Devices including arm array and method of making arm array

Abstract

Microelectromechanical systems (MEMS) structures can be used as actuators for optical image stabilization. MEMS actuators comprise one or more arrays of microrobotic arms. Each arm array includes a first array of spaced-apart fingers and a second array of spaced-apart fingers, the fingers being formed of a conductive material. The fingers of the first array are offset from the fingers of the second array. The distal ends of the first and second finger arrays are separated from each other by lateral grooves. Microsprings connect the distal ends of the fingers in the first array to the distal ends of the fingers in the second array. A metal cap may be present on one or both finger arrays. Rivets may extend from the metal cap to the fingers themselves. The resulting structure increases stability and strength.

Description

Technical Field

[0001] none Prior Technology

[0002] Micro-electromechanical systems (MEMS) are a technology that employs miniature mechanical and electromechanical components (such as 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] MEMS structures can be fabricated using a photolithography process, which uses ultraviolet light to transfer the desired photomask 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 is repeated multiple times using different patterns to create different layers on the wafer substrate and fabricate useful devices. Summary of the Invention

[0004] none Simple Explanation of the Diagram

[0005] The nature of this disclosure can be best understood by reading the following detailed description in conjunction with the accompanying drawings. It should be emphasized that, according to standard industry practice, the various features are not drawn to scale. In fact, for clarity of explanation, the dimensions of the various features may be arbitrarily increased or decreased. Figure 1 is a schematic Y-axis side cross-sectional view of a micromanipulator array according to some embodiments of the present disclosure. Figure 2A is a plan view of a micromanipulator array, showing two arrays of fingers, with microsprings connecting adjacent offset fingers between the two arrays, and microsprings connecting adjacent fingers in the same array, and showing metal caps / strips between them, each finger may have 2 to 4 microsprings. Figure 2B is a plan view of the micro-robotic arm array in Figure 2A, showing another aspect. Figure 3A shows an X-axis side cross-section of two fingers in different arrays, revealing another aspect. Figure 3B is a Y-axis side cross-section of two adjacent fingers in the same array, showing another aspect where the microspring is in the "high" position. Figure 3C is a Y-axis sectional view of another embodiment of two adjacent fingers in the same array, showing another orientation where the microspring is in the "middle" position. Figure 3D is a Y-axis sectional view of a third embodiment of two adjacent fingers in the same array according to some embodiments of this disclosure, showing another aspect where the microspring is in the "low" position. Figure 4A is a Y-axis side cross-sectional view of an alternative embodiment of two adjacent fingers in the same array, where the metal cover is "riveted" to the fingers. Figure 4B is a plan view of a micromanipulator array with fingers as shown in Figure 4A, illustrating a first embodiment in which two finger arrays are separated and offset, with microsprings connecting adjacent offset fingers between the two arrays. Figure 4C is a plan view of the micromanipulator array with finger-like elements of Figure 4A, showing a second embodiment in which the distal ends of two finger-like arrays are inserted between each other, and microsprings may also be present. Figures 5A to 5C illustrate flowcharts of a first method for manufacturing a micro-manipulator array for MEMS actuators according to one embodiment of this disclosure. Figure 6 shows a Y-axis cross-sectional view of the package used to manufacture the micro-robotic arm array. Figure 7A is a plan view of the package after the first etching step; Figure 7B is a Y-axis cross-sectional view of the package taken along line BB in Figure 7A; Figure 7C is a Y-axis cross-sectional view of the package taken along line CC in Figure 7A. Figure 8A is a plan view of the package after the second etching step. Figure 8B is a Y-axis cross-sectional view of the package taken along line BB of Figure 8A after the second etching step. Figure 8C is a Y-axis cross-sectional view of the package taken along line CC of Figure 8A. Figure 9A is a Y-axis cross-sectional view of the package taken along line BB of Figure 8A after the formation of the first dielectric layer. Figure 9B is a Y-axis cross-sectional view of the package taken along line CC of Figure 8A. Figure 10A is a Y-axis cross-sectional view of the package taken along line BB of Figure 8A after metal deposition. Figure 10B is a Y-axis cross-sectional view of the package taken along line CC of Figure 8A. Figure 11A is a plan view of the package after etching to form a metal layer on the pillars. Figure 11B is a Y-axis cross-sectional view of the package taken along line BB of Figure 11A. Figure 11C is a Y-axis cross-sectional view of the package taken along line CC of Figure 11A. Figure 12A is a Y-axis cross-sectional view of the package along line CC of Figure 11A after silicon deposition into the lateral trenches and the extension of the first dielectric layer. Figure 12B is a Y-axis cross-sectional view of the package along line BB of Figure 11A, and shows the optional etching to form sacrificial spacers on the pillars. Figure 12C is a Y-axis cross-sectional view of the package along line BB of Figure 11A, and shows the optional addition of the first dielectric layer on the exposed surface. Figure 13 is a Y-axis cross-sectional view of the package along line BB in Figure 11A after the deposition of conductive material to form the first and second finger arrays. Figure 14 is a Y-axis cross-sectional view of the package along line BB in Figure 11A after the CMP of the conductive material. Figure 15 is a Y-axis cross-section of the package along line BB in Figure 11A after the first dielectric layer is added above the two finger arrays. Figure 16A is a plan view of the package after the first dielectric layer has been partially etched to expose a portion of the top wafer. Figure 16B is a Y-axis cross-sectional view of the package taken along line BB of Figure 16A. Figure 17 is a Y-axis cross-section of the package along line BB in Figure 16A after the first etch stop layer has been deposited above the top wafer. Figure 18 is a cross-sectional view of the package along line BB in Figure 16A after the formation of the second dielectric layer. Figure 19A is a plan view of the package after the second dielectric layer has been partially etched. Figure 19B is a Y-axis cross-sectional view of the package taken along line BB in Figure 19A. Figure 20 is a Y-axis cross-section of the package along line BB in Figure 19A after a second etch stop layer has been deposited above the top wafer. Figure 21A is a plan view of the package after the etch stop layer has been etched to expose the various portions of the top wafer. Figure 21B is a Y-axis cross-sectional view of the package taken along line BB of Figure 21A. Figure 22A is a plan view of the package after optional etching to form openings in the fingers for subsequent rivet formation. Figure 22B is a Y-axis cross-sectional view of the package taken along line BB of Figure 22A. Figure 23A is a Y-axis cross-sectional view of the package along line BB of Figure 22A after metal deposition. Figure 23B is a Y-axis cross-sectional view of the package after metal deposition if optional etching is performed to form openings in the fingers, showing the formation of the rivets. Figure 24A is a plan view of the package after optional etching to form openings in the fingers and etching to form a metal cap over each array of fingers. Figure 24B is a Y-axis cross-sectional view of the package taken along line BB of Figure 24A. Figure 25A is a plan view of the package after the passivation layer has been formed and optionally etched to form openings in the fingers. Figure 25B is a Y-axis cross-sectional view of the package taken along line BB of Figure 25A. Figure 26 is a Y-axis cross-sectional view of the package along line BB in Figure 25A after partial silicon etching through the etch stop layer and the top wafer. Figure 27A is a plan view of the package after the top wafer has been fully silicon etched to form a cavity below the micro-robotic arm array. Figure 27B is a Y-axis cross-sectional view along line BB in Figure 27A. Figure 27C is a Y-axis cross-sectional view along line CC in Figure 27A. Figure 28A is a plan view of the package after annealing and removal of the bottom wafer, leaving the top wafer. Figure 28B is a cross-sectional view along line BB in Figure 28A along the Y-axis. Figure 29 is a flowchart illustrating a second method for manufacturing a micromanipulator array for MEMS actuators according to some embodiments of this disclosure. Figure 30 is a flowchart illustrating a third method for manufacturing a micromanipulator array for MEMS actuators according to some embodiments of this disclosure. Figure 31 is a plan view illustrating a MEMS actuator according to some embodiments of this disclosure. Figure 32 is a flowchart illustrating a method for stabilizing optical images to resist external movement according to some embodiments of the present disclosure. Figure 33A is a side cross-sectional view of the optical image capturing device in the first position. Figure 33B is a side cross-sectional view of the device in the second position. Implementation

[0006] The following disclosure provides numerous different embodiments or instances of various features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the embodiments of this disclosure. Of course, these examples are merely exemplary 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 an additional feature may be formed between the first and second features so that the first and second features are not in direct contact. Furthermore, reference numerals and / or letters may be repeated in different instances of the embodiments of this disclosure. This repetition is for simplicity and clarity and does not in itself establish a relationship between the various embodiments and / or configurations discussed.

[0007] Furthermore, spatial relative terms, such as "below," "below," "lower," "above," "upper," and similar terms, may be used herein for ease of description to describe the relationship of one element or feature relative to another element or feature, as illustrated in the accompanying drawings. Spatial relative terms are intended to cover different orientations of the apparatus in use or operation other than those described in the accompanying drawings. The apparatus may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptive terms used herein shall be understood accordingly.

[0008] The numerical values ​​in the specification and claims of this application should be understood to include the same numerical value when reduced to the same number of significant figures, and the numerical value that differs from the stated value by less than the conventional experimental error of the measurement technique of the type described in the application, in order to determine the value. All ranges disclosed herein include the endpoints described.

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

[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), it simply means 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 of a structure can be considered to be "on" the substrate, even if they are not all in direct contact with the substrate. The term "direct" can be used to mean that two layers are in direct contact with each other without any layer between them. Additionally, when referring to processing steps performed on a substrate or on a substrate, this should be understood as performing these steps on any layers that may be present on the substrate, depending on the context.

[0011] This disclosure refers to "arrays" or "sets" of components. An array or set contains at least one component and cannot contain zero components. These terms should not be construed as requiring at least two components.

[0012] This disclosure relates to arm arrays that can be used in a variety of devices and are particularly suitable for use in microelectromechanical systems (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 function as stand-alone handheld cameras or as part of devices like mobile phones. However, micro-robotic arm arrays can be damaged by impacts / collisions, such as drops from heights.

[0013] This disclosure presents a novel arm array with improved stability and strength. The arm array includes two finger arrays, each extending from an arm. In some embodiments, the fingers of the two arrays extend toward each other, are offset from each other, and are spaced apart from each other by transverse grooves. Micro-springs are present, extending through the transverse grooves from each finger of one array to one or more fingers of the other array. Micro-springs may also be present between adjacent fingers in the same array. In some additional embodiments, a metal cap is present above the finger array. The metal cap above the finger array includes rivets extending to the fingers. These structures improve the lifespan, stability, and strength of the springs.

[0014] Figure 1 is a side cross-sectional view of a first exemplary embodiment of a package 100 including an arm array 148 according to some embodiments of the present disclosure.

[0015] Package 100 includes a top wafer 110 (also called a device wafer) and a bottom wafer 120 (also called a carrier wafer), which are bonded together through a bonding layer 130. This package is also known as a silicon-on-insulator (SOI) substrate.

[0016] Next, a micro-robotic arm array 148 exists within the top wafer 110. The top wafer 110 has multiple cross-sections in the horizontal direction, here 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-robotic arm array 148 is located within the drive comb portion 134. These different portions collectively constitute the quadrant of the MEMS actuator (as will be discussed later herein).

[0017] The anchor arm portion 132 provides structural integrity and helps support the drive comb portion. The hinge portion 136 allows pivoting motion, or controlled rotation of other components relative to the drive comb portion. The inner frame portion 138 provides structural support and stability. The spring portion 140 provides a degree of elasticity to maintain the desired positioning and movement of the components, and also provides a restoring force to return the components to their original position after actuation. The outer frame portion 142 generally provides structural integrity, protecting the internal components from external and environmental forces.

[0018] 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. This cavity also extends continuously below the hinge portion 136, the inner frame portion 138, and the spring portion 140. Two smaller cavities 122 also exist within the bottom wafer 120, typically located below the hinge portion 136, the inner frame portion 138, and the spring portion 140. The cavity 112 in the top wafer 110 connects to the two smaller cavities 122 in the bottom wafer 120.

[0019] The micromanipulator array comprises two separate arrays of fingers: an array of first fingers 150 and an array of second fingers 170 (not visible here), which may also be referred to herein as a first array of multiple fingers and a second array of multiple fingers. Note that there may be more than one first array of multiple fingers and more than one second array of multiple fingers.

[0020] Figure 2A is a plan view of the micro-robotic arm array in Figure 1. Again, this is a highly simplified illustration provided for illustrative purposes only and does not fully represent the complete micro-robotic arm array 148.

[0021] Here, the array of first fingers 150 and the array of second fingers 170 can be better seen. The first fingers 150 extend along a first direction 214 and connect to a first arm 168. In other words, the first fingers 150 extend from the first arm. The first arm is also made of the same conductive material as the first fingers. The second fingers 170 extend along a second direction 216 opposite to the first direction and connect to a second arm 188. In other words, the second fingers 170 extend from the second arm. The second arm is also made of the same conductive material as the second fingers. The first fingers 150 and the second fingers 170 extend along a first horizontal direction (i.e., the X-axis or longitudinal direction). The first arm 168 and the second arm 188 extend in a second horizontal direction (i.e., the Y-axis or transverse direction). Although not shown here, the other ends of the two arms connect to the anchor arm portion 132 and the outer frame portion 142. Metal caps 196 above some of the first fingers 150 are also visible here. Metal caps 197 are also present above some of the second fingers 170.

[0022] Figure 2B is a schematic enlarged plan view of the micromanipulator array of Figure 2A, showing another aspect. First, a first finger 150 and a second finger 170 are shown. The proximal end 162 of the first finger is connected to the first arm 168, and the distal end 160 extends away from the first arm along a first direction 214. Similarly, the proximal end 182 of the second finger is connected to the second arm 188, and the distal end 180 extends away from the second arm along a second direction 216. The first finger 150 can be described as extending from the first arm 168 toward the second finger 170, and vice versa. In some embodiments, the first finger 150 and the second finger 170 may independently have lengths 167, 187 from about 1 millimeter (mm) to about 3 millimeters (mm), but other values ​​and ranges are also within the scope of this disclosure.

[0023] The first fingers 150 are laterally spaced apart from each other. Similarly, the second fingers 170 are laterally spaced apart from each other. The first fingers 150 and the second fingers 170 are laterally offset. In this plan view, the offset is reflected in the fact that the first fingers 150 and the second fingers 170 are not aligned with each other in the first direction 214 and the second direction 216. For example, if the first fingers 150 and the second fingers 170 move toward each other along the first direction or the second direction, their distal ends will not touch each other, but will instead interlock or stagger.

[0024] A given finger within a given array may have one or two adjacent fingers within that array, depending on the position of the given finger. For example, a first finger 190 may have an adjacent first finger 191 on one side and an adjacent first finger 192 on the other side. A given finger within a given array may also have one or two adjacent fingers on another array. Those adjacent fingers on the other array are the fingers closest to the given finger. For example, a first finger 190 may have an adjacent second finger 193 on one side and an adjacent second finger 194 on the other side. The distal end 160 of the first finger 150 does not overlap horizontally or vertically with the distal end 180 of the second finger 170. A transverse groove 234 is located between the arrays of the two fingers 150 and 170.

[0025] For a given finger in one array, a longitudinal microspring 202 connects the finger to an adjacent finger in another array. For example, a first finger 190 is connected to an adjacent second finger 193, 194 via the longitudinal microspring 202. The longitudinal microspring is typically connected between the distal ends of the first and second fingers.

[0026] Lateral microsprings 204 connect the ends of adjacent fingers within a given array of fingers. For example, a first finger 190 is connected to adjacent first fingers 191 and 192 via lateral microsprings 204. Lateral microsprings are also typically connected to the distal ends of the first and second fingers as well. The combination of longitudinal microsprings 202 and lateral microsprings 204 creates a structure that appears very much like a mesh. It should be noted that the longitudinal microsprings 202 and lateral microsprings 204 are shown here with curved structures only for the purpose of distinguishing them from other features. In a physical device, they can be in a relatively straight form.

[0027] Individual metal caps 196 and 197 are also present on each array of fingers. It is worth noting that the metal caps do not need to cover all of the first or second fingers. Furthermore, the metal caps do not need to be aligned with each other, although they can be.

[0028] Figure 3A is an enlarged X-axis side sectional view of the first finger 150 and the second finger 170, showing another aspect. As shown here, the distal ends 160, 180 of the first finger 150 and the second finger 170 are connected to each other via longitudinal microsprings 202.

[0029] The microspring is made of a combination of two layers: a metal layer 206 and a dielectric layer 208. In a particular embodiment, the metal layer 206 is a metal or metal alloy, such as, but not limited to, aluminum (Al) or aluminum alloys, such as AlCu or AlSiCu; copper (Cu); tungsten (W); or nickel (Ni). In a particular embodiment, the dielectric layer is made of silicon dioxide (SiO2), but 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 reduces the energy transferred to the fingers due to external impacts. The angle formed between the microspring 202 and either finger 150, 170 is typically close to 90°. In some embodiments, each layer 206, 208 may have a height of about 0.5 µm.

[0030] The longitudinal microspring 202 has a length 203. In some specific embodiments, the length 203 can be from about 3 micrometers (µm) to about 6 µm. Other ranges are also within the scope of this disclosure. Metal caps 196 and 197 are also shown.

[0031] Each first finger has a free end 156 (or bottom end) and a fixed end 158 (or top end). Each second finger also has a free end 176 and a fixed end 178. The height of the first finger is 163. The height of the second finger is 183. As shown here, the heights 163 and 183 of the two fingers are approximately the same. In some specific embodiments, the heights 163 and 183 may independently range from about 150 micrometers (µm) to about 200 µm. Other ranges are also within the scope of this disclosure. Additionally, the first finger 150 and the second finger 170 are shown positioned such that their top surfaces are at the same height or level. Again, this is not necessary for the operation of the microrobotic arm array.

[0032] Figure 3B is an enlarged Y-axis cross-sectional view of the micro-robotic arm array 148. Note that this is a highly simplified illustration for descriptive purposes only and does not fully represent the complete micro-robotic arm array. It should be noted that the following discussion refers only to the first finger 150, but the same applies to the second finger 170.

[0033] As shown here, each first finger 150 includes a core 152 formed of a conductive 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. In a particular embodiment, the first finger 150 and the second finger 170 are made of polycrystalline silicon, and the capping layer is formed of silicon dioxide (SiO2).

[0034] In this view, the width of the first finger is 165. In some specific embodiments, the width 165 may independently range from about 1 micrometer (µm) to about 4 µm. Other ranges are also within the scope of this disclosure.

[0035] Lateral microsprings 204 are present between adjacent first fingers 150, and the description of the longitudinal microsprings above also applies to them. In some specific embodiments, their width 205 can be from about 3 micrometers (µm) to about 6 µm. This is also an approximation of the distance between adjacent fingers in the same finger array. Other ranges are also within the scope of this disclosure. It should be noted that the distance between adjacent fingers is generally approximately the same for both the array of first fingers and the array of second fingers. The angle formed between the lateral microsprings 204 and any of the first fingers 150 is generally close to 90°.

[0036] It is noteworthy that the metal layer 206 of the transverse microspring 204 passes through the cover layer 154 and contacts the core 152. In a particular embodiment, the thickness 155 of the cover layer corresponding to the overlapping metal layer is approximately 0.3 micrometers (µm) to approximately 0.5 µm. It has also been found that the stability of the spring increases when there is a minimum distance 195 of approximately 4 µm between the metal cap 196 and the longitudinal microspring 202 and the transverse microspring 204. Other ranges are also within the scope of this disclosure.

[0037] A passivation layer 201 is present on the top surface 198 of the metal cap. As shown here, the metal cap 196 directly contacts the fixed end 158 of the array of first fingers 150. The free ends 156, 176 of the two finger arrays are free to move under the metal cap. The metal cap can be described as having a lower portion that directly contacts the first fingers and an upper portion that spans the distance between adjacent fingers. The width 199 of the upper portion of the metal cap is generally greater than the width 205 of the transverse microspring. In some specific embodiments, the width 199 of each upper portion of the metal cap is about 3µm to about 6µm, but other ranges are also within the scope of this disclosure. The width 200 of the lower portion of the metal cap is generally greater than the width 165 of the first fingers 150. In some specific embodiments, the width 200 of the lower portion of the metal cap is about 2µm to about 5µm, but other ranges are also within the scope of this disclosure. Note that the upper and lower portions of the metal cap overlap each other. It should also be noted that the metal cap is not rigid and is only used to keep the fingers apart.

[0038] Figure 3C is an enlarged Y-axis cross-sectional view of a second embodiment of the arm array 148. Figure 3D is an enlarged Y-axis cross-sectional view of a third embodiment of the arm array 148. The difference between these figures lies in the position of the lateral microspring 204. In Figure 3B, the lateral microspring 204 is in a "high" position relative to the first finger 150, closest to the metal cap and within the upper 1 / 3 of the height of the first finger, near the fixed end 158. In Figure 3C, the lateral microspring 204 is in a "middle" position relative to the first finger 150, within the middle 1 / 3 of the height of the first finger. In Figure 3D, the lateral microspring 204 is in a "low" position relative to the first finger 150, furthest from the metal cap and within the lower 1 / 3 of the height of the first finger, near the free end 156.

[0039] Figure 4A is a plan view of an alternative embodiment of the arm array 148. Here, there are rivets 280 extending from the metal cap 196 into the core 152 of the first finger 150. The rivets are made of the same material as the metal cap 196. In the embodiment shown here, each rivet 280 has an upper width 281 and a lower width 283. In some specific embodiments, the upper width 281 may be greater than the lower width 283. For example, the upper width 281 may be about 2µm to about 4µm, and the lower width 283 may be about 1µm to about 3µm. In other embodiments, the upper width 281 and the lower width 283 are approximately equal to each other, and in some examples are about 1µm to about 4µm. In some embodiments, the rivets may have a height 285 of about 3µm to about 10µm, at least 4µm. However, other ranges are also within the scope of this disclosure.

[0040] Figure 4B is a plan view of one possible embodiment of the arm array 148 in Figure 4A. This embodiment is similar to the embodiment previously shown in Figure 2B, wherein the distal end 160 of the first finger 150 does not overlap horizontally or vertically with the distal end 180 of the second finger 170. A transverse groove 234 is located between the arrays of the two fingers 150, 170. A longitudinal microspring 202 and a transverse microspring 204 are present. As shown, a rivet 280 is present within the first finger 150 and the second finger 170, located below the corresponding metal caps 196, 197 (shown in dashed lines). Variations where the rivet 280 is present only in the first finger or only in the second finger are also within the scope of this disclosure.

[0041] Figure 4C is a plan view of another possible embodiment of the arm array 148 in Figure 4A. Rivets 280 are present again. Here, the distal end 160 of the first finger 150 may horizontally overlap with the distal end 180 of the second finger 170, or in other words, they may be inserted into or staggered. Longitudinal microsprings 202 may exist between fingers in different arrays, and transverse microsprings 204 may exist between adjacent fingers in the same array. In this embodiment, the first finger 150 and the second finger 170 may be covered by a common metal cap 196, shown in dashed lines. Similarly, variations where rivets 280 are present only in the first finger or only in the second finger are also within the scope of this disclosure.

[0042] Figures 5A through 5C together are flowcharts illustrating a first method 300 for manufacturing an arm array according to some embodiments. The arm array can be a micro-robotic arm array and can be used in various devices, such as MEMS devices. Some steps of this method are also shown in Figures 6 through 28B. These figures provide different perspectives for better understanding. Although the method steps are discussed below based on the formation of a single micro-robotic arm array with a small number of fingers, such a discussion should also be interpreted broadly as applicable to the simultaneous formation of multiple micro-robotic arm arrays located in a single drive comb portion, and it is also possible to form an array of many fingers. These figures do not show the formation of the entire actuator, only the drive comb portion. In addition, methods using only some of the steps shown in the flowcharts are considered to fall within the scope of this disclosure.

[0043] First, in step 302 of Figure 5A and as shown in Figure 6, the top wafer 110 is bonded to the bottom wafer 120 to form package 100. Alternatively, as shown in step 304 of Figure 5A, the package is received.

[0044] 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, such as silicon in crystalline form Si. In 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 rhodium phosphide. In a particular embodiment, both wafers are made of silicon.

[0045] The top wafer includes a top surface 114 that also serves as the top surface of the package. Generally, the top wafer 110 has a relatively low thickness 115 (e.g., in the range of about 200 µm), which makes it very flexible and therefore difficult to process individually. The bottom wafer 120 has a relatively high thickness 125 (e.g., in the range of about 500 µm), which increases the overall thickness of the package and thus provides mechanical stability during processing, and can also contribute to electrical isolation (if desired). Two cavities 122 are already present within the bottom wafer 120. The bonding layer 130 can be formed by fusion, for example, through a heating and / or pressing process without any additional layers. As another example, both wafers can have dielectric layers on appropriate surfaces, and then the dielectric layers are heated. The two wafers are then pressed together to form the bonding layer.

[0046] Next, in step 306 of Figure 5A and as shown in Figures 7A to 7C, the top wafer 110 is patterned to form multiple structures. These include a set of first longitudinal trenches 230, a set of second longitudinal trenches 232, and lateral trenches 234. One or more longitudinal pillars 222 are formed within the lateral trenches. The two sets of trenches 230, 232 will correspond to two different finger arrays. A region 236 exists between the two sets of trenches. As shown, the longitudinal pillars 222 connect the first trenches 230 to the second trenches 232. The first trenches 230, second trenches 232, and lateral trenches 234 are 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 at positions corresponding to the hinge portion 136, the inner frame portion 138, and the outer frame portion 142. The longitudinal pillars correspond to positions where longitudinal microsprings will be formed. The resulting structure is shown in Figures 7A to 7C.

[0047] Figure 7B is a side cross-sectional view of the package taken along line BB of Figure 7A. This cross-section passes through the location where the lateral microsprings will be formed. In this cross-section, only the trench 230 for the first finger is visible. Figure 7C is a side cross-sectional view of the package taken along line CC of Figure 7A. This cross-section passes through the location where the longitudinal microsprings will be formed. The trenches 230, 232 for the first and second fingers are not visible. Note that the additional trenches 137, 139, 143 are also not visible here and do not pass through this portion of the top wafer.

[0048] Next, in step 308 of Figure 5A, the vertical pillars 222 are patterned to the desired height. In an optional step 310 of Figure 5A, if desired, the horizontal pillars 224 are patterned into the top wafer to the desired height. The resulting structure is shown in Figures 8A through 8C.

[0049] Figure 8A is a plan view of the package after these two patterning / etching steps. The different depths of trenches 230 and 232, as well as the longitudinal pillars 222 and the transverse pillars 224, are indicated by different shading. Figures 8B and 8C show that the longitudinal pillars 222 and the transverse pillars 224 can be patterned to have different heights from each other if desired. However, it can be expected that if they have the same height, only one patterning / etching operation is required.

[0050] Next, in step 312 of Figure 5A and as shown in Figures 9A and 9B, a first dielectric layer 240 is formed on the exposed surfaces of trenches 230, 232 and pillars 222, 224. The first dielectric layer is also formed on other exposed surfaces of the top wafer 110, including top surface 114. In a particular embodiment, the material of the first dielectric layer is silicon dioxide (SiO2), which can be formed by thermal oxidation of a silicon wafer. Of particular note is that the portion of the first dielectric layer 240 on pillars 222, 224 will form a dielectric layer 208 for microsprings.

[0051] Next, in step 314 of Figure 5A and as shown in Figures 10A and 10B, metal 242 is deposited over the top wafer. Then, in step 316 of Figure 5A and as shown in Figures 11A to 11C, the metal is patterned to form a metal layer 206 on each pillar 222, 224. This metal layer will form the metal layer of the microspring. In a particular embodiment, the metal is aluminum (Al) or an aluminum alloy, such as AlCu or AlSiCu. For example, the metal can be deposited by evaporation or sputtering, electroplating, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), or other suitable methods. As can be better seen in Figures 11B and 11C, the metal layer 206 is present only on the pillars 222, 224 and not in the trenches 230, 232, 234 within the recesses. The combination of dielectric layer 208 and metal layer 206 on each pillar is also referred to herein as a microspring precursor structure or a horizontal composite structure. A transverse microspring precursor structure 212 is seen in Figure 11B, and a longitudinal microspring precursor structure 210 is seen in Figure 11C. Note that these microspring precursor structures 210, 212 are shown formed at different heights from each other, with the transverse microspring precursor structure 212 higher than the longitudinal microspring precursor structure 210.

[0052] Continuing, in step 318 of Figure 5A and as shown in Figure 12A, sacrificial material 244 is deposited on the top wafer, including within the lateral trench 234. The sacrificial material can be deposited using CVD, PVD, or other suitable methods. In a particular embodiment, the sacrificial material is the same material as the top wafer, such as silicon. If the lateral pillars 224 are placed at a different height than the longitudinal pillars, the sacrificial material can also be patterned in optional step 320 of Figure 5A and as shown in Figure 12B to form sacrificial spacers 246 on the lateral pillars 224.

[0053] In step 322 of Figure 5A and as shown in Figures 12A and 12C, a dielectric layer is formed on the exposed surfaces of the metal layer 206 and the sacrificial material and sacrificial spacers 246. This step can be considered as adding to the first dielectric layer 240. In a particular embodiment, this is accomplished through thermal oxidation of the exposed surfaces. As a result, as shown in Figure 12A, the longitudinal microspring precursor structure 210 is typically buried. As shown in Figure 12C, the trenches 230 within each set of trenches are completely separated from each other. The transverse microspring precursor structure 212 may or may not be buried, depending on its height.

[0054] Next, in step 324 of Figure 5B and as shown in Figure 13, conductive material is deposited into the first set of trenches to form an array of first fingers 150. In step 326, conductive material is deposited into the second set of trenches to form an array of second fingers. Referring back to Figure 2B, the first arm 168 and the second arm 188 are also formed in these steps. Deposition can be performed using CVD, PVD, or other suitable methods. Examples of suitable materials include conductive materials such as polycrystalline silicon, metals, or piezoelectric materials such as barium titanate (BaTiO3, BTO), lead titanate (PbTiO3), lead zirconate titanate (PZT), or potassium sodium niobate (KNN). The first and second fingers can be made of the same or different materials, depending on the need. If they are made of the same material, only one deposition operation is required. As shown in Figure 13, a conductive material layer 254 is also formed over the top wafer.

[0055] In step 328 of Figure 5B and as shown in Figure 14, the conductive material layer is planarized to the first dielectric layer 240. The first dielectric layer acts as an etch stop layer for this step. This can be accomplished, for example, by chemical mechanical polishing (CMP), in which the surface of the wafer is planarized using the relative motion between the wafer and a rotating polishing pad to which slurry is applied. Downward pressure is applied to push the wafer against the polishing pad, and the raised components are worn away to obtain a surface with low surface roughness. As a result, the first fingers 150 are exposed.

[0056] Subsequently, in step 330 of Figure 5B and as shown in Figure 15, a dielectric layer is formed over the top wafer. This step can be considered as increasing the thickness of the first dielectric layer 240. In a particular embodiment, this is done via CVD or PVD. The addition of the first dielectric layer occurs over the first finger 150, the second finger 170 (not shown), and the other trenches 135, 137, 139, 143 in the top wafer.

[0057] Then, in step 332 of Figure 5B and as shown in Figures 16A and 16B, the first dielectric layer 240 is patterned to expose a portion of the top wafer 110 within the drive comb 134. As will be seen later, this is done to allow for later removal of silicon. A portion of the first dielectric layer is removed from the drive comb to expose the top wafer. It is worth noting that, if necessary, the patterning of the first dielectric layer can be performed in multiple steps, such that the first dielectric layer has different thicknesses in different regions on the top wafer. As shown in Figure 16A, the longitudinal pillars 222 remain buried beneath the silicon, as indicated by dashed lines. Of particular note is that the first dielectric layer is shown as being removed from region 236 between the two finger arrays, but this is not required. The first finger 150 and the second finger (not shown) remain covered by the first dielectric layer. The locations of the respective trenches 135, 137, 139, and 143 are also indicated. As shown in Figure 16B, the metal layer 206 of the lateral microspring precursor structure is also exposed.

[0058] Next, in step 334 of Figure 5B and as shown in Figure 17, a first etch stop layer 256 is deposited over 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 material of the first dielectric layer 240, such as a different dielectric or conductive material. In a particular embodiment, the first etch stop layer is made of polysilicon.

[0059] In step 336 of Figure 5B and as shown in Figure 18, a second dielectric layer 258 is formed over the first etch stop layer 256. This can be accomplished by deposition, such as CVD, PVD, or other suitable methods. Then, in step 338 of Figure 5B, as shown in Figures 19A and 19B, the second dielectric layer is patterned to expose a portion of the drive comb portion 134, the hinge portion 136, and the inner frame portion 138. In other words, the second dielectric layer is removed from these three portions. As a result, the second dielectric layer 258 remains in 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 spans the central portion 102. The first etch stop layer 256 is exposed where the second dielectric layer has been removed. In a particular embodiment, the first dielectric layer 240 and the second dielectric layer 258 are made of the same material.

[0060] Next, in step 340 of Figure 5B and as shown in Figure 20, a second etch stop layer 260 is deposited over the top wafer. Deposition can be performed using CVD, PVD, or other suitable methods. In a particular embodiment, the second etch stop layer is made of the same material as the first etch stop layer 256. Then, as shown here, there are multiple locations in the anchor arm portion 132, the drive comb portion 134, the hinge portion 136, and the inner frame portion 138 where the two etch stop layers 256, 260 are in direct contact with each other.

[0061] Then, in step 342 of Figure 5B and as shown in Figures 21A and 21B, two etch stop layers are patterned to form vertical spacers 262 within the drive comb portion. As seen here, the spacers 262 are present on a portion of the top wafer 110 between the arrays of fingers 150 and 170 in the drive comb portion 134. As shown in Figure 21A, the two etch stop layers are exposed in the region 236 between the two arrays of fingers. As shown in Figure 21B, the second dielectric layer 258 is now exposed on the inner frame portion 138, the spring portion 140, and the outer frame portion 142.

[0062] In optional step 344 of Figure 5C and as shown in Figures 22A and 22B, an opening 282 can be etched into the first finger 150 and / or the second finger 170 (not shown). The opening extends from the upper surface to the center of the finger. This can be accomplished by etching or other suitable processes (e.g., laser drilling).

[0063] In step 346 of Figure 5C and as shown in Figure 23A, metal layer 272 is deposited over top wafer 110. Deposition can be performed using CVD, PVD, or other suitable methods. Figure 23B shows the result after this deposition if optional step 344 is performed. A rivet 280 can be seen here.

[0064] Then, in step 348 of Figure 5C and as shown in Figures 24A and 24B, the metal layer is patterned to form a metal cap 196 over one or both of the two arrays of the first fingers 150. The metal layer is also patterned to remain in the center portion 102 of the other grooves 135, 137, 139, 143 in the drive comb portion 134, hinge portion 136, inner frame portion 138, spring portion 140, and outer frame portion 142. Notably, the metal cap 196 has two different heights: this can be achieved through two consecutive masking / etching steps. The location of the buried longitudinal microspring precursor structure 210 is also indicated for reference.

[0065] Next, in step 350 of Figure 5C and as shown in Figures 25A and 25B, a passivation layer 201 is formed on the metal cap 196. The passivation layer 201 is also formed on the metal layer 272 in the drive comb portion 134, hinge portion 136, inner frame portion 138, spring portion 140, and outer frame portion 142. The passivation layer can be formed by depositing another dielectric layer and patterning it to remove the dielectric layer from undesirable locations. Although not visible, the passivation layer is also present on the sides of the metal cap 196 and the metal layer 272.

[0066] Then, in step 352 of Figure 5C and as shown in Figures 26 and 27A to 27C, a cavity 112 is formed in the top wafer 110 below the array of two first fingers 150. This can be accomplished, for example, by patterning the top wafer and then etching through the exposed vertical spacers 262 (see Figure 25B) and the first dielectric layer 240 below the vertical spacers using a dry etching process as shown in Figure 26. Silicon is then completely etched using a wet etching process, as shown in Figures 27A to 27C. Some areas below the metal cap 196 and metal layer 272 are etched because they are exposed from the sides (see Figure 25A), while other areas are not exposed and therefore are not etched. In this respect, the wet etching process can be controlled by 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 is also etched in the hinge portion 136 and the spring portion 140. Some undercutting may occur, which is acceptable. As a result of this etching step, the microspring precursor structures 210, 212 are also released from the top wafer and the two etch stop layers. In the plan view of Figure 27A, portions of the bonding layer 130 and the bottom wafer 120 are also visible. As seen in Figure 27C, the top wafer is completely etched away in the region 236 between the two finger arrays, and only the longitudinal microspring precursor structure 210 remains in this region. The longitudinal pillars (formed from silicon) are etched away in this step. Any dielectric layers located on the silicon may also be removed.

[0067] Next, in step 354 of Figure 5C, annealing is performed. The annealing step can be carried out in a high-temperature heating chamber (e.g., about 800°C to about 1600°C). As a result, microsprings 202 and 204 are formed from microspring precursor structures. The resulting micromanipulator array 148 is shown in Figure 1.

[0068] In some embodiments, the package shown in Figure 1 can be used as part of a MEMS actuator. In other embodiments, the bottom wafer 120 is subsequently removed or detached from the top wafer 110. This is indicated as optional step 356 in Figure 5C, and the resulting structure is shown in Figures 28A and 28B.

[0069] 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; composites such as TiN, WN, or TaN; or alloys thereof, such as AlCu. Examples of suitable conductive oxides may include indium tin oxide (ITO), zinc oxide (ZnO), tin oxide (SnO), aluminum zinc oxide (AlZnO), indium oxide (InO), or cadmium oxide (CdO). Metallic or oxide materials may be deposited, for example, via evaporation or sputtering, electroplating, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), or other suitable methods.

[0070] The structures and methods disclosed herein also involve several different dielectric layers. Such dielectric layers can generally be made of any suitable dielectric material or combination thereof, but the properties of any particular layer can also be further defined. Examples of dielectric materials may include silicon dioxide (SiO₂), silicon nitride (Si₃N₄), silicon carbide (SiC), hafnium dioxide (HfO₂), zirconium dioxide (ZrO₂), aluminum oxide (Al₂O₃), silicon oxynitride (SiO₂xN₂y), hafnium oxynitride (HfO₂xN₂y), zirconium oxynitride (ZrO₂xN₂y), hafnium silicates (HfSi₂xO₂y), zirconium silicates (ZrSi₂xO₂y), or silicon carboxynitride (SiC₂xO₂yN₂y). (z), or hexagonal boron nitride (hBN). Other dielectric materials may include tantalum oxide (Ta₂O₅), nitrides such as silicon nitride, 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.

[0071] It should also be noted that certain routine steps have not been explicitly described in the discussion above. For example, a pattern / structure can be formed in a given layer by applying a photoresist layer, patterning the photoresist layer, developing the photoresist layer, and then etching to transfer the pattern to the given layer.

[0072] Photoresist layers can typically be applied, for example, by spin coating, or by spraying, roller coating, dip coating, or extrusion coating. In spin coating, the substrate is typically placed on a rotating platform, which may include vacuum chucks to hold the substrate in place. The photoresist composition is then applied to the center of the substrate. The speed of the rotating platform is then increased to evenly spread the photoresist from the center of the substrate to its periphery. The rotation speed of the platen is then fixed, thereby controlling the final thickness of the photoresist layer.

[0073] Next, the photoresist composition is baked or cured to remove the solvent and harden the photoresist layer. In some specific embodiments, baking is performed at a temperature of about 90°C to about 110°C. A hot plate, oven, or similar equipment can be used for baking. As a result, a photoresist layer is formed on the substrate.

[0074] The photoresist layer is then patterned through radiation exposure. The radiation can be any wavelength of light carrying the desired mask pattern. In a particular embodiment, EUV light with a wavelength of approximately 13.5 nm is used for patterning because this allows for a smaller feature size. This results in some portions of the photoresist layer being exposed to radiation, while other portions remain unexposed. This exposure causes some portions of the photoresist to become soluble in the developer, while other portions remain insoluble.

[0075] Following radiation exposure, an additional photoresist baking step (post-exposure baking, or PEB) may occur. For example, this may help release acid leaving groups (ALGs) or other molecules that are important in chemically amplified photoresists.

[0076] The photoresist layer is then developed using a developer. The developer can be an aqueous solution or an organic solvent. The soluble portions of the photoresist layer dissolve and are washed away during the development step, leaving 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, a post-development baking or "hard baking" may be performed to stabilize the developed photoresist pattern, thereby achieving optimal performance in subsequent steps.

[0077] Next, a portion of a given layer beneath the patterned photoresist layer is now exposed. Etching transfers the photoresist pattern to the given layer beneath the patterned photoresist layer. After use, the patterned photoresist layer can be removed, for example, using various solvents such as N-methyl-pyrrolidone (NMP) or alkaline media or other strippers at elevated temperatures, or by dry etching using oxygen plasma.

[0078] Generally, any etching step described herein may be performed using wet etching, dry etching, or plasma etching processes (e.g., reactive ion etching (RIE) or inductively coupled plasma (ICP) or combinations thereof), as appropriate. Etching may be anisotropic. Depending on the material, etchants may include carbon tetrafluoride (CF4), hexafluoroethane (C2F6), octafluoropropane (C3F8), fluoroform (CHF3), difluoromethane (CH2F2), fluoromethane (CH3F), carbon fluorides, nitrogen (N2), hydrogen (H2), oxygen (O2), argon (Ar), xenon (Xe), xenon difluoride (XeF2), helium (He), carbon monoxide (O), carbon dioxide (CO2), fluorine (F2), chlorine (Cl2), hydrogen bromide (HBr), and hydrofluoric acid. Hydrofluoric acid (HF), nitrogen trifluoride (NF₃), sulfur hexafluoride (SF₆), boron trichloride (BCl₃), ammonia (NH₃), bromine (Br₂), etc., or combinations thereof in various proportions. For example, silicon dioxide can be wet-etched using hydrofluoric acid and ammonium fluoride. Alternatively, silicon dioxide can be dry-etched using various mixtures of CHF₃, O₂, CF₄, and / or H₂.

[0079] Continuing, Figure 29 is a flowchart illustrating a more general method 360 for manufacturing an arm array that can be used, for example, in a MEMS actuator, according to some embodiments.

[0080] In step 362 of Figure 29, an array of multiple first fingers 150 is formed on wafer 110 using a conductive material. In step 364, an array of multiple second fingers 170 is formed on wafer 110 using a conductive material. The distal ends 160 of the first finger array and the distal ends 180 of the second finger array are offset from each other in one horizontal direction and separated from each other in another horizontal direction. This structure is illustrated in Figures 7A to 7C. If the two finger arrays are made of the same material, they can be formed in a single process step.

[0081] In step 366 of Figure 29, the microspring precursor structure 210 is formed between the distal ends 160, 180 of the first and second fingers. The microspring precursor structure 210 can also be described as being formed on a columnar structure 222 located at the ends of the two sets of grooves 230, 232. This structure is shown in Figures 11A and 11C.

[0082] In step 368 of Figure 29, a microspring precursor structure 212 is formed between adjacent first fingers 150. The microspring precursor structure 212 can also be described as being formed on a column 224 between two adjacent grooves 230. This structure is shown in Figure 11B. In step 370 of Figure 29, the microspring precursor structure 212 is formed between adjacent second fingers.

[0083] In step 372 of Figure 29, a metal cap 196 is formed to connect the first fingers 150 together. This structure is shown in Figures 24A and 24B. In step 374 of Figure 29, a metal cap is formed to connect the second fingers together.

[0084] In step 376 of Figure 29, wafer 110 is etched to form cavity 112 beneath the first and second finger arrays. This structure is shown in Figures 27A and 27B. Note that the microspring precursor structures 210, 212 are now exposed.

[0085] In step 378 of Figure 29, annealing is performed to transform each microspring precursor structure into microsprings 202, 204. The resulting structure is shown in Figure 1. Method 360 may also include any of the method steps mentioned in Figures 5A through 5C.

[0086] Continuing, Figure 30 is a flowchart illustrating another general method 380 for manufacturing an arm array for a device such as a MEMS actuator, according to some embodiments. In this method, rivets 280 are present.

[0087] In step 382 of Figure 30, an array of first fingers 150 is formed on wafer 110. In step 384, an array of second fingers 170 is formed on wafer 110. The distal ends 160 of the first finger array and the distal ends 180 of the second finger array can be separated from each other or inserted between each other. This structure is shown in Figures 4A and 4B.

[0088] In step 386 of Figure 30, a microspring precursor structure 212 is formed between adjacent first fingers 150 and second fingers 170. The microspring precursor structure 212 can also be described as being formed on a columnar structure 224 between two sets of grooves 230, 232. In step 388 of Figure 30, the microspring precursor structure 212 is formed between adjacent first fingers or adjacent second fingers.

[0089] In step 390 of Figure 30, an opening 282 is formed in the first finger and / or the second finger. This is shown in Figures 22A and 22B. In step 392, a metal cap 196 is formed that contacts the first finger 150 in the array of first fingers. A rivet extending to the finger is also formed. In step 394, a metal cap 197 is formed that contacts the second finger 170 in the array of second fingers. A rivet extending to the second finger is also formed. This is schematically shown in Figures 4B and 23B. It is contemplated that steps 392 and 394 can be combined into one step if the metal cap 196 contacts both the first finger 150 and the second finger 170, as shown in Figure 4C.

[0090] In step 396, wafer 110 is etched to form a cavity 112 beneath the first and second finger arrays. In step 398, annealing is performed to transform each microspring precursor structure into microsprings 202, 204. The resulting structure is shown in Figure 1. Method 380 may also include any of the method steps mentioned in Figures 5A through 5C.

[0091] Continuing, Figure 31 is a plan view of a MEMS 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 member 404. The sensor connection member 404 includes a centrally located anchor 406. As shown here, four anchor arms 407 extend from the anchor, and together they can be considered as an anchor structure 408.

[0092] The sensor connection component 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 the 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 can exist. In a particular embodiment, the drive comb section may contain one to ten micro-robotic arm arrays. The length of the drive comb section opposite the anchor arms 407 can serve as a support member 410. Hinges 412 or cantilever arms extend through the open space to connect the support member 410 to a non-adjacent corner of the frame 402. Sensor mounts 414 are also located on each support member.

[0093] Box 416 generally indicates the position of the views in Figures 6 through 28B relative to the entire actuator, and the above-described processing steps can be applied to the remaining parts of the MEMS actuator. The anchor arm portion 132, drive comb portion 134, hinge portion 136, inner frame portion 138, spring portion 140, and outer frame portion 142 of Figure 1 are also shown here. Anchor arm portion 132 is part of anchor arm 407. Inner frame portion 138, spring portion 140, and outer frame portion 142 constitute part of the actuator frame 402. The overall dimensions of a MEMS actuator are typically in the millimeter range, for example, less than 20 mm x 20 mm.

[0094] MEMS actuators are extremely useful for optical image stabilization (OIS). OIS is used to reduce blurring that can occur due to movement of the imaging device during exposure, such as binoculars, cameras (handheld, still, or video), telescopes, and mobile phones / smartphones. This movement causes light initially detected in one pixel to move to an adjacent pixel, which appears as blur in the captured image. As pixel size decreases, the blur becomes more noticeable at high resolutions. In this disclosure, OIS is performed by moving the image sensor to compensate for changes in the optical path. This is likely preferable to moving the lens because it reduces the weight and complexity of the lens, and the compensation can be much faster (approximately a few milliseconds instead of tens of milliseconds). The MEMS actuator can move on all five axes (i.e., X, Y, roll, yaw, and pitch).

[0095] Figure 32 is a flowchart illustrating a method 440 for stabilizing an optical image against external movement according to some embodiments. This method is performed using a MEMS actuator as shown in Figure 31. Some steps of this method are also shown in Figures 33A and 33B.

[0096] First, Figure 33A is a side cross-sectional view of an optical image capturing device 418. This device includes a MEMS actuator 400 located within a housing 420 as previously described. A sensor connection member 404 is labeled. Two sensor mounts 414 are also shown, and an image sensor 422 is mounted on the MEMS actuator via attachment to the sensor mounts 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 light falls on the image sensor. Here, the image sensor 422 is in a first position, and an illumination path exists between the lens 424 and the image sensor 422.

[0097] When the device / casing is subjected to external movement, such as shaking from the user's hand, in step 442 of Figure 32, the MEMS actuator is moved to compensate for the external movement. This can be accomplished, for example, by sending electrical signals to a micromanipulator array in one or more quadrants to change the physical distance between the first and second finger arrays. As shown in Figure 33B, this causes the sensor connection part 404 of the actuator 400 to tilt relative to the frame, which moves the image sensor 422 to a second position such that the optical path still hits the same position on the image sensor.

[0098] The longitudinal microspring arm array structure is more stable and less prone to breakage. Due to their relatively large amplitude, they can withstand greater pressure / stress without cracking. Furthermore, since many fingers have three to four microsprings, even if, for example, 50% of the microsprings fail, the entire array will still maintain up to 90-99% efficiency, rather than a 50% loss. This extends the device's lifespan and improves customer satisfaction.

[0099] Therefore, some embodiments of this disclosure relate to various methods for fabricating arm arrays for devices such as MEMS actuators. A first finger array and a second finger array are formed on a wafer. The first finger array and the second finger array are separated from each other by lateral trenches. For each finger in the first finger array, at least one longitudinal microspring precursor structure is formed with an adjacent finger in the second finger array. A cavity is then formed in the wafer beneath the first finger array and the second finger array. Annealing is performed to transform each longitudinal microspring precursor structure into a longitudinal microspring.

[0100] In a further embodiment, each arm array further includes: a transverse microspring connecting adjacent fingers within the same array; or, a metal cap above the first or second finger array.

[0101] Furthermore, the first and second finger arrays are located within the drive comb section. The arm array may also include an anchor arm portion, a hinge portion, an inner frame portion, a spring portion, and an outer frame portion connected to the anchor structure.

[0102] Various embodiments described herein also illustrate methods for stabilizing optical images against external movement. This is accomplished by moving a MEMS actuator equipped with an image sensor to compensate for external movement. The MEMS actuator comprises an array of multiple micro-robotic arms connected to an anchoring structure, each arm array having the components described above.

[0103] In various embodiments, this disclosure also relates to an optical image capturing device comprising: an image sensor mounted to a MEMS actuator; and a lens positioned such that the image sensor is located between the lens and the MEMS actuator. The MEMS actuator includes an array of multiple micromanipulator arms connected to an anchor structure. Each arm array includes a first array of fingers and a second array of fingers. The first array of spaced-apart fingers extends longitudinally from a first arm. The second array of spaced-apart fingers extends longitudinally from a second arm. The first and second arrays of fingers are separated from each other by transverse grooves. One or more longitudinal microsprings connect each finger in the first array of fingers to an adjacent finger in the second array of fingers.

[0104] Some embodiments disclosed herein also relate to various methods for fabricating arm arrays, for example, that could be used in devices such as MEMS actuators. A first finger array and a second finger array are formed on a wafer. Openings are formed in the first and / or second fingers. Deposition and patterning of a metal layer results in the formation of metal caps on the first and / or second fingers, with rivets extending into the openings. A cavity is then formed in the wafer beneath the first and second finger arrays. Optionally, microspring precursor structures are formed, and annealing is performed to transform each microspring precursor structure into a microspring.

[0105] Other embodiments disclosed herein relate to various methods for fabricating arm arrays (e.g., for MEMS actuators). A package including a top wafer bonded to a bottom wafer is received. The top wafer is patterned to form a first set of trenches, a second set of trenches, and at least one pillar. A dielectric layer is formed on the exposed surfaces of the first set of trenches, the second set of trenches, and at least one pillar. A metal layer is formed on at least one pillar to obtain at least one microspring precursor structure. Optionally, at least one sacrificial spacer is formed on at least one microspring precursor structure. A dielectric layer is then formed on the exposed surfaces of the at least one microspring precursor structure and at least one sacrificial spacer. A conductive material is deposited into the first set of trenches to form an array of first fingers. A conductive material is deposited into the second set of trenches to form an array of second fingers. Openings are formed in at least two fingers in the first finger array. A metal cap fills the openings in at least two fingers in the first finger array to form rivets. Etching is performed to remove at least one optional sacrificial spacer and form a cavity within the top wafer. Annealing is performed to transform each microspring precursor structure into a microspring.

[0106] Various embodiments described herein also include devices such as MEMS actuators comprising an anchor structure. Multiple arm arrays are connected to the anchor structure. Each arm array includes a first finger array and a second finger array. The first array of spaced-apart fingers extends longitudinally from the first arm. The second array of spaced-apart fingers extends longitudinally from the second arm. The distal ends of the first and second fingers may be separated from each other by transverse grooves, or they may be inserted into each other. A metal cap extends over the finger arrays. The metal cap includes rivets extending to at least two of the first fingers.

[0107] In a further embodiment, each arm array further includes: a microspring connecting each first finger to an adjacent second finger; and / or a microspring connecting each finger to an adjacent finger.

[0108] Furthermore, the first and second finger arrays are located within the drive comb section. The arm array may also include an anchor arm section, a hinge section, an inner frame section, a spring section, and an outer frame section connected to the anchor structure.

[0109] Various embodiments described herein also illustrate methods for stabilizing optical images against external movement. This is accomplished by moving a MEMS actuator, on which an image sensor is mounted to compensate for external movement. The MEMS actuator comprises an array of multiple micro-robotic arms connected to an anchor structure, each arm array having a metal cap with rivets as described above.

[0110] Finally, this disclosure also relates, in various embodiments, to an optical image capturing device comprising: an image sensor mounted to a MEMS actuator; and a lens positioned such that the image sensor is located between the lens and the MEMS actuator. The MEMS actuator includes an array of multiple micromanipulator arms connected to an anchor structure. Each arm array includes a first array of fingers and a second array of fingers. The first array of spaced-apart fingers extends longitudinally from the first arm. The spaced-apart fingers of the second array extend longitudinally from the second arm. The distal ends of the first and second fingers may be separated from each other by transverse grooves, or they may be inserted into each other. A metal cap extends over the array of fingers. The metal cap includes rivets extending to at least two of the first fingers.

[0111] The foregoing outlines the features of several embodiments or examples to enable those skilled in the art to better understand the nature of this disclosure. Those skilled in the art should recognize that they can readily use this disclosure as a basis to design or modify other processes and structures that perform the same purpose and / or achieve the same advantages of the embodiments or examples described herein. Those skilled in the art should also recognize that such equivalent constructions do not depart from the spirit and scope of this disclosure, and that various changes, substitutions, and modifications can be made herein without departing from the spirit and scope of this disclosure.

[0112] 100: Package 102: Central Part 110: Top wafer 112: Cavity 114: Top surface 115: Thickness 120: Bottom wafer 122: Cavity 125: Thickness 130: Bonding layer 132: Anchor arm section 134: Drive comb section 135: Groove 136: Hinge section 137: Trench 138: Inner Frame Section 139: Trench 140: Spring section 142: Outer frame section 143: Trench 148: Microrobotic Arm Array 150: First finger-like object 152:Core 154: Overlay 156: Free End 158: Fixed end 160: Remote 162: Proximal 163: Height 165: Width 167: Length 168: First Arm 170: Second finger-like structure 176: Free End 178: Fixed end 180: Remote 182: Proximal 183: Height 187: Length 188: Second Arm 190: First finger-like structure 191: First finger-like object 192: First finger-like structure 193: Second finger-like structure 194: Second finger-like structure 195: Distance 196: Metal Cap 197: Metal Cap 198: Top surface 199: Width 200: Width 201: Passivation layer 202: Micro Spring 203: Length 204: Lateral Micro Spring 205: Width 206: Metal layer 208: Dielectric layer 210: Longitudinal micro-spring precursor structure 212: Lateral Micro-Spring Precursor Structure 214: First Direction 216: Second Direction 222: Longitudinal column 224: Horizontal column 230: Trench 232: Trench 234: Trench 236: Area 240: First dielectric layer 242: Metal 244: Sacrificial Materials 246: Sacrificial spacer 254: Conductive material layer 256: First Etching Stop Layer 258: Second dielectric layer 260: Second etch stop layer 262: Spacer 272: Metal layer 280: Rivet 281: Top Width 282: Opening 283: Bottom width 285: Height 300: Method 302: Steps 304: Steps 306: Steps 308: Steps 310: Steps 312: Steps 314: Steps 316: Steps 318: Steps 320: Steps 322: Steps 324: Steps 326: Steps 328: Steps 330: Steps 332: Steps 334: Steps 336: Steps 338: Steps 340: Steps 342: Steps 344: Steps 346: Steps 348: Steps 350: Steps 352: Steps 354: Steps 356: Steps 360: Method 362: Steps 364: Steps 366: Steps 368: Steps 370: Steps 372: Steps 374: Steps 376: Steps 378: Steps 380: Method 382: Steps 384: Steps 386: Steps 388: Steps 390: Steps 392: Steps 394: Steps 396: Steps 398: Steps 400: Actuator 402: Frame 404: Sensor connection component 406: Anchor 407: Anchor Arm 408: Anchor Structure 410: Support component 412: Hinges 414: Sensor mounting hardware 416: Box 418: Optical image capturing device 420: Outer shell 422: Image Sensor 424: Lens 440: Method 442: Steps BB: Line CC: Line X: axis Y: axis Z: Axis

Claims

1. A method for fabricating an arm array, comprising: An array of multiple first fingers and an array of multiple second fingers are formed on a wafer, wherein the array of first fingers and the array of second fingers are separated from each other by a lateral trench; for each finger in the array of first fingers, at least one longitudinal microspring precursor structure is formed with an adjacent finger in the array of second fingers; a cavity is formed in the wafer below the array of first fingers and the array of second fingers; and annealing is performed to transform each longitudinal microspring precursor structure into a longitudinal microspring.

2. The method of manufacturing the arm array as described in claim 1 further includes forming a metal cap in contact with each of the first fingers in the array.

3. The method of fabricating an arm array as claimed in claim 1, wherein the at least one longitudinal microspring precursor structure is formed by: patterning the wafer to form a pillar in the lateral trench, the lateral trench extending from the first fingers in the array of the first fingers to a distal end of an adjacent finger in the array of the second fingers; forming a dielectric layer on the pillar; and forming a metal layer on the pillar to obtain the at least one longitudinal microspring precursor structure.

4. The method for manufacturing the arm array as described in claim 1 further includes: For each of the first fingers in the array, at least one transverse microspring precursor structure is formed with an adjacent finger in the array of the first fingers.

5. A device including an arm array, comprising: One-anchor structure; And a plurality of arm arrays connected to the anchor structure, each arm array comprising: a first array of spaced-apart fingers extending longitudinally from a first arm; A second array of spaced-apart fingers extends longitudinally from a second arm, wherein the first array of spaced-apart fingers and the second array of spaced-apart fingers are separated from each other by a transverse groove; and one or more longitudinal microsprings connect each finger in the first array of spaced-apart fingers to a plurality of adjacent fingers in the second array of spaced-apart fingers.

6. The apparatus comprising an arm array as described in claim 5, wherein each arm array further comprises: Multiple transverse microsprings connect each finger in the first array of the fingers to multiple adjacent fingers in the second array of the fingers; and a metal cap is located above at least two fingers in the first array of the fingers.

7. A method for fabricating an arm array, comprising: Receive a package comprising a top wafer bonded to a bottom wafer; The top wafer is patterned to form a first set of trenches, a second set of trenches, and at least one pillar; a dielectric layer is formed on multiple exposed surfaces of the first set of trenches, the second set of trenches, and the at least one pillar; a metal layer is formed on the at least one pillar to obtain at least one microspring precursor structure; at least one sacrificial spacer is selectively formed on the at least one microspring precursor structure, and a dielectric layer is formed on multiple exposed surfaces of the at least one microspring precursor structure and the at least one sacrificial spacer; a conductive material is deposited in the first set of trenches to form an array of multiple first fingers; a conductive material is deposited in the second set of trenches to form an array of multiple second fingers; multiple openings are formed in at least two fingers of the array of first fingers; a metal cap is formed to fill the openings in the at least two fingers of the array of first fingers to form multiple rivets; Etching to remove the selectively sacrificial spacer and form a cavity within the top wafer; and annealing to transform each microspring precursor structure into a microspring.

8. A method of manufacturing an arm array as described in claim 7, wherein the plurality of distal ends of the array of the first fingers and the plurality of distal ends of the array of the second fingers are interposed between each other.

9. A method of manufacturing an arm array as claimed in claim 7, wherein a plurality of proximal ends of the array of the first fingers extend in a first direction and are connected to a first arm, and a plurality of proximal ends of the array of the second fingers extend in a second direction opposite to the first direction and are connected to a second arm.

10. The method of fabricating the arm array as described in claim 7 further includes forming a passivation layer over the metal cap.

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