrees, at least 90 degrees, at least 120 degrees, at least 150 degrees, or at least 170 degrees.

[0136] Similar to the vertical microspring structure 150a, the horizontal microspring structure 150b has a length (L) of at least 1.6 μm (i.e., the horizontal dimension in the X direction). The length (L) is approximately the distance between the adjacent first micromechanical arm 112a and the second micromechanical arm 112b. In some embodiments, the horizontal microspring structure 150b has a critical dimension (CD) of at least 1 μm (i.e., the vertical dimension in the Z direction). In some embodiments, the first layer 151b has a thickness of at least 100 nm, at least 200 nm, or at least 500 nm. Similarly, compared to the first layer 151b, the second layer 152b may have a similar thickness, and the thickness of the second layer 152b may be at least 100 nm, at least 200 nm, or at least 500 nm. In some embodiments, the vertical and horizontal microspring structures within the MEMS actuator 101 are substantially the same in size.

[0137] In some embodiments, the MEMS actuator 101 includes a plurality of vertical microspring structures 150a and a plurality of horizontal microspring structures 150b. Each of the vertical microspring structures 150a may connect the second micromechanical arm 112b and the metal connection structure 116, and each of the horizontal microspring structures 150b may connect the adjacent first micromechanical arm 112a and the second micromechanical arm 112b. In some embodiments, more than one (e.g., in a column or array form) vertical microspring structures 150a may be used to connect each of the second micromechanical arms 112b and the metal connection structure 116, and more than one (e.g., in a row or array form) horizontal microspring structures 150b may be used to connect the adjacent micromechanical arms 112a and 112b.

[0138] The micro spring structure 150 according to the present disclosure advantageously provides vibration isolation, resonance control, and damping and energy dissipation. The vertical micro spring structure 150a provides vibration resistance / vibration isolation between the micro mechanical arm 112b and the metal connection structure 116. Similarly, the horizontal micro spring structure 150b provides vibration resistance / vibration isolation between the adjacent micro mechanical arms 112a and 112b. When external vibration or disturbance occurs, the micro spring structures 150a and 150b can absorb and suppress the vibration, thereby preventing the vibration from being directly transmitted to the micro mechanical arms 112a and 112b. By vibrationally isolating the micro mechanical arms from the rest of the MEMS system 100, the micro spring structure 150 can reduce the impact of vibration on the movement of the micro mechanical arms 112a and 112b during the operation of the MEMS actuator 101, and thus minimize unwanted oscillations. In addition, the micro spring structure 150 can also control resonance by changing the resonance frequency of the MEMS system 100 and suppressing unwanted resonances, which helps to reduce the amplitude of vibration and stabilize the movement of the micro mechanical arms 112a and 112b. In addition, the vertical micro spring structure 150a can add another buffer layer between the metal connection structure 116 and the second micro mechanical arm 112b, thereby protecting the metal connection structure 116 and the second micro mechanical arm 112b from contact / collision under external vibration forces. Similarly, the horizontal micro spring structure 150b can also add another buffer layer between the adjacent micro mechanical arms 112a and 112b, thereby protecting the adjacent micro mechanical arms 112a and 112b from contact / collision.

[0139] As Figure 2D shown, the mechanism of forming the exemplary micro spring structure 150 by the multi-layer composite structure 140 is illustrated. In the illustrated embodiment, the multi-layer composite structure 140 has a bilayer structure, including an expansion layer 141 and a compression layer 142. The expansion layer 141 and the compression layer 142 extend in the vertical direction, are joined together, and are stacked in the horizontal direction (i.e., the X direction). The expansion layer 141 and the compression layer 142 have substantially different (or opposite) tensile properties. The expansion layer 141 may have a high CTE, and the compression layer 142 may have a substantially lower CTE. Although not wishing to be limited to any particular theory, it is believed that when an annealing process is performed to heat the multi-layer composite structure 140 at a high temperature (e.g., 800 °C), the middle portion of the expansion layer 141 may undergo substantial expansion under expansion stress in the X direction toward the compression layer 142, while the middle portion of the compression layer 142 may undergo compression under compression stress in the same direction toward the compression layer 142 itself. Since the expansion direction of the middle portion of the expansion layer 141 is the same as the compression direction of the middle portion of the compression layer 142 (as Figure 2DAs illustrated by the two arrows, the multi-layer composite structure 140 can be bent in the horizontal direction in the direction from the self-expanding layer 141 to the compression layer 142 to form a micro-spring structure 150, and the micro-spring structure 150 has a bending and folding configuration with a corner 155 in the middle of the micro-spring structure 150. The degree of bending (i.e., the angle (α) of the corner 155) can depend on the CTE and materials of the expanding layer 141 and the compression layer 142, the thicknesses of the expanding layer 141 and the compression layer 142, and the annealing conditions. It should be understood that Figure 2D The mechanisms and examples are for illustrative purposes only and are not intended to be limiting. In alternative embodiments, other mechanisms can also explain the formation of the micro-spring structure 150.

[0140] Figure 3 To illustrate a cross-section taken at A-A' as shown in Figure 1 The accompanying drawings. It should be understood that Figure 3 is not drawn to scale. In the embodiment shown in Figure 3 the MEMS actuator 101 includes a first micro-mechanical arm array 110a and a second micro-mechanical arm array 110b. The first micro-mechanical arm array 110a includes micro-mechanical arms 112a extending in the Y direction, a backbone beam 302a extending in the X direction, and a main beam 304a extending in the Y direction. Similarly, the second micro-mechanical arm array 110b includes micro-mechanical arms 112b extending in the Y direction, a backbone beam 302b, and a main beam 304b extending in the Y direction.

[0141] Each micro-mechanical arm 112a has a free end and a fixed end, and the fixed end is attached to the backbone beam 302a. The backbone beam 302a connects a plurality of micro-mechanical arms 112a together. Similarly, each micro-mechanical arm 112b has a free end and a fixed end, and the fixed end is attached to the backbone beam 302b. The backbone beam 302b connects a plurality of micro-mechanical arms 112b together.

[0142] As mentioned above, the micro-mechanical arms 112a and the micro-mechanical arms 112b are interposed in the X direction. When a voltage or potential tension is applied between the adjacent micro-mechanical arms 112a and 112b, the first micro-mechanical arm array 110a and the second micro-mechanical arm array 110b are attracted to each other due to electrostatic force. In one embodiment, the electrostatic force is proportional to the square of the applied voltage.

[0143] On the other hand, the restoring force that separates the first micro-mechanical arm array 110a and the second micro-mechanical arm array 110b can be used to balance the electrostatic force. In one embodiment, the restoring force is provided by a spring structure. Therefore, the relative movement in the Y direction between the first micro-mechanical arm array 110a and the second micro-mechanical arm array 110b (as Figure 3occurs as indicated by the arrow in []. One of ordinary skill in the art should understand that movement in more directions can be achieved by combining multiple MEMS actuators that can move in different directions.

[0144] In one embodiment, the main beam 304a is fixed relative to the body of the MEMS actuator 101, while the main beam 304b moves relative to the body of the MEMS actuator. In another embodiment, the main beam 304b is fixed relative to the body of the MEMS actuator 101, while the main beam 304a moves relative to the body of the MEMS actuator. In either case, an electrical signal is converted into a mechanical signal, and the movement of the MEMS actuator 101 is controlled by the electrical signal.

[0145] It should be understood that Figure 3 the structure shown in [] is simplified to illustrate the operating principle of the MEMS actuator 101 of the embodiment. The MEMS actuator 101 may include other components as needed. One of ordinary skill in the art will be able to recognize many changes, modifications, and variations.

[0146] Embodiment manufacturing process flow.

[0147] Figure 4 is a flowchart illustrating an exemplary method for manufacturing a MEMS system 500 according to some embodiments. In the embodiment shown in [] Figure 4 the method 400 includes operations 402, 404, 406, 408, 410, 412, 414, 416, 418, 420, 422, 424, 426, 428, 430, 432, 434, 436, 438, and 440. Additional operations may be performed. It should also be understood that the sequence of the various operations discussed above with reference to [] Figure 4 is provided for illustrative purposes, and thus, other embodiments may utilize different sequences. These different sequences of operations will be included within the scope of the embodiments. Figures 5A to 5S is a schematic diagram showing cross-sectional views of a MEMS system 500 and its region 590 at various stages of manufacturing the MEMS system 500 according to some embodiments.

[0148] In operation 402, a substrate structure for forming the MEMS system is provided. In the embodiment of [] Figure 5A the substrate structure 500 (i.e., the substrate structure of the MEMS system 500 to be produced) includes a top wafer 102 (i.e., the device wafer) and a bottom wafer 103 (i.e., the operating wafer) bonded at the bonding layer 108. The top wafer has a top surface 107. The bottom wafer 103 may also include one or more cavities 501 disposed therein. The cavities 501 may be isolated from each other.

[0149] In 404, the top wafer is etched to form trenches and one or more protrusions disposed therein. The trenches and protrusions will be used to form MEMS actuators and microspring structures in subsequent operations. The trenches can be formed by performing a patterning and etching process to remove the desired portions of the top wafer. The protrusions can be formed by performing a selective etching process. In Figure 5A an embodiment, trenches 502 are formed in the top wafer 102. The trenches 502 extend upward from the bottom surface 508 to the top open end 506 and are defined by a first sidewall 503 and a second sidewall 505. At least one protrusion 504 is formed within the trenches 502. Each protrusion 504 extends vertically from the bottom surface 508 to the top surface 510 and further includes sidewalls 512. The protrusion 504 can have a height less than the depth of the trench 502 such that the top surface 510 of each protrusion 504 is located between the bottom surface 508 and the top open end 506 of the trench 502. The protrusions 504 provide support for the horizontal microspring structure to be formed, and thus the height of the protrusions 504 can determine the relative position of the horizontal microspring structure to be formed in the vertical direction.

[0150] In 406, a first oxide layer is formed. The first oxide layer (i.e., a silicon oxide layer) can be formed by performing a thermal oxidation process. In some embodiments, the substrate structure is placed in a heat pipe (also known as a high-temperature furnace or oxidation furnace), and the heat pipe is purged with an inert gas such as nitrogen (N2) to create an oxygen-free ambient environment. Then the heat pipe is heated to a desired temperature (e.g., from 800 °C to 1600 °C). Once the desired temperature is reached, oxygen or an oxygen-containing gas such as dry air or pure oxygen is introduced into the tube. The oxygen reacts with the silicon surface to form a thermal silicon oxide layer via dry oxidation. The reaction continues until the desired thickness of the thermal silicon oxide layer is reached.

[0151] In Figure 5B an embodiment, a first oxide layer 520 is formed on the top surface of the top wafer 102. The first oxide layer 520 is also deposited on the bottom surface 508 and sidewalls of the trenches 502 and on the top surface 510 and sidewalls 512 of each protrusion 504 and covers the bottom surface 508 and sidewalls and the top surface 510 and sidewalls. A portion of the first oxide layer 520 on the top surface 510 of the protrusion 504 is denoted as the oxide layer 520a, and the oxide layer 520a will be used as a compression layer for the microspring structure to be formed in subsequent operations. The first oxide layer 520 can have compressive properties and a relatively low CTE in the range of 0.1 ppm / °C to 1.0 ppm / °C.

[0152] In 408, a first metal layer is formed. The first metal layer can be formed by suitable methods such as electroplating, physical vapor deposition (PVD), or sputter deposition. In some embodiments, the first metal layer is composed of an AlCu alloy. For example, a first metal layer containing AlCu can be formed by bombarding a first target substrate of Al and a second target substrate of Cu with high-energy ions, and the ejected and sputtered Al and Cu atoms from their respective target substrates are co-deposited on the substrate structure to form a metal layer containing Al and Cu. Annealing or other post-sputter treatment processes can be performed after sputter deposition. Similarly, an electroplating process can be performed to form a metal layer of Al and Cu on the substrate structure by placing the substrate structure in an electroplating bath containing Al ions and Cu ions, applying an electric current to initiate the reduction of Al ions and Cu ions, and co-depositing Al and Cu on the substrate structure. In some embodiments, a planarization process (e.g., a chemical-mechanical polishing (CMP) process) is performed on the first metal layer.

[0153] In Figures 5B to 5C In an embodiment of, a first metal layer 524 is formed and deposited on the first oxide layer 520. The first metal layer 524 fills the trenches 502 and the spaces between the sidewalls 503 / 505 and the protrusions 504, as well as the spaces between two adjacent protrusions 504.

[0154] In 410, the first metal layer is etched to form a horizontal bilayer composite structure in the trenches and on the protrusions, respectively. In some embodiments, dry etching techniques are used to etch the metal layer. Examples of dry etching techniques include but are not limited to Reactive Ion Etching (RIE), plasma etching, Ion Beam Etching (IBE), Deep Reactive Ion Etching (DRIE), Inductively Coupled Plasma (ICP) etching, etc. One or more non-liquid or gas etchants can be used in the dry etching process. Exemplary etchants for etching the second metal layer include but are not limited to chlorine (Cl2), boron trichloride (BCl3), chlorine trifluoride (ClF3), a mixture of oxygen (O2) and carbon tetrafluoride (CF4), or a combination thereof.

[0155] In Figures 5C to 5DIn an embodiment, a patterned mask can be applied on top of the first metal layer 524 to protect / cover the region of the first metal layer 524 corresponding to and aligned with each protrusion 504 and the portion of the first oxide layer 520 disposed on its sidewall 512. A first dry etching process is performed to remove the unprotected or uncovered first metal layer 524 and form a metal residue layer 524a corresponding to and vertically aligned with each protrusion 504 on the oxide layer 520a. In some embodiments, a second etching process can be performed to further control the thickness of the metal residue layer 524a and achieve a desired thickness. Accordingly, a horizontal double-layer composite structure 140b is formed on each protrusion 504, and the horizontal double-layer composite structure 140b includes the oxide layer 520a and the metal residue layer 524a disposed on the oxide layer 520a. The horizontal double-layer composite structure 140b is disposed on the top surface 510 of the corresponding protrusion 504. The horizontal double-layer composite structure 140b serves as a precursor for forming a horizontal microspring structure 150b (such as Figure 5S as shown). After the dry etching process, the first oxide layer 520 formed in operation 404 is re-exposed, and the trench 502 is re-formed.

[0156] In 412, a silicon layer is formed. The silicon layer can be formed by performing a two-step process. In some embodiments, a two-step process is performed to form the silicon layer, starting with depositing a "seed layer" using Chemical Vapor Deposition (CVD) technology, followed by growing silicon on the seed layer using thermal deposition technology. In the first step, a thin silicon seed layer is deposited on the substrate surface via a CVD process. For example, a precursor gas such as silane (SiH4) can be introduced into the reaction chamber, where the precursor gas decomposes in the presence of a catalyst or high-energy plasma to deposit a thin layer of silicon atoms on the exposed first oxide layer of the substrate structure. The seed layer can act as a nucleation point for subsequent silicon growth. In the second step, a thermal deposition technique such as thermal evaporation is performed to grow a thicker silicon layer on top of the seed layer. A high-temperature environment (e.g., 800 °C to 1600 °C) can be used to evaporate silicon atoms from the source material. Then, a thicker silicon layer is formed on the thin silicon atom layer formed in the first step. In some embodiments, a CMP process can be performed on the silicon layer. In Figure 5E the embodiment shown, a silicon layer 526 is formed on the re-exposed first oxide layer 520. The silicon layer 526 also fills the re-formed trench 502 and covers the horizontal double-layer composite structure 140b.

[0157] In 414, the silicon layer is etched to form silicon residual layers on the horizontal bilayer composite structures respectively. Similar to operation 410, a suitable dry etching technique is used to etch the metal layer to remove the desired portions of the silicon layer and form silicon residual layers on the metal residual layers of each horizontal bilayer composite structure.

[0158] In Figures 5E to 5F an embodiment, the patterned mask used in operation 410 can be reapplied to the substrate structure 500 to protect the regions of the silicon layer 526 corresponding to and vertically aligned with the protrusions 504. Then, a dry etching process is performed to remove the portions of the silicon layer 526 corresponding to the exposed regions defined by the patterned mask. Thus, silicon residual layers 526a corresponding to the protrusions 504 are formed respectively. Each silicon residual layer 526a is formed on the metal residual layer 524a of the corresponding horizontal bilayer composite structure 140b. After the dry etching, the first oxide layer 520 is re-exposed, and the trenches 502 are re-formed. Each silicon residual layer 526a extends downward from the top opening end 506 of the trench 502 to the top surface of the metal residual layer 524a. Each silicon residual layer 526a is vertically aligned with the metal residual layer 524a and the underlying protrusion 504, and their horizontal dimensions are substantially the same. Each silicon residual layer 526a may have a top surface substantially coplanar with the top surface of the first oxide layer 520. For simplicity, each protrusion 504, the corresponding horizontal bilayer composite structure 140b (i.e., the oxide layer 520a and the metal residual layer 524a), and the silicon residual layer 526a formed on the corresponding horizontal bilayer composite structure 140b form a heterostructure 540 extending from the top surface 541 to the bottom surface 508 of the trench 502. The first oxide layer 520 (i.e., the first oxide layer 520 provided on the sidewalls 512 of the protrusion 504) partially covers the heterostructure 540.

[0159] In 416, a second oxide layer is formed to cover the silicon residual layers and the metal residual layers on each protrusion. The second oxide layer can be formed in a manner similar to operation 406. In some embodiments, before forming the second oxide layer, each silicon residual layer is further etched to further remove its top portion such that the top surface of the silicon residual layer is substantially coplanar with the top surface of the top wafer.

[0160] In Figure 5GIn an embodiment, a second oxide layer 528 is formed on the re-exposed first oxide layer 520 and also covers the top surface and sidewalls of the silicon residue layer 526a corresponding to each protrusion 504. Before forming the second oxide layer 528, each silicon residue layer 526a is further etched to remove its small top portion, such that the top surface 541 of the silicon residue layer 526a is substantially coplanar with the top surface 107 of the top wafer 102. Thus, the second oxide layer 528 and the first oxide layer 520 completely cover the sidewalls and top surface of each heterostructure 540. The portion of the second oxide layer 528 directly formed on the top surface 541 of the silicon residue layer 526a is denoted as 528a.

[0161] In 418, a first polysilicon layer is formed to form the body portion of each of the to-be-generated micromechanical arms. The first polysilicon layer can be formed using a suitable technique such as thermal deposition or atomic layer deposition (ALD). For example, a silicon-containing gas such as SiH4 or SiH2Cl2 can be used as a precursor to form a polysilicon layer on a substrate structure placed in a heat pipe at a high temperature. Similarly, an ALD process can be performed to form a polysilicon layer using a silicon-containing gas precursor and deposit the polysilicon layer on the substrate structure.

[0162] In Figures 5G to 5H In an embodiment, a first polysilicon layer 532 is formed and deposited on the second oxide layer 528. The first polysilicon layer 532 also fills the trenches 502. A plurality of polysilicon portions 532a can be formed, and the plurality of polysilicon portions 532a are used as the bodies of the micromechanical arms formed in subsequent operations. For example, a portion of the first polysilicon layer 532 fills the space in the trench 502 between the sidewall 503 and the adjacent heterostructure 540, and a portion of the first polysilicon layer 532 is denoted as polysilicon portion 532a, which is subsequently used as the body 123 of the first micromechanical arm 112a (as Figure 5J shown in). A portion of the first polysilicon layer 532 fills the space in the trench 502 between two adjacent heterostructures 540, and a portion of the first polysilicon layer 532 is denoted as polysilicon portion 532b, which is subsequently used as the body 123 of the second micromechanical arm 112b (as Figure 5J shown in). Similarly, a portion of the first polysilicon layer 532 fills the space in the trench 502 between the sidewall 505 and the adjacent heterostructure 540, and a portion of the first polysilicon layer 532 is denoted as polysilicon portion 532a, which is subsequently used as the body 123 of another first micromechanical arm 112a (as Figure 5JAs shown in []. Accordingly, two heterostructures 540 are interposed among a plurality of polysilicon portions 532a / 532b / 532a. It should be understood that the number of heterostructures 540 and polysilicon portions 532a / 532b can vary. For example, more than two heterostructures 540 and more than three polysilicon portions 532a / 532b can be formed.

[0163] In 420, the first polysilicon layer is etched to form the top surface of the polysilicon portion below the top surface of the second oxide layer. In some embodiments, a two-step process is performed. First, a CMP process is performed to remove the excess material of the first polysilicon layer and expose the top surface of each polysilicon portion. Second, a patterning and etching process is performed to remove the small top portion of each polysilicon portion to form a top surface below the top surface of the silicon residue layer. In some embodiments, wet etching techniques can be used to etch away the small top portion of each main portion. As Figure 5I shown in [], after etching the first polysilicon layer, the second oxide layer 528 is re-exposed, and the top surface 534 of each polysilicon portion 532a / 532b is exposed and below the top surface 541 of the silicon residue layer 526a of the corresponding heterostructure 540.

[0164] In 422, a third oxide layer is formed. The third oxide layer is formed and deposited on the top surface of the polysilicon portion. The third oxide layer can be formed in a manner similar to that of forming the first oxide layer and the second oxide layer in operations 406 and 416, respectively. In Figure 5J an embodiment, the third oxide layer 536 is formed on the re-exposed first oxide layer 520 and also covers the top surface 534 of each polysilicon portion 532a / 532b. The portion of the third oxide layer 536 formed on the top surface 534 of each polysilicon portion 532a / 532b is denoted as 536a. As shown in region 590, the oxide completely covers each polysilicon portion 532a / 532b, and the oxide is derived from a part of the first oxide layer 520 (provided on the sidewalls 503 / 505 and the bottom surface 508 of the trench 502 and the sidewalls of the protrusion 504 and covering the sidewalls 503 / 505 and the bottom surface 508 and the sidewalls), a part of the second oxide layer 528 (provided on the sidewalls of the residual metal layer 524a and the silicon residue layer 526a and covering these sidewalls), and the third oxide layer portion 536a (provided on the top surface 534 of the polysilicon portion 532a / 532b and covering the top surface 534). These portions of the first oxide layer, the second oxide layer, and the third oxide layer covering each polysilicon portion 532a / 532b together form the covering layer 118 of each polysilicon portion 532a / 532b. Accordingly, the micro-machined arms 112a and 112b are formed. Each of the micro-machined arms 112a and 112b includes the polysilicon portions 532a / 532b and the covering layer 118 provided thereon.

[0165] In 424, a multi-layer structure having alternating polysilicon layers and oxide layers is formed. In some embodiments, before forming the multi-layer structure, a patterning and etching process is performed to expose the top surface of each silicon residue layer. The multi-layer structure can be formed by sequentially and alternately depositing polysilicon layers and oxide layers to cover the exposed top surface of each silicon residue layer. In Figure 5K the embodiment of, before forming the multi-layer structure 544, the top surface 541 of each silicon residue layer 526a (i.e., also the top surface of each heterostructure 540) is exposed. The multi-layer structure 544 is formed and deposited on the top wafer 102 to cover the top surface of each silicon residue layer 526a and the third oxide layer 536a on each polysilicon portion 532a / 532b. In some embodiments, before forming the multi-layer structure, an etching process can be performed to remove the oxide layer 528a on the top surface of the silicon residue layer 526a to expose the top surface of the silicon residue layer 526a.

[0166] In 426, the multi-layer structure is etched to form various spacers on the top surface of the silicon residue layer (or the top surface of the heterostructure), respectively. In some embodiments, a patterning and etching process is performed to remove the unwanted portions of the multi-layer structure and leave the residue of the multi-layer structure as spacers in the desired regions. Suitable etching techniques such as dry etching, plasma etching, or wet etching can be used to etch the multi-layer structure and form the spacers. A first opening is formed between two adjacent spacers, and the first opening is vertically aligned with the polysilicon portion of one of the micromechanical arms. In Figure 5L the embodiment of, various spacers 546 including a first spacer 546a and a second spacer 546b are formed as the residue of the multi-layer structure 544. The first spacer 546a is disposed on the heterostructure 540 in the vertical direction and is substantially aligned with the heterostructure 540 (close to the sidewall 503), while the second spacer 546b is disposed on the heterostructure 540 in the vertical direction and is substantially aligned with the heterostructure 540 (close to the sidewall 505). A first opening 548 is formed between the first spacer 546a and the second spacer 546b. The first opening 548 is substantially aligned with the polysilicon portion 532b of the second micromechanical arm 112b, and the third oxide layer portion 536a disposed on the polysilicon portion 532b is exposed to the opening 548.

[0167] In 428, a fourth oxide layer is formed. The fourth oxide layer is formed on the top wafer and fills the first opening between two adjacent spacers. The fourth oxide layer can be formed in a manner similar to that of forming the first oxide layer, the second oxide layer, and the third oxide layer in operations 406, 416, and 422, respectively. In Figures 5L to 5MIn an embodiment, a fourth oxide layer 552 is formed and deposited on the top wafer 102 to fill the openings between adjacent spacers 546. A portion of the fourth oxide layer 552, which is denoted as 552a, also fills the first opening 548 between the first spacer 546a and the second spacer 546b.

[0168] In 430, the fourth oxide layer is etched to form an oxide residue layer and a second opening adjacent to the oxide residue layer. In some embodiments, patterning and etching processes are performed to remove a portion of the oxide layer in the first opening filled between two adjacent spacers and leave an oxide residue layer therein. Optionally, suitable etching techniques such as dry etching or plasma etching are used in combination with a suitable etchant to etch the fourth oxide layer and form an oxide residue layer. Accordingly, a second opening adjacent to the oxide residue layer is formed. The second opening will be used to receive and accommodate a metal residue layer to be formed in subsequent operations. In Figures 5M to 5N an embodiment, the fourth oxide layer 552 is etched to remove a portion ( Figure 5L ) of the oxide layer portion 552a disposed on the first opening 548. Figure 5L Thus, the non-removed portion of the oxide layer portion 552a remains in the opening 548 ( Figure 5L ) and forms an oxide residue layer 554a. A second opening 555 corresponding to the removed portion of the oxide layer portion 552a (i.e., Figure 5N the left portion of the first opening 548) is formed and is adjacent to the oxide residue layer 554a. It should be noted that the relative positions of the second opening 555 and the oxide residue layer 554a may vary. For example, the second opening may be on the right side while the oxide residue layer 554a may be on the left side. A plurality of openings 556 may be formed above other micro-machined arms (e.g.,

[0169] the micro-machined arm 112a of Figures 5N to 5Q ). In an embodiment, a second metal layer is formed. The second metal layer may be formed in a manner similar to the first metal layer in operation 408. The second metal layer is deposited on the top wafer and also fills the openings between the spacers. Thus, a vertical double-layer composite structure is formed. In some embodiments, the second metal layer is composed of an AlCu alloy. In

[0170] In 434, the second metal layer is etched to form a metal connection structure. In some embodiments, suitable etching techniques such as dry etching, wet etching, or plasma etching are used for the patterning and etching processes to remove the unwanted portions of the second metal layer. In some embodiments, the second metal layer is composed of an AlCu alloy. In Figure 5P the embodiment of Figure 5P , the non-removed portion of the second metal layer 558 forms a metal connection structure 116 that connects to the first micro mechanical arm 112a and the vertical bilayer composite structure 140a (i.e., the metal layer portion 558a and the oxide residue layer 554a). Other metal connection structures (not shown) that connect to the second micro mechanical arm 112b are also formed in the same process.

[0171] In 436, a passivation layer is formed and deposited on the metal connection structure. The passivation layer can consist of a dielectric material that acts as a protective barrier, thereby providing insulation and preventing moisture, contaminants, and leakage current from affecting the MEMS system. In some embodiments, the passivation layer can be composed of silicon oxide (SiO2), silicon nitride (Si3N4), silicon oxynitride (SiON), aluminum oxide (Al2O3), titanium nitride (TiN), or a combination thereof. The passivation layer can be formed by using suitable deposition techniques such as CVD, low-pressure CVD (LPCVD), plasma-enhanced CVD (PECVD), PVD, PEPVD, ALD, PEALD, etc. In Figure 5Q the embodiment of Figure 5Q , a passivation layer 104 is formed and deposited on the metal connection structure 116.

[0172] In 438, a silicon release process is performed to remove the silicon and the spacers (i.e., the non-removed multilayer structure) to form a continuous cavity. The silicon release process is sometimes also referred to as a "sacrificial release process". The silicon release process is a process of forming a structure on a sacrificial layer and then removing the sacrificial layer later to leave a gap between the structure and the termination layer located below the sacrificial layer. In one embodiment, the sacrificial layer is made of silicon or polysilicon, and the termination layer is made of silicon oxide (e.g., the first oxide layer, the second oxide layer, the third oxide layer, and the fourth oxide layer). The sacrificial layer, which can be made of polysilicon, is later etched using, for example, plasma etching. For example, sulfur hexafluoride (SF6) can be used as an etchant. During plasma etching, a small portion of sulfur hexafluoride decomposes into sulfur and fluorine, and the fluoride ions chemically react with the sacrificial layer made of polysilicon. It should be understood that the above embodiments are not intended to be limiting, and other materials, etchants, and etching processes can be employed as needed.

[0173] In some embodiments, release holes are fabricated using, for example, various lithography and etching techniques. The release holes then provide access to the sacrificial layer for the etchant used in the sacrificial release process. The etchant begins to etch through the release holes and into the cavity. The size of the release holes and other parameters such as temperature determine the etching rate of the sacrificial layer and can be designed accordingly. It should be understood that the above examples are not intended to be limiting. In some embodiments, multiple release holes may be used.

[0174] In Figures 5Q to 5R the embodiment of, in the silicon release process, selected portions of the top wafer 102, selected portions of the heterostructure 540 (i.e., the protrusions 504 and the silicon residual layer 526a), and the spacers 546 are removed respectively. Accordingly, the continuous cavity 106 is formed and is also connected to Figure 5A the cavity 501 in the substrate structure of, and the first micro-machined arm array 110a and the second micro-machined arm array 110b are formed. The first micro-machined arms 112a and the second micro-machined arms 112b are disposed in the cavity 106. The horizontal double-layer composite structure 140b and the vertical double-layer composite structure 140a are also disposed in the cavity 106. The horizontal double-layer composite structure 140b is disposed between two adjacent micro-machined arms and interconnects them, while the vertical double-layer composite structure 140a is disposed between the metal connection structure 116 and the second micro-machined arm 112b and interconnects them.

[0175] In 440, an annealing process is performed to form the micro-spring structure. The annealing process can be performed in a thermal chamber at a high temperature (e.g., 800 °C to 1600 °C) to transform the horizontal double-layer composite structure 140b and the vertical double-layer composite structure 140a into the horizontal micro-spring structure 150b and the vertical micro-spring structure 150a respectively according to the embodiment mechanism described in Figure 2D .

[0176] Figure 6 FIG. is a flowchart illustrating an exemplary method for fabricating the MEMS system 700 according to some embodiments. The method 600 is an approximate variant of the method 400 and can be used to form only the vertical micro-spring structure. Each aspect of the operations included in the method 600 is similar to the operations of the method 400 and will not be repeated here unless otherwise stated.

[0177] In Figure 6 the embodiment shown, the method 600 includes operations 602, 604, 606, 608, 610, 612, 614, 616, 618, 620, 622, 624, 626, 628, and 630. Additional operations may be performed. In addition, it should be understood that the above reference Figure 6The sequences of the various operations described are provided for illustrative purposes and, accordingly, other embodiments may utilize different sequences. These different sequences of operations will be encompassed within the scope of the embodiments. Figures 7A to 7H FIG. is a schematic diagram showing cross-sectional views of regions of a MEMS system 700 at various stages of manufacturing the MEMS system 700 according to some embodiments.

[0178] In 602, a substrate structure including a top wafer and a bottom wafer is provided. In 604, the top wafer is etched to form trenches and at least one protrusion in the trenches. In 602, a first oxide layer is formed and deposited in the trenches to cover the protrusions. In Figure 7A an embodiment, trenches 502 are formed and protrusions 702 extend downward from a top opening end 506 to a bottom surface 508 of the trenches 502. The protrusions 702 are similar in size to Figure 5F the heterostructure 540 shown in, but do not have the horizontal bilayer composite structure 140b formed in the heterostructure 540. The first oxide layer 520 is deposited on the bottom surface 508, sidewalls 503 and 505 of the trenches 502, and the top surfaces and sidewalls of each protrusion 702.

[0179] In 608, a first polysilicon layer is formed to fill the trenches. In Figure 7B an embodiment, a first polysilicon layer 532 is deposited to fill the spaces between the sidewalls 503 / 505 of the trenches and the adjacent protrusions 702 and the spaces between two adjacent protrusions 702.

[0180] In 610, the first polysilicon layer is etched to form the polysilicon portions of the micro-mechanical arms to be produced. In 612, a second oxide layer is formed to completely cover the polysilicon portions to form the micro-mechanical arms. In Figure 7C an embodiment, the first polysilicon layer 532 is etched to form polysilicon portions 532a and 532b. Additional etching steps may be performed to remove the top small portions of each polysilicon portion 532a / 532b such that the top surfaces of the polysilicon portions 532a / 532b are vertically below the top surface 541 of the protrusions 702. A second oxide layer 528 is formed to cover the top surfaces of each polysilicon portion 532a / 532b such that the first oxide layer 520 and the second oxide layer 528 completely cover each polysilicon portion 532a / 532b. Accordingly, a cover layer 118 is formed and disposed on each polysilicon portion 532a / 532b, and micro-mechanical arms 112a and 112b are correspondingly formed.

[0181] In 614, a multilayer structure is formed. In Figure 7DIn an embodiment, patterning and etching processes are performed to expose the top surface 541 of each protrusion 702. Next, a multi-layer structure 544 is formed on the top surface 541 of the protrusion 702 and the top surfaces of the micro-machined arms 112a and 112b.

[0182] In 616, the multi-layer structure is etched to form spacers on the protrusions. In Figure 7E an embodiment, various spacers including a first spacer 546a and a second spacer 546b are respectively formed on the top surface of the protrusion 702. A first opening 548 is also formed between the first spacer 546a and the second spacer 546b.

[0183] In 618, a third oxide layer is formed and fills the first opening between the two spacers respectively disposed on the top surface of the protrusion. In 620, the third oxide layer is etched to form an oxide residue layer and a second opening adjacent to the oxide residue layer. In 622, a metal layer is deposited to form a metal residue layer in the second opening. A vertical double-layer composite structure is accordingly formed. In Figure 7F an embodiment, a vertical double-layer composite structure 140a including an oxide residue layer 704a and a metal residue layer 706a adjacent to the oxide residue layer 704a is formed on the second micro-machined arm 112b.

[0184] In 624, the metal layer is etched to form a metal connection structure. In 626, a passivation layer is formed on the metal connection structure. In 628, the silicon and the spacers are removed by performing a silicon release process to form a continuous cavity and a first micro-machined arm array and a second micro-machined arm array in the cavity. In Figure 7G an embodiment, a metal connection structure 116 is formed, and a passivation layer 104 is formed on the metal connection structure 116. Selected portions of the top wafer 102, the protrusion 702, and the spacers 546a and 546b are respectively removed in the silicon release process. Accordingly, a first micro-machined arm array 110a and a second micro-machined arm array 110b are formed. The vertical double-layer composite structure 140a is disposed between the metal connection structure 116 and the second micro-machined arm 112b and interconnects them.

[0185] In 630, an annealing process is performed to form a vertical micro-spring structure. In Figure 7H an embodiment, the vertical double-layer composite structure 140a is transformed into a vertical micro-spring structure 150a via the annealing process.

[0186] Figure 8Schematic diagram of a cross-sectional view showing a part of an exemplary MEMS system according to some embodiments. In the illustrated embodiment, MEMS system 800 includes a MEMS actuator that has only a horizontal microspring structure 150b between adjacent micromechanical arms 112a and 112b. A vertical microspring structure may not be included in MEMS system 100. For example, an improved method 400 may be used to fabricate MEMS system 800 having only horizontal microspring structures by skipping selected operations (such as operations 428 and 430) to bypass the formation of vertical microspring structures according to some embodiments.

[0187] Sensor-shift OIS system using an embodiment of a MEMS system

[0188] Figure 9 FIG. illustrating a sensor-shift OIS system 900 according to some embodiments. Among other components, sensor-shift OIS system 900 includes MEMS system 100 (such as Figure 1 the MEMS system shown), image sensor 902, and lens 904.

[0189] Image sensor 902 is attached to MEMS system 100 and is operable to detect and transmit information for image making. Image sensor 902 converts the variable attenuation of light waves passing through lens 904 into a signal. In one embodiment, image sensor 902 is a charge-coupled device (CCD). In another embodiment, image sensor 902 is a CMOS image sensor (CIS). A CMOS image sensor generally includes microlenses for collecting light, a color filter for separating out red, green, and blue (i.e., "RGB") components, and photodiodes for capturing the filtered light. In some embodiments, the CMOS image sensor is a front-side illumination (FSI) CMOS image sensor. In another embodiment, the CMOS image sensor is a backside illumination (BSI) CMOS image sensor.

[0190] As explained above, MEMS system 100 includes, for example, four MEMS actuators 101a, 101b, 101c, and 101d (collectively referred to as MEMS actuators 101), each of which can move in one direction and is controlled in motion by an electrical signal. Thus, image sensor 902 attached to MEMS system 100 can be moved correspondingly under the control of an electrical signal, thereby achieving sensor-shift OIS.

[0191] Summary.

[0192] According to some aspects of the present disclosure, a microelectromechanical system (MEMS) actuator is provided. In one embodiment, the MEMS actuator includes a first array of micromachined arms, the first array of micromachined arms including a plurality of first micromachined arms spaced apart from each other in a first horizontal direction and extending in a second horizontal direction. The MEMS actuator further includes a second array of micromachined arms, the second array of micromachined arms including a plurality of second micromachined arms spaced apart from each other in the first horizontal direction and extending in the second horizontal direction, wherein the first array of micromachined arms and the second array of micromachined arms are interleaved in the first horizontal direction. The MEMS actuator further includes a metal connection structure extending in the first horizontal direction and connected to the top end of each of the plurality of first micromachined arms. The MEMS actuator further includes a vertical microspring structure disposed between the metal connection structure and one of the plurality of second micromachined arms. The vertical microspring structure includes an upper portion connected to the metal connection structure and a lower portion connected to the top end of the one of the plurality of second micromachined arms. The upper portion and the lower portion are connected at the center of the vertical microspring structure and form a first corner facing horizontally.

[0193] In some embodiments, each of the plurality of first micromachined arms and the plurality of second micromachined arms further includes a body and a covering layer, the covering layer disposed on the body and surrounding the body, the body being composed of polysilicon, and the covering layer being composed of thermal oxide.

[0194] In some embodiments, the vertical microspring structure further includes a first layer and a second layer joined and stacked with each other in the first horizontal direction.

[0195] In some embodiments, the first layer is composed of an expansion material having a first coefficient of thermal expansion, the second layer is composed of a compression material having a second coefficient of thermal expansion, and the first coefficient of thermal expansion is at least 10 times higher than the second coefficient of thermal expansion.

[0196] In some embodiments, the first coefficient of thermal expansion is 10 ppm / °C to 50 ppm / °C, and the second coefficient of thermal expansion is 0.1 ppm / °C to 1.0 ppm / °C.

[0197] In some embodiments, the first layer is a metal layer composed of an aluminum-copper alloy.

[0198] In some embodiments, the second layer is an oxide layer composed of thermal silicon dioxide.

[0199] In some embodiments, the first corner has an angle of 15 degrees to 170 degrees.

[0200] In some embodiments, the upper portion forms a first angle with the metal connection structure, the lower portion also forms a second angle with the top of the plurality of second micro - mechanical arms, and the first angle and the second angle are at least 15 degrees.

[0201] In some embodiments, the vertical micro - spring structure has a critical dimension of at least 1 μm in the first horizontal direction.

[0202] In some embodiments, the vertical micro - spring structure has a vertical dimension of at least 1.6 μm.

[0203] In another embodiment, the MEMS actuator includes a first micro - mechanical arm array and a second micro - mechanical arm array. The first micro - mechanical arm array includes a plurality of first micro - mechanical arms spaced apart from each other in a first horizontal direction and extending in a second horizontal direction. The second micro - mechanical arm array includes a plurality of second micro - mechanical arms spaced apart from each other in the first horizontal direction and extending in the second horizontal direction. The first micro - mechanical arm array and the second micro - mechanical arm array are interposed in the first horizontal direction. The MEMS actuator further includes a metal connection structure extending in the first horizontal direction, and the metal connection structure is connected to the top of each of the plurality of first micro - mechanical arms. The MEMS actuator further includes a vertical micro - spring structure disposed between the metal connection structure and at least one of the plurality of second micro - mechanical arms. The vertical micro - spring structure includes an upper portion connected to the metal connection structure and a lower portion connected to the top of the second micro - mechanical arm. The upper portion and the lower portion are connected at the center of the vertical micro - spring structure and form a first corner facing horizontally. The MEMS actuator further includes a horizontal micro - spring structure disposed between one of the plurality of first micro - mechanical arms and one of the plurality of second micro - mechanical arms adjacent to the first micro - mechanical arm. The horizontal micro - spring structure further includes a first portion connected to the sidewall of the first micro - mechanical arm and a second portion connected to the sidewall of the second micro - mechanical arm. The first portion and the second portion are connected at the center of the horizontal micro - spring structure and form a second corner facing vertically.

[0204] In some embodiments, the vertical micro - spring structure further includes a first layer and a second layer vertically joined and stacked with each other; and the horizontal micro - spring structure further includes a third layer and a fourth layer vertically joined and stacked with each other.

[0205] In some embodiments, the first layer and the third layer are composed of an expansion material having a first coefficient of thermal expansion, the second layer and the fourth layer are composed of a compression material having a second coefficient of thermal expansion, and the first coefficient of thermal expansion is at least 10 times higher than the second coefficient of thermal expansion.

[0206] In some embodiments, the first layer and the third layer are a metal layer composed of an aluminum-copper alloy.

[0207] In some embodiments, the second layer and the fourth layer are an oxide layer composed of thermal silicon dioxide.

[0208] In some embodiments, an upper portion of the vertical microspring structure forms a first angle with the metal connection structure, a lower portion of the vertical microspring structure also forms a second angle with a top end of the one of the plurality of second micromechanical arms, a first portion of the horizontal microspring structure forms a third angle with the one of the plurality of first micromechanical arms, a second portion of the horizontal microspring structure forms a fourth angle with the one of the plurality of second micromechanical arms, and the first angle, the second angle, the third angle, and the fourth angle are at least 15 degrees.

[0209] According to some aspects of the present disclosure, a method for manufacturing a MEMS actuator is provided. In one embodiment, the method includes providing a substrate structure including a top wafer, a bottom wafer bonded to the top wafer, and a sacrificial portion. The method further includes forming trenches in the top wafer and forming a first protrusion and a second protrusion spaced apart from each other in the trenches; forming a plurality of first micro-mechanical arms and a plurality of second micro-mechanical arms. The plurality of first micro-mechanical arms and the plurality of second micro-mechanical arms are interposed, each of the plurality of first micro-mechanical arms and the plurality of second micro-mechanical arms extends from a top end to a bottom end, and one of the plurality of second micro-mechanical arms is disposed between the first protrusion and the second protrusion. The method further includes forming a first spacer, a second spacer, and an opening between the first spacer and the second spacer. The first spacer and the second spacer are respectively disposed on and in contact with the top surfaces of the first protrusion and the second protrusion, and the opening is vertically aligned with the one of the plurality of second micro-mechanical arms between the first protrusion and the second protrusion and is located on the one of the plurality of second micro-mechanical arms between the first protrusion and the second protrusion. The method further includes forming a vertical bilayer composite structure in the opening and disposed on the top end of the one of the plurality of second micro-mechanical arms between the first protrusion and the second protrusion. The vertical bilayer composite structure includes an oxide layer and a metal layer horizontally bonded to and stacked with the oxide layer. The method further includes forming a metal connection structure. The metal connection structure is connected to the top end of each of the plurality of first micro-mechanical arms, and an internal connection is made between the metal connection structure and the top end of the one of the plurality of second micro-mechanical arms between the first protrusion and the second protrusion within the vertical bilayer composite structure. The method further includes removing the sacrificial portion, the first spacer, the second spacer, and the first protrusion and the second protrusion of the substrate structure to form a cavity in the substrate structure, and the vertical bilayer composite structure is disposed in the cavity. The method further includes performing an annealing process to transform the vertical bilayer composite structure into a vertical micro-spring structure.

[0210] In some embodiments, the method further includes forming a passivation layer on the metal connection structure.

[0211] In some embodiments, the metal layer is composed of aluminum copper.

[0212] According to some embodiments of the present disclosure, a MEMS actuator is provided, including: a plurality of first micro mechanical arms and a plurality of second micro mechanical arms spaced apart from each other, wherein the plurality of first micro mechanical arms and the plurality of second micro mechanical arms are interleaved, each of the plurality of first micro mechanical arms and the plurality of second micro mechanical arms extends downward from a top end to a bottom end, and one of the plurality of second micro mechanical arms is disposed between two of the plurality of first micro mechanical arms; a metal connection structure connected to the top end of each of the plurality of first micro mechanical arms; and a vertical micro spring structure disposed and internally connected to the top end of the one of the plurality of second micro mechanical arms.

[0213] The foregoing has outlined features of several embodiments so that those skilled in the art may better understand various aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for achieving the same purposes and / or achieving the same advantages as those introduced herein. Those skilled in the art should also recognize that such equivalent constructs do not depart from the spirit and scope of the present disclosure, and various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of the present disclosure.

Claims

1. A micro-electromechanical system actuator, characterized in that: include: a first micro-mechanical arm array, comprising a plurality of first micro-mechanical arms spaced apart from each other in a first horizontal direction and extending in a second horizontal direction; a second micromechanical arm array, comprising a plurality of second micromechanical arms spaced apart from each other in the first horizontal direction and extending in the second horizontal direction, wherein the first micromechanical arm array and the second micromechanical arm array are interposed in the first horizontal direction; a metal connection structure extending in the first horizontal direction, wherein the metal connection structure is connected to a top end of each of the plurality of first micromechanical arms; and A vertical micro-spring structure is disposed between the metal connection structure and one of the plurality of second micro-mechanical arms, wherein the vertical micro-spring structure comprises: an upper portion connected to the metal connection structure; and a lower portion connected to a top end of the one of the plurality of second micro-mechanical arms, The upper portion and the lower portion are connected at a center of the vertical microspring structure and form a first corner facing horizontally.

2. The MEMS actuator according to claim 1, wherein: The vertical micro-spring structure further includes a first layer and a second layer which are joined and stacked with each other in the first horizontal direction.

3. The MEMS actuator according to claim 1 or 2, characterized in that: The first corner has an angle of 15 to 170 degrees.

4. The MEMS actuator according to claim 1 or 2, characterized in that: The upper portion and the metal connection structure form a first angle, the lower portion and the top of one of the plurality of second micromechanical arms form a second angle, and the first angle and the second angle are at least 15 degrees.

5. The MEMS actuator according to claim 1 or 2, characterized in that: The vertical microspring structure has a critical dimension of at least 1 μm in the first horizontal direction.

6. The MEMS actuator according to claim 1 or 2, characterized in that: The vertical microspring structure has a vertical dimension of at least 1.6 μm.

7. A micro-electromechanical system actuator, characterized in that: include: a first micro-mechanical arm array, comprising a plurality of first micro-mechanical arms spaced apart from each other in a first horizontal direction and extending in a second horizontal direction; a second micromechanical arm array, comprising a plurality of second micromechanical arms spaced apart from each other in the first horizontal direction and extending in the second horizontal direction, wherein the first micromechanical arm array and the second micromechanical arm array are interposed in the first horizontal direction; a metal connection structure extending in the first horizontal direction, wherein the metal connection structure is connected to a top end of each of the plurality of first micromechanical arms; A vertical micro-spring structure is disposed between the metal connection structure and at least one of the plurality of second micro-mechanical arms, wherein the vertical micro-spring structure comprises: an upper portion connected to the metal connection structure; and a lower portion connected to a top end of the one of the plurality of second micro-mechanical arms, wherein the upper portion and the lower portion are connected at a center of the vertical microspring structure and form a first corner facing horizontally; and a horizontal micro-spring structure disposed between one of the plurality of first micro-mechanical arms and one of the plurality of second micro-mechanical arms adjacent to the plurality of first micro-mechanical arms, wherein the horizontal micro-spring structure further comprises: a first portion connected to a side wall of the one of the plurality of first micro-mechanical arms; and a second portion connected to a side wall of the one of the plurality of second micro-mechanical arms; The first portion and the second portion are connected at a center of the horizontal micro-spring structure and form a second corner facing vertically.

8. The MEMS actuator according to claim 7, characterized in that: in The vertical microspring structure also includes a first layer and a second layer vertically joined and stacked with each other; and The horizontal microspring structure further includes a third layer and a fourth layer vertically joined and stacked with each other.

9. The MEMS actuator according to claim 7 or 8, characterized in that: The upper portion of the vertical microspring structure forms a first angle with the metal connection structure, the lower portion of the vertical microspring structure also forms a second angle with the top end of one of the plurality of second micromechanical arms, the first portion of the horizontal microspring structure forms a third angle with one of the plurality of first micromechanical arms, the second portion of the horizontal microspring structure forms a fourth angle with one of the plurality of second micromechanical arms, and the first angle, the second angle, the third angle and the fourth angle are at least 15 degrees.

10. A micro-electromechanical system actuator, characterized in that: include: A plurality of first micromechanical arms and a plurality of second micromechanical arms spaced apart from each other, wherein the plurality of first micromechanical arms are interposed with the plurality of second micromechanical arms, each of the plurality of first micromechanical arms and the plurality of second micromechanical arms extends downward from a top end to a bottom end, and one of the plurality of second micromechanical arms is disposed between two of the plurality of first micromechanical arms; a metal connection structure connected to the top end of each of the plurality of first micro-mechanical arms; and A vertical micro spring structure is disposed and internally connected to the top end of the one of the plurality of second micro mechanical arms.

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