Method for making micromechanical arm array for MEMS actuator and MEMS actuator

Abstract

Microelectromechanical systems (MEMS) structures can be used as actuators for moving image sensors to achieve optical image stabilization. MEMS actuators include one or more micro-manipulator arrays. Each array includes a first array of spaced fingers formed of a piezoelectric material and a second array of spaced fingers formed of a conductive material. The distal ends of the first and second finger arrays are interposed between each other. Microsprings connect the interposed distal ends of each pair of adjacent fingers together. Metal caps are located above the distal ends of the first and second finger arrays. The microsprings connect the metal caps to the distal ends of each finger in the first finger array. This structure increases stability and strength.

Description

[Technical Field]

[0001] None [Previous Technology]

[0002] Micro-electromechanical systems (MEMS) are a technology that uses miniature mechanical and electromechanical components (e.g., devices or structures) on a wafer substrate. Devices or structures that can be used in MEMS include sensors, actuators, and other structures. MEMS devices can be used in a wide range of applications, including but not limited to optical / imaging devices.

[0003] Microelectromechanical systems (MEMS) structures can be fabricated using a photolithography process, which uses ultraviolet light to transfer the desired mask pattern onto a photoresist layer on a semiconductor wafer. The pattern can then be transferred to a layer beneath the photoresist using an etching process. This process can be repeated multiple times with different patterns to build different layers on the wafer substrate and fabricate useful devices. [Summary of the Invention]

[0004] None

Implementation Method

[0006] The following disclosure provides many different implementations or examples for achieving different features of the provided object. Specific examples of elements and compositions are described below to simplify this disclosure. Of course, these are merely examples and are not intended to limit this disclosure. For example, in the following description, forming a first feature on or above a second feature may include implementations where the first and second features are formed in direct contact, or implementations where additional features can be formed between the first and second features, thus the first and second features are not in direct contact. Furthermore, this disclosure may repeat schematic symbols and / or letters in various examples. Such repetition is for simplicity and clarity and does not in itself specify the relationship between the various implementations and / or configurations discussed.

[0007] Furthermore, for ease of description, this document may use spatially relative terms such as "below," "below," "lower part," "above," "over," etc., to describe the relationship between one element or feature shown in the figures and another element or feature. In addition to the orientations described in the figures, spatially relative terms are also intended to include different orientations of the device during use or operation. The device may be oriented in other ways (rotated 90 degrees or rotated in other directions), and the spatially relative terms used herein may be interpreted accordingly.

[0008] The numerical values ​​in this application specification and claims should be understood to include values ​​that remain the same when significant figures are reduced to the same number, as well as values ​​that differ from the stated values ​​by less than the experimental error of the conventional measurements performed to determine the values ​​as described in this application. All scopes of this disclosure include the referenced endpoints.

[0009] The term "approximately" can include any numerical value that can vary without altering its basic function. When used with a range, "approximately" also reveals a range defined by the absolute values ​​of its two endpoints; for example, "approximately 2 to approximately 4" reveals a range "from 2 to 4". The term "approximately" can be plus or minus 10% of a specified numerical value.

[0010] This disclosure relates to structures composed of different layers. When the terms "on" or "above" are used to refer to two different layers (including a substrate), they may simply mean that one layer is on or above another. These terms do not require that the two layers be in direct contact with each other and allow other layers to be located between the two layers. For example, all layers in a structure may be considered to be located "on" the substrate, even if they are not in direct contact with the substrate. The term "direct" may be used to indicate that two layers are in direct contact with each other and there are no other layers between them. Furthermore, when referring to performing process steps on or on a substrate, this should be understood as performing such steps on any layers that may be present on the substrate, depending on the context.

[0011] This disclosure specifically relates to micro-robotic arm arrays for use as microelectromechanical system (MEMS) actuators. MEMS actuators convert electrical signals into mechanical signals and are typically electrically connected to other integrated circuits (ICs) to form a system. Such actuators are commonly used in optical image-capturing devices, such as cameras that can be used as part of a standalone handheld camera or mobile phone. However, micro-robotic arm arrays can be damaged, for example, due to impacts / shocks, such as when falling from a height.

[0012] This disclosure discloses a novel micromanipulator array with improved stability and strength. The micromanipulator array includes two finger arrays, each extending from one arm. In some embodiments, one array is made of a piezoelectric material. The other array is made of a non-piezoelectric conductive material, such as polycrystalline silicon. Microsprings are present between adjacent fingers and also between the metal cap and the piezoelectric finger array. In other embodiments, the ratio of the number of fingers in the first finger array to the number of fingers in the second finger array is an integer greater than 1. Furthermore, the lifespan of the springs is improved.

[0013] Figure 1 is a side cross-sectional view of a first exemplary embodiment of a package 100 including a micro-mechanical system micromanipulator array 148 according to some embodiments of the present disclosure.

[0014] Package 100 includes a top wafer 110 (also called a device wafer) and a bottom wafer 120 (also called a handle wafer), which are bonded together by a bonding layer 130. This package is also called a silicon-on-insulator (SOI) substrate.

[0015] Next, a micro-manipulator array 148 exists in the top wafer 110. The top wafer 110 has multiple portions in the horizontal direction, labeled as anchor arm portion 132, drive comb portion 134, hinge portion 136, inner frame portion 138, spring portion 140, and outer frame portion 142. The micro-manipulator array 148 is located in the drive comb portion 134. These different portions together constitute the quadrant of the microelectromechanical system actuator (discussed later herein).

[0016] Anchor arm portion 132 provides structural integrity and helps support the drive comb portion. Pivot portion 136 allows the pivot to operate, or allows controlled rotation relative to other elements of the drive comb portion. Inner frame portion 138 provides structural support and stability. Spring portion 140 provides elasticity to maintain the required positioning and movement of the elements, and also provides a restoring force for the elements to return to their original position after being actuated. Outer frame portion 142 generally provides structural integrity to protect the internal elements from external and environmental forces.

[0017] A cavity 112 exists within the top wafer 110. A micro-robotic arm array 148 is disposed within the cavity and can move freely within it. The cavity also extends continuously below the hub portion 136, the inner frame portion 138, and the spring portion 140. Two smaller cavities 122 also exist within the bottom wafer 120, and they are generally located below the hub portion 136, the inner frame portion 138, and the spring portion 140. The cavity 112 in the top wafer 110 is connected to the two smaller cavities 122 in the bottom wafer 120.

[0018] The micromanipulator array includes two separate arrays formed by multiple fingers, namely a first finger array 150 (or a first piezoelectric finger array) and a second finger array 170 (or a second conductive finger array). The piezoelectric fingers are separated from each other. Similarly, the conductive fingers are also separated from each other. As shown in the figure, two piezoelectric fingers of the first finger array 150 are inserted between two conductive fingers of the second finger array 170.

[0019] A metal cap 190 is present above the first finger array 150 and the second finger array 170. The first finger array 150 is connected to the metal cap 190 by a "vertical" microspring 202. In addition, a "horizontal" microspring 204 is present between adjacent fingers in the first finger array 150 and the second finger array 170.

[0020] Figure 2 is an enlarged side cross-sectional view of the micro-robotic arm array 148. It should be noted that this is a simplified schematic diagram for illustrative purposes only and is not intended to fully represent the complete micro-robotic arm array 148.

[0021] As shown in the figure, each piezoelectric finger of the first finger array 150 includes a core 152 formed of a piezoelectric material. A capping layer 154 is present around all sides of the core 152 and isolates the core from the cavity. The capping layer may act as an etch stop layer and is typically made of a dielectric material. Each piezoelectric finger also has a free end 156 (or bottom end) and a fixed end 158 (or top end). In this view, the piezoelectric finger has a height 163 and a width 165.

[0022] Similarly, each conductive finger in the second finger array 170 includes a core 172 formed of a non-piezoelectric conductive material. A capping layer 174 is present around all sides of the core 172 and isolates the core from the cavity. The capping layer may act as an etch stop layer and is typically made of a dielectric material. Each conductive finger also has a free end 176 (or bottom end) and a fixed end 178 (or top end). The conductive fingers have a height 183 and a width 185. In some specific embodiments, the conductive fingers in the second finger array 170 are made of polycrystalline silicon, while the capping layer is formed of silicon dioxide (SiO2).

[0023] As shown in the figure, the height 183 of the conductive fingers is greater than the height 163 of the piezoelectric fingers. In some specific embodiments, the heights 183 and 163 can independently be from about 150 micrometers (μm) to about 200 μm. Other ranges are also within the scope of this disclosure. Similarly, the width 185 of the conductive fingers is greater than the width 165 of the piezoelectric fingers. However, such dimensions may be unnecessary for the operation of the micro-robotic arm array, and the trend in dimensions may be reversed. Furthermore, the fingers in the first finger array 150 and the second finger array 170 are illustrated with their top surfaces at the same height or horizontal plane. Again, this may not be necessary for the operation of the micro-robotic arm array.

[0024] A passivation layer 200 is present on the top surface 192 of the metal cap. As shown, the metal cap 190 directly contacts the fixed end 178 of the second finger array 170, but not the fixed end 158 of the first finger array 150. Instead, the fixed end of the first finger array 150 is connected to the metal cap 190 by a "vertical" microspring 202. The opposite arrangement is also conceivable, where the metal cap 190 directly contacts the first finger array 150, and the second finger array 170 is connected to the metal cap 190 by a "vertical" microspring 202. A "horizontal" microspring 204 exists between adjacent fingers in the first finger array 150 and the second finger array 170. The free ends 156 and 176 in the two finger arrays can move freely under the metal cap.

[0025] Each microspring is made of a combination of two layers: a metal layer 206 and a dielectric layer 208. In some embodiments, the metal layer 206 is a metal or metal alloy, such as, but not limited to, aluminum (Al) or aluminum alloys (e.g., AlCu); copper (Cu); tungsten (W); or nickel (Ni). In some embodiments, the dielectric layer is made of silicon dioxide (SiO2), although other materials may also be used. Generally, the two layers have different or opposite tensile properties, thus providing vibration isolation, resonance control, damping, and energy dissipation. This also reduces the energy transmitted to the fingers due to external impacts. In some embodiments, the length 209 of the microsprings 202 and 204 may be about 1.6 micrometers (μm) or longer, although other ranges are also within the scope of this disclosure. This corresponds to the distance between adjacent fingers. In some embodiments, the distance between two adjacent piezoelectric fingers is different from the distance between a piezoelectric finger in the first finger array 150 and a conductive finger adjacent to it in the second finger array 170.

[0026] Figure 3A is a plan view of the micro-robotic arm array in Figure 2. Similarly, this is a simplified schematic diagram for illustrative purposes only and is not intended to fully represent the complete micro-robotic arm array 148.

[0027] As shown in the figure, piezoelectric fingers extend from a distal end 160 along a first direction 214 to a proximal end 162 connected to a first arm 168. In other words, the piezoelectric fingers in the first finger array 150 extend from the first arm. The first arm is also made of piezoelectric material and is covered by a capping layer (not shown here). Conductive fingers extend from a distal end 180 along a second direction 216 opposite to the first direction to a proximal end 182 connected to a second arm 188. In other words, the conductive fingers in the second finger array 170 extend from the second arm. The second arm is also made of conductive material and is covered by a capping layer (not shown here). The fingers in the first finger array 150 and the second finger array 170 extend along a first horizontal direction (i.e., axis X). The two arms, namely the first arm 168 and the second arm 188, extend along a second horizontal direction (i.e., axis Y, where axis X is perpendicular to axis Y, and axis Z is perpendicular to both axis X and axis Y). Although not illustrated here, the other ends of the two arms are connected to the anchor arm portion 132 and the outer frame portion 142.

[0028] The piezoelectric fingers in the first finger array 150 can be described as extending from the first arm 168 toward the conductive fingers in the second finger array 170, and vice versa. The distal ends 160 and 180 of the fingers in the first finger array 150 and the second finger array 170 are inserted into or interleaved with each other. In other words, the distal ends of the first finger array overlap with the distal ends of the second finger array. In some embodiments, the lengths 167 and 187 of the fingers in the first finger array 150 and the second finger array 170 can be from about 1 millimeter (mm) to about 3 mm, although other values ​​and ranges are also within the scope of this disclosure.

[0029] A "horizontal" micro-spring 204 connects the distal ends of adjacent fingers together. A metal cap 190 covers the distal ends and is shown as a dashed line in the figure. It should be noted that the first finger array 150 and the second finger array 170 of the micromanipulator array can have a large number of piezoelectric fingers and a large number of conductive fingers, without being limited by these schematic diagrams, such as those shown as consecutive dots in the figure. In the diagram, the ratio of piezoelectric fingers in the first finger array 150 to conductive fingers in the second finger array 170 is 2:1, i.e., the ratio is an integer of 2. The piezoelectric fingers are distributed such that there are two piezoelectric fingers grouped together between two conductive fingers.

[0030] Figure 3B is a plan view of a second embodiment of the micro-robotic arm array 148. In this embodiment, the ratio of piezoelectric fingers in the first finger array 150 to conductive fingers in the second finger array 170 is 1:1. There is one piezoelectric finger between two conductive fingers in a group.

[0031] Figure 3C is a plan view of a third embodiment of the micromanipulator array 148. In this embodiment, the ratio of piezoelectric fingers in the first finger array 150 to conductive fingers in the second finger array 170 is 3:1, i.e., the ratio is an integer of 3. There are three piezoelectric fingers between groups of two conductive fingers. Therefore, typically, the ratio of piezoelectric fingers in the first finger array 150 to conductive fingers in the second finger array 170 can range from about 1:1 or greater. The maximum ratio can be about 10:1. It should be noted that the "array" of fingers can include as few as one finger. Typically, each finger array can include from 1 finger to about 60 fingers, or about 100 fingers, or up to 1000 fingers, depending on the requirements.

[0032] Figures 4A through 4C collectively illustrate a flowchart of a first method 300 for manufacturing an array of micro-manipulators for a microelectromechanical system actuator, according to some embodiments. Some steps of this method are also illustrated in Figures 5 through 30B. These figures provide different views to better understand the contents of this disclosure. Although the method steps discussed below are for forming a single array of micro-manipulators with a small number of fingers, such discussion should also be interpreted broadly as applicable to forming multiple arrays of micro-manipulators in parallel at a single drive comb portion and forming a large number of fingers. These figures do not show the formation of the entire actuator, only the drive comb portion.

[0033] First, in step 302 of Figure 4A, as shown in Figure 5, the top wafer 110 is connected to the bottom wafer 120 to form package 100. Alternatively, as shown in step 304 of Figure 4A, the package is received.

[0034] The top wafer 110 and the bottom wafer 120 can be independently wafers made of, for example, semiconductor materials. Such semiconductor materials may include silicon, for example, in the form of crystalline silicon. In some alternative embodiments, the substrate may be made of other elemental semiconductors, such as germanium, or may include compound semiconductors such as silicon carbide (SiC), gallium arsenide (GaAs), gallium carbide, gallium phosphide, indium arsenide (InAs), indium phosphide (InP), silicon germanium, silicon germanium carbide, gallium arsenide phosphide, or gallium indium phosphide. In some specific embodiments, both wafers are made of silicon.

[0035] The top wafer includes a top surface 114, which also serves as the top surface of the package. Typically, the top wafer 110 has a relatively small thickness 115 (e.g., in the range of about 200 μm), making it very flexible and therefore difficult to process. The bottom wafer 120 has a relatively large thickness 125 (e.g., in the range of about 500 μm) to increase the overall thickness of the package, thereby providing mechanical stability during the processing and aiding in electrical isolation (if required). Two cavities 122 are already present in the bottom wafer 120. The bonding layer 130 can be formed by fusion bonding, for example, by a heating and / or pressing process without using any other additional layers. As another example, both wafers can have dielectric layers on suitable surfaces, and then the dielectric layers are heated and the two wafers are pressed together to form the bonding layer.

[0036] Next, in step 306 of Figure 4A, as shown in Figures 6A to 6D, the top wafer 110 is patterned to form a recess 220. A plurality of pillars 222 are formed within the recess. These pillars are spaced apart from each other. The pillars can be formed on the support 224 according to the required height of the fingers of the micromanipulator array. The recess is part of the drive comb portion 134. Additional trenches 135 are also formed in the drive comb portion. Additional trenches 137, 139, and 143 are also formed in the top wafer, and their positions will correspond to the hub portion, inner frame portion, spring portion, and outer frame portion. The pillars correspond to the positions where horizontal microsprings will be formed.

[0037] Figure 6A is a plan view of the package after the patterning / etching step. As shown, a recess is molded within the recess to form two different sets of trenches 230 and 232 to correspond to two different finger arrays. It is worth noting that a "set" of trenches may consist of as few as one trench. The different depths of the recess 220, the support (see trench 230), and the pillar 222 are illustrated with different dot patterns. Figure 6B is a side cross-sectional view of the package in Figure 6A along line BB. This cross-section passes through the distal ends of the fingers and the location where the microsprings will be formed. Figure 6C is a side cross-sectional view of the package in Figure 6A along line CC. In this cross-section, only the trenches 230 of the first finger array are visible in the recess 220. Figure 6D is a side cross-sectional view of the package in Figure 6A along line DD. In this cross-section, only the trenches 232 of the second finger array are visible in the recess 220. It should be noted that the cross-sectional views in Figures 7 to 30B are along line BB in Figure 6A.

[0038] Next, in step 308 of Figure 4A, as shown in Figure 7, a first dielectric layer 240 is formed on the exposed surface of the recess 220. The first dielectric layer is also formed on other exposed surfaces of the top wafer 110, including on the top surface 114. In some specific embodiments, the first dielectric layer is made of silicon dioxide (SiO2) and can be formed by thermally oxidizing a silicon wafer. Of particular note is that a portion of the first dielectric layer 240 on the pillar 222 will form a horizontally oriented dielectric layer 208 for microsprings.

[0039] Next, in step 310 of Figure 4A, as shown in Figure 8, metal 242 is deposited on the top wafer. Then, in step 312 of Figure 4A, as shown in Figures 9A and 9B, the metal is patterned to form a metal layer 206 on each pillar 222. This metal layer will form a second layer of horizontal microsprings. In some specific embodiments, the metal is aluminum (Al) or an aluminum alloy, such as AlCu. The metal can be deposited by vapor deposition or sputtering, plating, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), or other suitable methods. As shown in Figure 9B, the metal layer 206 is present only on the pillars 222 and not in the trenches 230 and 232 within the recesses. The combination of the dielectric layer 208 and the metal layer 206 on each pillar is also referred to herein as the microspring precursor structure 210 or the horizontal composite structure.

[0040] Next, in step 314 of Figure 4A, as shown in Figure 10, sacrificial material 244 is deposited on the top wafer, including within the recess 220. The sacrificial material can be deposited using CVD, PVD, or other suitable methods. Next, in step 316 of Figure 4A, as shown in Figures 11A and 11B, the sacrificial material is patterned to form sacrificial spacers 246 on each pillar. As shown in Figure 11B, the sacrificial spacers 246 are formed only on the pillars 222 and not in other areas of the recess. In some specific embodiments, the sacrificial material is the same material as the top wafer, such as silicon.

[0041] In step 318 of Figure 4A, as shown in Figure 12, a dielectric layer is formed on the exposed surfaces of the metal layer 206 and the sacrificial spacer 246. This step can be considered as increasing the first dielectric layer 240. In some specific embodiments, this is accomplished by performing thermal oxidation on the exposed surfaces. Thus, the first set of trenches 230 and the second set of trenches 232 are completely separated from each other within the grooves.

[0042] Next, in step 320 of Figure 4A, as shown in Figures 13A and 13B, piezoelectric material 252 is deposited into the trenches of the first group to form the first finger array 150. Referring to Figures 3A to 3C, the first arm 168 is also formed in this step. The deposition can be performed using CVD, PVD, or other suitable methods. Examples of suitable piezoelectric materials may include barium titanate (BaTiO3, BTO), lead titanate (PbTiO3), lead zirconate titanate (PZT), or potassium sodium niobate (KNN).

[0043] Next, in step 322 of Figure 4A, as shown in Figure 14, conductive material is deposited into the trenches of the second group to form the second finger array 170. Referring to Figures 3A to 3C, the second arm 188 is also formed in this step. Deposition can be performed using CVD, PVD, or other suitable methods. This conductive material is not a piezoelectric material. As shown, a conductive material layer 254 is also formed on the top wafer, including the piezoelectric fingers formed in the first finger array 150. In some specific embodiments, the conductive material is polycrystalline silicon.

[0044] In step 324 of Figure 4A, as shown in Figures 15A and 15B, the conductive material layer is planarized to the location of the first dielectric layer 240. The first dielectric layer acts as an etch stop layer for this step. As shown, after the planarization step, the conductive material layer 254 remains on the piezoelectric fingers in the first finger array 150 in the first set of trenches. As can be seen in Figure 15B, the distal ends 160 and 180 of the two finger arrays are interposed between each other.

[0045] In step 326 of Figure 4A, as shown in Figure 16, the conductive material layer 254 is further patterned to expose the fingers in the two arrays (the first finger array 150 and the second finger array 170). In other words, the horizontal plane of the conductive material is lowered below the horizontal plane of the first dielectric layer 240. The horizontal plane of the conductive material is also lowered in the other trenches 135, 137, 139, and 143 in the top wafer.

[0046] Next, in step 328 of Figure 4B, as shown in Figure 17, a dielectric layer is formed on the exposed surfaces of the piezoelectric material 252 and the conductive material layer 254. This step can be considered as adding a first dielectric layer 240. In some specific embodiments, this is accomplished by performing thermal oxidation on the exposed surfaces. The operation of adding the first dielectric layer also occurs on other trenches 135, trench 137, trench 139, and trench 143 in the top wafer.

[0047] Next, in step 330 of Figure 4B, as shown in Figure 18, the first dielectric layer 240 is patterned to expose a portion of the top wafer 110 within the drive comb portion 134. As will be shown later, this is done so that silicon can be removed later. A portion of the first dielectric layer is removed from the drive comb portion to expose the top wafer.

[0048] Next, in step 332 of Figure 4B, as shown in Figure 19, a first etch stop layer 256 is deposited on the top wafer. Deposition can be performed using CVD, PVD, or other suitable methods. The first etch stop layer can be made of any material different from the first dielectric layer 240, such as different dielectric or conductive materials. In some specific embodiments, the first etch stop layer is made of polysilicon.

[0049] In step 334 of Figure 4B, as shown in Figure 20, a second dielectric layer 258 is formed on the first etch stop layer 256. This can be accomplished by deposition (e.g., CVD, PVD, or other suitable methods). Next, in step 336 of Figure 4B, as shown in Figures 21A and 21B, the second dielectric layer is patterned to expose a portion of the drive comb portion 134, the hub portion 136, and the inner frame portion 138. In other words, the second dielectric layer is removed from these three portions. Thus, the second dielectric layer 258 remains on a portion of the inner frame portion 138, the spring portion 140, and the outer frame portion 142. In the spring portion 140, the second dielectric layer 258 is present on a central portion 102 aligned with the distal ends of the fingers in the first finger array 150 and the second finger array 170. The first etch stop layer 256 is exposed where the second dielectric layer has been removed. Typically, the first dielectric layer 240 and the second dielectric layer 258 are made of the same material.

[0050] Next, in step 338 of Figure 4B, as shown in Figure 22, the second etch stop layer 260 is deposited on the top wafer. Deposition can be performed using CVD, PVD, or other suitable methods. In some specific embodiments, the second etch stop layer is made of the same material as the first etch stop layer 256. As shown, the first etch stop layer 256 and the second etch stop layer 260 are in direct contact with each other at multiple locations in the anchor arm portion 132, the drive comb portion 134, the hub portion 136, and the inner frame portion 138.

[0051] Next, in step 340 of Figure 4B, as shown in Figures 23A and 23B, two etch stop layers are patterned to form vertical spacers 262 within the drive comb portion. As shown, the spacers 262 are present on a portion of the top wafer 110 located between the first finger array 150 and the second finger array 170 in the drive comb portion 134 and the trench 135. The trench 264 is present between these spacers and is located above the distal end of the first finger array 150 in the drive comb portion 134. The spacers 262 are also present on the first dielectric layer 240 adjacent to the drive comb portion 134. As shown in Figure 23B, the second etch stop layer 260 can also be seen on either side of the central portion 102 in the spring portion 140, aligned with the distal ends of the fingers in the first finger array 150 and the second finger array 170.

[0052] In step 342 of Figure 4B, as shown in Figure 24, a third dielectric layer 270 is deposited on the top wafer 110. Deposition can be performed using CVD, PVD, or other suitable methods. Next, in step 344 of Figure 4B, as shown in Figures 25A and 25B, the third dielectric layer is patterned to form a vertical dielectric layer 208 in each trench 264. Additionally, the third dielectric layer on the top surface of the top wafer is removed.

[0053] In step 346 of Figure 4B, as shown in Figure 26, metal layer 272 is deposited on top wafer 110. Deposition can be performed using CVD, PVD, or other suitable methods. Next, in step 348 of Figure 4B, as shown in Figures 27A and 27B, the metal layer is patterned to form a vertical metal layer 206 in each trench 264. This vertical metal layer is adjacent to and in direct contact with a vertical oxide layer in the trench. The combination of the vertical metal layer 206 and the vertical oxide layer, or dielectric layer 208, is also referred to herein as a microspring precursor structure 212 or a vertical composite structure.

[0054] As shown in Figure 27B, the metal layer 272 is also patterned to form metal caps 190 on the distal ends of the first finger array 150 and the second finger array 170. The metal layer is also patterned and retained in the central portion 102 of other grooves 135, 137, 139, and 143 in the drive comb portion 134, the pivot portion 136, the inner frame portion 138, the spring portion 140, and the outer frame portion 142. Notably, the metal layer 272 has two different heights, which can be obtained by two consecutive masking / etching steps. The location of the microspring precursor structure 212 is illustrated for reference.

[0055] Next, in step 350 of Figure 4C, as shown in Figures 28A and 28B, a passivation layer 200 is formed on the metal cap 190. The passivation layer 200 is also formed on the metal layer 272 in the drive comb portion 134, the hub portion 136, the inner frame portion 138, the spring portion 140, and the outer frame portion 142. The passivation layer can be formed by depositing a fourth dielectric layer and performing a patterning process to remove the fourth dielectric layer from unwanted locations. Although not shown, the passivation layer is also present on the sides of the metal cap 190 and the metal layer 272.

[0056] Next, in step 352 of Figure 4C, as shown in Figures 29A and 29B, a cavity 112 is formed in the top wafer 110 below the first finger array 150 and the second finger array 170. For example, this can be achieved by patterning the top wafer and then using a dry etching process to etch through the exposed vertical spacers 262 and the first dielectric layer 240 below the vertical spacers (see Figures 28A and 28B), followed by a wet etching process to etch silicon. The wet etching process can be controlled using timing. After the wet etchant has etched through the top wafer, the cavity 122 in the bottom wafer provides a volume for collecting and neutralizing the wet etchant. The material of the top wafer in the hub portion 136 and the spring portion 140 is also etched. Some undercutting may occur, but this is acceptable. The result of this etching step is that the microspring precursor structure 210 and the microspring precursor structure 212 are released from the top wafer and the two etch stop layers. When viewed from above, portions of the bonding layer 130 and the bottom wafer 120 are also visible.

[0057] Next, in step 354 of Figure 4C, annealing is performed. The annealing step can be performed in a heating chamber at a high temperature (e.g., from about 800 °C to about 1,600 °C). Therefore, microsprings 202 and 204 are formed from microspring precursor structures. The resulting micromanipulator array 148 is shown in Figure 1.

[0058] In some embodiments, the package shown in Figure 1 can be used as part of a microelectromechanical system actuator. In other embodiments, the bottom wafer 120 is subsequently removed or separated from the top wafer 110. This is indicated as optional step 356 in Figure 4C, and the resulting structure is illustrated in Figures 30A and 30B.

[0059] Any metallic layer discussed herein can generally be formed from any conductive metal or conductive oxide. Examples of suitable metals may include copper, aluminum, nickel, chromium, gold, germanium, silver, titanium, tungsten, platinum, tantalum, ruthenium, cobalt, rhenium, palladium, or zirconium; compounds such as TiN, WN, or TaN; or alloys of the foregoing, such as AlCu. Examples of suitable conductive oxides may include indium tin oxide (ITO), zinc oxide (ZnO), tin oxide (SnO), zinc aluminum oxide (AlZnO), indium oxide (InO), or cadmium oxide (CdO). The metal or oxide material can be deposited by, for example, evaporation or sputtering, coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), or other suitable methods.

[0060] The structure and method disclosed herein also involve several different dielectric layers. Such dielectric layers can generally be made by any suitable dielectric material or combination thereof, although the properties of any particular layer may be further defined. Examples of dielectric materials may include silicon dioxide (SiO 2), silicon nitride (Si 3N 4), silicon carbide (SiC), hafnium dioxide (HfO 2), zirconium dioxide (ZrO 2), aluminum oxide (Al 2O 3), silicon oxynitride (SiO xN y), hafnium oxynitride (HfO xN y) or zirconium oxynitride (ZrO xN y), hafnium silicate (HfSi xO y) or zirconium silicate (ZrSi xO y) or silicon carbonitride (SiC xO yN z), or hexagonal boron nitride (hBN). Other dielectric materials may include tantalum oxide (Ta₂O₅), silicon nitrides such as polycrystalline silicon, phosphosilicate glass (PSG), fluorosilicate glass (FSG), undoped silicate glass (USG), high-stress undoped silicate glass (HSUSG), and borosilicate glass (BSG). The dielectric layer can be formed by any suitable method, including chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), thermal oxidation, or other suitable methods.

[0061] It should also be noted that some conventional steps are not explicitly described in the above discussion. For example, a pattern / structure can be formed in a predetermined layer by applying a photoresist layer, patterning the photoresist layer, developing the photoresist layer, and then performing etching to transfer the pattern to the predetermined layer.

[0062] Generally, the photoresist layer can be applied, for example, by spin coating or spraying, roller coating, dip coating, or extrusion coating. Typically, in spin coating, the substrate is placed on a rotating plate, which may include a vacuum chuck to hold the substrate on the plate. The photoresist composition is then applied to the center of the substrate. The photoresist is then evenly distributed from the center of the substrate to its periphery by increasing the speed of the rotating plate. The rotational speed of the plate is then fixed to control the final thickness of the photoresist layer.

[0063] Next, the photoresist composition is baked or cured to remove the solvent and harden the photoresist layer. In some specific embodiments, baking occurs at a temperature of about 90 °C to about 110 °C. Baking can be performed using a hot plate or oven or similar apparatus. Thus, a photoresist layer is formed on the substrate.

[0064] The photoresist layer is then patterned by exposure to radiation. The radiation can be light of any wavelength with the desired mask pattern. In some specific embodiments, extreme ultraviolet (EUV) light with a wavelength of about 13.5 nm is used to perform the patterning process because this allows for smaller feature sizes. Some portions of the photoresist layer are exposed to radiation, while other portions are not. The exposure causes some portions of the photoresist to become soluble in the developer, while other portions remain insoluble.

[0065] After exposure to radiation, an additional photoresist baking step (post-exposure bake, PEB) may be performed. For example, this helps to release acid leaving group (ALG) or other molecules that are important in chemically amplified photoresists.

[0066] Next, the photoresist layer is developed using a developer. The developer can be an aqueous solution or an organic solvent. During the development step, the soluble portion of the photoresist layer is dissolved and washed away to leave the photoresist pattern. A common example of a developer is an aqueous solution of tetramethylammonium hydroxide (TMAH). Generally, any suitable developer can be used. Sometimes, baking, or "hard baking," can be performed after development to stabilize the developed photoresist pattern and facilitate optimal performance in subsequent steps.

[0067] Next, a portion of the predetermined layer beneath the patterned photoresist layer is exposed. Etching transfers the photoresist pattern to the predetermined layer beneath the patterned photoresist layer. After using the patterned photoresist layer, the patterned photoresist layer can be removed, for example, by using various solvents at high temperatures, such as N-methyl-pyrrolidone (NMP) or alkaline media or other stripping agents, or by a dry etching process using oxygen plasma.

[0068] Generally speaking, any etching step described herein may be performed using wet etching, dry etching, plasma etching, or a combination thereof, as appropriate, such as using reactive ion etching (RIE) or inductively coupled plasma (ICP). Etching may be anisotropic. Depending on the material, etchants may include carbon tetrafluoride (CF4), hexafluoroethane (C2F6), octafluoropropane (C3F8), fluoroform (CHF3), difluoromethane (CH2F2), fluoromethane (CH3F), fluorinated carbon, nitrogen (N2), hydrogen (H2), oxygen (O2), argon (Ar), xenon (Xe), xenon difluoride (XeF2), helium (He), carbon monoxide (CO), carbon dioxide (CO2), fluorine (F2), chlorine (Cl2), hydrogen bromide (HBr), hydrofluoric acid (HF), nitrogen trifluoride (NF3), sulfur hexafluoride (SF6), boron trichloride (BCl3), ammonia (NH3), bromine (Br2), or similar substances, or combinations thereof in various proportions. For example, hydrofluoric acid and ammonium fluoride can be used to perform wet etching on silicon dioxide. Alternatively, dry etching of silicon dioxide can be performed using various mixtures of CHF3, O2, CF4 and / or H2.

[0069] Next, Figure 31A shows a flowchart of a more general method 360 for manufacturing a micromanipulator array for a microelectromechanical system actuator, according to some embodiments. In step 362 of Figure 31A, the first finger array 150 is formed from a piezoelectric material on the top wafer 110. This structure is shown in Figures 13A and 13B.

[0070] In step 364 of Figure 31A, the second finger array 170 is formed from a conductive material on the top wafer 110. The distal ends 160 of the first finger array and the distal ends 180 of the second finger array are interposed between each other. This structure is shown in Figures 15A and 15B.

[0071] In step 366 of Figure 31A, microspring precursor structures 210 and 212 are formed between the distal ends 160 and 180 of adjacent fingers and on each finger of the first finger array (at its distal end 160). The microspring precursor structure 210 can also be described as being formed on a post 222 located at the ends of the two sets of grooves 230 and 232. This structure is shown in Figures 9A and 9B.

[0072] In step 368 of Figure 31A, a metal cap 190 is formed, which contacts each finger in the second finger array 170 and each microspring precursor structure 212 on the first finger array. This structure is shown in Figures 27A and 27B.

[0073] In step 370 of Figure 31A, the top wafer 110 is etched to form a cavity 112 below the first finger array and the second finger array. This structure is shown in Figures 29A and 29B. Notably, the microspring precursor structure 210 and the microspring precursor structure 212 are exposed at this time.

[0074] In step 372 of Figure 31A, annealing is performed to convert each microspring precursor structure into microspring 202 and microspring 204. The resulting structure is shown in Figure 1.

[0075] Next, Figure 31B shows a flowchart of another general method 380 for manufacturing a micromanipulator array for a microelectromechanical system actuator, according to some embodiments. This method is substantially similar to that of Figure 31A. However, in this method, the ratio of the number of fingers in the first finger array to the number of fingers in the second finger array is at least 2:1 and can be in the range of 10:1. In other words, if the number of the first fingers is divided by the number of the second fingers, the quotient is an integer of at least 2. Therefore, both the first finger array 150 and the second finger array 170 can be made of piezoelectric material, or both can be made of non-piezoelectric conductive material.

[0076] In step 382 of Figure 31B, a first finger array 150 is formed on the top wafer 110. In step 384, a second finger array 170 is formed on the top wafer 110. The distal ends 160 of the first finger array and the distal ends 180 of the second finger array are interposed between each other. This structure is shown in Figures 15A and 15B. In some specific embodiments, as described above, the ratio of the number of fingers in the first finger array 150 to the number of fingers in the second finger array 170 is at least 2.

[0077] In step 386 of Figure 31B, microspring precursor structures 210 and 212 are formed between the distal ends 160 and 180 of adjacent fingers and on each finger of the first finger array (at its distal end 160). In step 388, a metal cap 190 is formed, which contacts each finger in the second finger array 170 and each microspring precursor structure 212 on the first finger array. In step 390, the top wafer 110 is etched to form a cavity 112 below the first and second finger arrays. In step 392, annealing is performed to convert each microspring precursor structure into microsprings 202 and 204. The resulting structure is shown in Figure 1.

[0078] Next, Figure 32 is a plan view of a microelectromechanical system actuator 400 according to some embodiments. The actuator shown includes a four-sided frame 402 that surrounds and is spaced apart from a sensor connection element 404. The sensor connection element 404 includes a centrally located anchor 406. As shown, four anchor arms 407 extend from the anchor, and together they are considered as an anchor structure 408.

[0079] The sensor connection element can be described as having four quadrants, each located between two anchor arms. Within each quadrant, anchor arms 407 support one or more micro-robotic arm arrays 148 within a drive comb section 134, as previously described. As shown, the drive comb section includes two micro-robotic arm arrays, but any number of such arrays may exist. In some specific embodiments, the drive comb section may include one to ten micro-robotic arm arrays. The length of the drive comb section opposite the anchor arms 407 can be used as a support 410. Hinges 412 or cantilevers extend through the open space to connect the supports 410 to non-adjacent corners of the frame 402. A sensor bracket 414 is also provided on each support.

[0080] Box 416 generally illustrates the position of the views in Figures 5 through 30B relative to the entire actuator, and the remaining portion of the microelectromechanical system (MEMS) actuator to which the above-described process steps can be applied. The anchor arm portion 132, drive comb portion 134, pivot portion 136, inner frame portion 138, spring portion 140, and outer frame portion 142 of Figure 1 are also shown here. The anchor arm portion 132 is part of the anchor arm 407. The inner frame portion 138, spring portion 140, and outer frame portion 142 constitute part of the actuator frame 402. The overall dimensions of the MEMS actuator are typically in the millimeter range, for example, less than 20 mm x 20 mm.

[0081] Microelectromechanical systems (MEMS) actuators can be used for optical image stabilization (OIS). Optical image stabilization is used to reduce blurring that may occur during exposure due to the movement of imaging devices (such as binoculars, cameras (handheld, stationary, or recording), telescopes, and mobile phones / smartphones). This movement causes light initially detected in one pixel to move to adjacent pixels, thus appearing as blur in the captured image. As pixel size decreases, the blur becomes more noticeable at higher resolutions. In this disclosure, optical image stabilization is performed by moving the image sensor to compensate for changes in the optical path. This is likely better than moving the lens because it reduces the weight and complexity of the lens and provides faster compensation (approximately a few milliseconds instead of tens of milliseconds). MEMS actuators can move on all five axes (i.e., X-axis, Y-axis, roll, yaw, and pitch).

[0082] Figure 33 illustrates a flowchart of a method 440 for stabilizing an optical image against external motion, according to some embodiments. This method is performed using a microelectromechanical system (MEMS) actuator, as shown in Figure 32. Some steps of this method are also illustrated in Figures 34A and 34B.

[0083] First, Figure 34A is a side cross-sectional view of the optical image capturing device 418. As previously described, this device includes a microelectromechanical system (MEMS) actuator 400 located within a housing 420. A sensor connection element 404 is labeled in the figure. Two sensor supports 414 are also shown in the figure, and an image sensor 422 is mounted on the MEMS actuator by means of connection to the sensor supports 414. The image sensor may be, for example, a charge-coupled device (CCD) or an active pixel sensor (CMOS sensor). One or more lenses 424 are present within the housing. The image sensor is located between the lens and the MEMS actuator, so that light can fall on the image sensor. Herein, the image sensor 422 is in a first position, and an optical path exists between the lens 424 and the image sensor 422.

[0084] When the device / housing is subjected to an external force, such as shaking in the user's hand, in step 442 of Figure 33, the microelectromechanical system (MEMS) actuator is moved to compensate for the external force. This can be achieved, for example, by changing the physical distance between the interlaced fingers by sending electrical signals to an array of micromanipulators in one or more quadrants. As shown in Figure 34B, this causes the sensor connection element 404 of the MEMS actuator 400 to tilt relative to the frame, thereby moving the image sensor 422 to a second position while the optical path still illuminates the same position on the image sensor.

[0085] When the structure of a microelectromechanical system includes an array of microrobotic arms with piezoelectric fingers, it becomes more stable and less susceptible to damage. The same result occurs when the ratio of the number of fingers between two finger arrays in the microrobotic arm array is greater than 1. This extends the lifespan of the device and improves customer satisfaction.

[0086] This disclosure provides a method for manufacturing a micromanipulator array for a microelectromechanical system actuator. The method includes the following operations: forming a first finger array on a wafer using a piezoelectric material; forming a second finger array on the wafer using a conductive material, wherein a plurality of distal ends of the first finger array and a plurality of distal ends of the second finger array are interposed between each other to form a plurality of distal ends of adjacent fingers interposed with each other; forming a plurality of microspring precursor structures between the distal ends of adjacent fingers interposed with each other and on each finger in the first finger array; forming a metal cap that contacts each finger in the second finger array and each of the microspring precursor structures on the first finger array; forming a cavity in the wafer below the first and second finger arrays; and performing annealing to convert each of the microspring precursor structures into a microspring.

[0087] This disclosure also provides a method for manufacturing a micro-manipulator array for a microelectromechanical system actuator. The method includes the following operations: receiving a package including a top wafer bonded to a bottom wafer; patterning the top wafer to form a recess, the recess including a plurality of pillars spaced apart from each other within the recess; forming a dielectric layer on a plurality of exposed surfaces of the recess in the top wafer; forming a plurality of metal layers on the pillars in the recess to form a plurality of horizontal composite structures on the pillars; forming a plurality of sacrificial spacers on the horizontal composite structures; forming a dielectric layer on the plurality of exposed surfaces of the horizontal composite structures and the sacrificial spacers, thereby forming a first set of trenches and a second set of trenches within the recess and forming a first dielectric layer on the top wafer; depositing a piezoelectric material into the first set of trenches to form a first finger array; depositing a conductive material into the second set of trenches to form a second finger array, wherein a plurality of distal ends of the first finger array and a plurality of distal ends of the second finger array are interposed between each other. A plurality of vertical composite structures are formed on a plurality of fingers of a first finger array, each of the vertical composite structures including a dielectric layer bonded to a metal layer. A metal cap is formed, the metal cap contacting each finger of a second finger array and each of the vertical composite structures on the first finger array. Etching is performed to remove sacrificial spacers and form cavities within the top wafer. Annealing is performed to transform each of the horizontal composite structures and each of the vertical composite structures into microsprings.

[0088] This disclosure further provides a microelectromechanical system (MEMS) actuator. The MEMS actuator includes an anchor structure and an array of multiple micromanipulators. The micromanipulator arrays are connected to the anchor structure, each of the micromanipulator arrays including a first spacer finger array and a second spacer finger array. The first spacer finger array is formed of a piezoelectric material and extends from a first arm along a first horizontal direction. The second spacer finger array is formed of a conductive material and extends from a second arm along a first horizontal direction, wherein multiple distal ends of the first spacer finger array and multiple distal ends of the second spacer finger array are interposed between each other to form multiple distal ends of adjacent fingers interposed to each other.

[0089] In some embodiments, each of the micromanipulator arrays further includes: a plurality of microsprings connecting the distal ends of adjacent fingers to which they are inserted into each other; metal caps on the distal ends of the first spaced finger array and the second spaced finger array; and a plurality of microsprings connecting the metal caps to the distal ends of the plurality of fingers of the first spaced finger array.

[0090] In some embodiments, the first spaced finger array and the second spaced finger array are located within the drive comb portion, and each of the micromanipulator arrays further includes an anchor arm portion, a pivot portion, an inner frame portion, a spring portion, and an outer frame portion connected to the anchor structure.

[0091] Various embodiments of this disclosure also describe a method for stabilizing an optical image to resist external motion. The method is achieved by moving a microelectromechanical system (MEMS) actuator to compensate for external motion, wherein an image sensor is mounted on the MEMS actuator. The MEMS actuator includes a plurality of micro-robotic arm arrays connected to an anchor structure, and each arm array has elements as described above.

[0092] This disclosure also relates to optical image capturing devices in various embodiments, the optical image capturing device comprising: an image sensor mounted on a microelectromechanical system (MEMS) actuator; and a lens, wherein the image sensor is located between the lens and the MEMS actuator. The MEMS actuator includes a plurality of micromanipulator arrays connected to an anchor structure. Each arm array includes: a first spaced-out finger array formed of a piezoelectric material, the first spaced-out finger array extending from a first arm along a first horizontal direction; and a second spaced-out finger array formed of a conductive material, the second spaced-out finger array extending from a second arm along a first horizontal direction. The distal ends of the first finger array and the distal ends of the second finger array are interposed between each other.

[0093] Some further embodiments of this disclosure also relate to various methods of manufacturing micromanipulator arrays for microelectromechanical system actuators. A first finger array is formed on a wafer. A second finger array is formed on a wafer. The distal ends of the first finger array and the distal ends of the second finger array are interleaved. The ratio of the number of fingers in the first array to the number of fingers in the second array is an integer greater than 1. Microspring precursor structures are formed between the interleaved distal ends of adjacent fingers and on each finger of the first finger array. A metal cap is formed, which contacts each finger in the second finger array and each microspring precursor structure on the first finger array. Next, a cavity is formed in the wafer below the first and second finger arrays. Annealing is performed to convert each microspring precursor structure into a microspring.

[0094] Other embodiments of this disclosure relate to various methods of manufacturing micromanipulator arrays for microelectromechanical system actuators. A package is received, the package including a top wafer bonded to a bottom wafer. The top wafer is patterned to form a recess, the recess including a plurality of pillars spaced apart from each other within the recess. A dielectric layer is formed on the exposed surface of the recess of the top wafer. A metal layer is formed on each pillar in the recess to obtain a horizontal composite structure on each pillar. A sacrificial spacer is formed on each horizontal composite structure. A dielectric layer is formed on the exposed surfaces of the horizontal composite structure and the sacrificial spacer, thereby forming a first set of trenches and a second set of trenches within the recess, and a first dielectric layer is formed on the top wafer. A first array of fingers is formed in the first set of trenches. A second array of fingers is formed in the second set of trenches. The distal ends of the first array of fingers and the distal ends of the second array of fingers are staggered. The ratio of the number of fingers in the first array to the number of fingers in the second array is an integer greater than 1. A vertical composite structure is formed on each finger of the first array of fingers. Each vertical composite structure includes a dielectric layer bonded to a metal layer. A metal cap is formed, which contacts each finger in the second finger array and each vertical composite structure on the first finger array. Etching is performed to remove sacrificial spacers and form cavities within the top wafer. Annealing is then performed to transform each horizontal composite structure and each vertical composite structure into a microspring.

[0095] Various embodiments of this disclosure also describe a microelectromechanical system (MEMS) actuator including an anchor structure. Multiple micromanipulator arrays are connected to the anchor structure. Each arm array includes a first finger array and a second finger array. The first finger array, having spaced-apart fingers, extends from a first arm in a first horizontal direction. The second finger array, having spaced-apart fingers, extends from a second arm in a first horizontal direction. The distal ends of the first finger array and the distal ends of the second finger array are interleaved. The ratio of the number of fingers in the first array to the number of fingers in the second array is an integer greater than 1.

[0096] In a further embodiment of the microelectromechanical system actuator, each arm array further includes: a microspring connecting the distal ends of each group of adjacent fingers inserted therebetween; a metal cap on the distal ends of the first finger array and the second finger array; and a microspring connecting the metal cap to the distal end of each finger of the first finger array.

[0097] Furthermore, the first finger array and the second finger array are located within the drive comb portion. The arm array may also include an anchor arm portion, a pivot portion, an inner frame portion, a spring portion, and an outer frame portion connected to the anchor structure.

[0098] Various embodiments of this disclosure also describe a method for stabilizing optical images to resist external motion. This is achieved by compensating for external motion by moving a microelectromechanical system (MEMS) actuator, wherein an image sensor is mounted on the MEMS actuator. The MEMS actuator includes multiple arrays of microrobotic arms connected to an anchor structure. Each arm array has two arrays of fingers. The ratio of the number of fingers in the first array to the number of fingers in the second array is an integer greater than 1.

[0099] Finally, this disclosure also relates to optical image capturing devices in various embodiments, the optical image capturing device comprising: an image sensor mounted on a microelectromechanical system (MEMS) actuator; and a lens, wherein the image sensor is located between the lens and the MEMS actuator. The MEMS actuator includes a plurality of micromanipulator arrays connected to an anchor structure. Each arm array includes: a first spaced-out finger array extending from a first arm in a first horizontal direction; and a second spaced-out finger array extending from a second arm in the first horizontal direction. The distal ends of the first finger array and the distal ends of the second finger array are interleaved. The ratio of the number of fingers in the first array to the number of fingers in the second array is an integer greater than 1.

[0100] The foregoing has outlined several features of the embodiments to enable those skilled in the art to better understand various aspects of this disclosure. Those skilled in the art should understand that they can readily use this disclosure as a basis for designing or modifying other processes and structures to achieve the same objectives and / or advantages as the embodiments described herein. Those skilled in the art should also recognize that such equivalent architectures do not depart from the spirit and scope of this disclosure, and that various changes, substitutions, and modifications can be made to this document without departing from its spirit and scope. [Simplified Explanation of the Diagram]

[0005] The various aspects of this disclosure can be best understood from the following detailed description when read in conjunction with the drawings. It should be noted that, according to industry standard practice, various features may not be drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or decreased for clarity of discussion. Figure 1 is a side cross-sectional view of a micromechanical arm array according to some embodiments of this disclosure. Figure 2 is an enlarged side cross-sectional view of a micromechanical arm array according to some embodiments of this disclosure. Figure 3A is a plan view of the micromechanical arm array in the first embodiment, which has a first piezoelectric finger array, a second conductive finger array, and microsprings, with the distal ends of the first piezoelectric finger array and the distal ends of the second conductive finger array inserted between each other, and the microsprings connecting adjacent fingers. The ratio of piezoelectric fingers to conductive fingers is 2:1. Figure 3B is a plan view of the micromechanical arm array in the second embodiment, which has a first piezoelectric finger array inserted into the second conductive finger array. The ratio of piezoelectric fingers to conductive fingers is 1:1. Figure 3C is a plan view of the micro-manipulator array in the third embodiment, the micro-manipulator array having a first piezoelectric finger array into which a second conductive finger array is inserted. The ratio of piezoelectric fingers to conductive fingers is 3:1. Figures 4A to 4C are flowcharts of a first method for manufacturing a micro-manipulator array for a microelectromechanical system actuator according to some embodiments. Figure 5 is a side cross-sectional view of a package for manufacturing the micro-manipulator array. Figure 6A is a plan view of the package after performing the first etching step. Figure 6B is a side cross-sectional view of the package in Figure 6A along line BB. Figure 6C is a side cross-sectional view of the package in Figure 6A along line CC. Figure 6D is a side cross-sectional view of the package in Figure 6A along line DD. Figure 7 is a side cross-sectional view of the package after forming the first dielectric layer. Figure 8 is a side cross-sectional view of the package after metal deposition. Figure 9A is a side cross-sectional view of the package after etching to form a metal layer on the pillars. Figure 9B is a plan view. Figure 10 is a side cross-sectional view of the package after silicon deposition. Figure 11A is a side cross-sectional view of the package after etching to form sacrificial spacers on the pillars. Figure 11B is a plan view. Figure 12 is a side cross-sectional view of the package after adding a first dielectric layer to the newly exposed surface. Figure 13A is a side cross-sectional view of the package after depositing piezoelectric material to form a first piezoelectric finger array. Figure 13B is a plan view. Figure 14 is a side cross-sectional view of the package after depositing conductive material on the top wafer to form a second conductive finger array.Figure 15A is a side cross-sectional view of the package after chemical mechanical planarization (CMP) is performed on the conductive material. Figure 15B is a plan view. Figure 16 is a side cross-sectional view of the package after etching to remove the conductive material from the trench. Figure 17 is a side cross-sectional view of the package after a first dielectric layer is further added on the two finger arrays. Figure 18 is a side cross-sectional view of the package after partial etching of the first dielectric layer to expose a portion of the top wafer. Figure 19 is a side cross-sectional view of the package after depositing a first etch stop layer on the top wafer. Figure 20 is a side cross-sectional view of the package after forming a second dielectric layer. Figure 21A is a side cross-sectional view of the package after partially etching the second dielectric layer. Figure 21B is a plan view. Figure 22 is a side cross-sectional view of the package after depositing a second etch stop layer on the top wafer. Figure 23A is a side cross-sectional view of the package after etching the etch stop layer to expose multiple portions of the top wafer. Figure 23B is a plan view. Figure 24 is a side cross-sectional view of the package after the deposition of the third dielectric layer. Figure 25A is a side cross-sectional view of the package after etching the third dielectric layer to form a vertical dielectric layer on the first piezoelectric finger array. Figure 25B is a plan view. Figure 26 is a side cross-sectional view of the package after metal deposition. Figure 27A is a side cross-sectional view of the package after etching to form a metal cap. Figure 27B is a plan view. Figure 28A is a side cross-sectional view of the package after the formation of a passivation layer. Figure 28B is a plan view. Figure 29A is a side cross-sectional view of the package after silicon etching of the top wafer to form the cavity under the micro-robotic arm array. Figure 29B is a plan view. Figure 30A is a side cross-sectional view of the package after annealing and removal of the bottom wafer, leaving the top wafer. Figure 30B is a plan view. Figure 31A is a flowchart of a second method for manufacturing a micro-manipulator array for a microelectromechanical system actuator according to some embodiments. Figure 31B is a flowchart of a third method for manufacturing a micro-manipulator array for a microelectromechanical system actuator according to some embodiments. Figure 32 is a plan view of a microelectromechanical system actuator according to some embodiments. Figure 33 is a flowchart of a method for stabilizing an optical image against external motion according to some embodiments. Figure 34A is a side cross-sectional view of an optical image capturing device in a first position. Figure 34B is a side cross-sectional view of the device in a second position. [Biomaterial Storage]

[0102] Domestic storage information (please note in order of storage institution, date, and number): None. International storage information (please note in order of storage country, institution, date, and number): None.

Claims

1. A method for manufacturing a micro-robotic arm array for use as an actuator in a microelectromechanical system, comprising: A first finger array is formed on a wafer using a piezoelectric material; A second finger array is formed on the wafer using a conductive material, wherein a plurality of distal ends of the first finger array and a plurality of distal ends of the second finger array are interposed between each other to form a plurality of distal ends of adjacent fingers interposed with each other; a plurality of microspring precursor structures are formed between the distal ends of the adjacent fingers interposed with each other and on each finger in the first finger array; a metal cap is formed that contacts each finger in the second finger array and each of the microspring precursor structures on the first finger array; a cavity is formed in the wafer below the first finger array and the second finger array; and annealing is performed to convert each of the microspring precursor structures into a microspring.

2. The method as described in claim 1, wherein a height of a plurality of fingers in the second finger array is greater than a height of a plurality of fingers in the first finger array.

3. The method as described in claim 1, wherein each finger in the first finger array and each finger in the second finger array are covered by a covering layer.

4. The method as described in claim 1, wherein each of the micro-spring precursor structures includes a metal layer and a dielectric layer bonded together.

5. The method of claim 1, wherein each of the microspring precursor structures between the distal ends of the adjacent fingers interlocked with each other is formed by: patterning the wafer to form a groove including a plurality of pillars spaced apart from each other within the groove; forming a dielectric layer on each of the pillars; and forming a metal layer on each of the pillars to obtain each of the microspring precursor structures between the distal ends of the adjacent fingers interlocked with each other.

6. The method of claim 1, wherein each of the micro-spring precursor structures on each finger of the first finger array is formed by: depositing a first etch stop layer on the wafer; depositing a second etch stop layer on the wafer; patterning the first etch stop layer and the second etch stop layer to form a plurality of trenches on the distal ends of the first finger array; forming a vertical dielectric layer in each of the trenches; and depositing a metal layer formed as a vertical metal layer in each of the trenches to obtain each of the micro-spring precursor structures on each finger of the first finger array.

7. A method for manufacturing a micro-robotic arm array for use as an actuator in a microelectromechanical system, comprising: Receive a package comprising a top wafer bonded to a bottom wafer; The top wafer is patterned to form a groove, the groove including a plurality of pillars spaced apart from each other within the groove; a dielectric layer is formed on a plurality of exposed surfaces of the groove in the top wafer; a plurality of metal layers are formed on the pillars in the groove to form a plurality of horizontal composite structures on the pillars; a plurality of sacrificial spacers are formed on the horizontal composite structures; a dielectric layer is formed on the plurality of exposed surfaces of the horizontal composite structures and the sacrificial spacers, thereby forming a first set of trenches and a second set of trenches within the groove and forming a first dielectric layer on the top wafer; a piezoelectric material is deposited into the first set of trenches to form a first finger array; a conductive material is deposited into the second set of trenches to form a second finger array, wherein a plurality of distal ends of the first finger array and a plurality of distal ends of the second finger array are interposed between each other; A plurality of vertical composite structures are formed on a plurality of fingers of the first finger array, each of the vertical composite structures including a dielectric layer bonded to a metal layer; a metal cap is formed that contacts each finger of the second finger array and each of the vertical composite structures on the first finger array; etching is performed to remove the sacrificial spacers and form a cavity within the top wafer; and annealing is performed to convert each of the horizontal composite structures and each of the vertical composite structures into a microspring.

8. The method as described in claim 7, wherein a plurality of proximal ends of the first finger array extend in a first direction and are connected to a first arm, and a plurality of proximal ends of the second finger array extend in a second direction opposite to the first direction and are connected to a second arm.

9. The method of claim 7, further comprising, after depositing the conductive material into the second set of trenches to form the second finger array and before forming the vertical composite structures on the fingers of the first finger array: extending the first dielectric layer to a plurality of top surfaces of the first finger array and the second finger array; exposing the top wafer in the drive comb portion by removing a plurality of portions of the first dielectric layer on the top wafer in the drive comb portion; depositing a first etch stop layer on the top wafer; forming a second dielectric layer on the first etch stop layer; patterning the second dielectric layer to expose a portion of the drive comb portion, a hub portion, and an inner frame portion of the top wafer; depositing a second etch stop layer on the top wafer; and patterning the first etch stop layer and the second etch stop layer in the drive comb portion to form a plurality of vertical spacers and to form a plurality of trenches at the distal ends of the first finger array.

10. A microelectromechanical system actuator, comprising: One-anchor structure; And a plurality of micro-robotic arm arrays are connected to the anchor structure, each of the micro-robotic arm arrays including: a first spaced finger array formed of a piezoelectric material, the first spaced finger array extending from a first arm along a first horizontal direction; And a second spacer array formed of a conductive material, the second spacer array extending from a second arm along the first horizontal direction, wherein a plurality of distal ends of the first spacer array and a plurality of distal ends of the second spacer array are inserted between each other to form a plurality of distal ends of adjacent fingers inserted between each other.

Images