A MEMS-based in-plane triaxial large displacement actuation platform and a manufacturing method thereof

Abstract

The application discloses a MEMS-based in-plane three-axis large displacement actuating platform and a manufacturing method thereof, mainly comprising an outer frame, a cross island frame, a bidirectional comb-shaped driving unit, a long spring beam and a short spring beam, and manufacturing steps comprise: using magnetic neutral loop discharge plasma (NLD) to anisotropically etch a cavity structure on a glass substrate, using an anode bonding process to bond a BF33 glass wafer with the cavity structure and a low-resistance silicon wafer, thinning the low-resistance silicon wafer, deep silicon etching (DRIE) the low-resistance silicon wafer to form an electrically isolated channel and fill BCB material, using a chemical mechanical polishing (CMP) process to remove the BCB on the surface of the low-resistance silicon wafer, sputtering a metal layer and using a lift-off process to form a wire layer, and deep silicon etching (DRIE) the low-resistance silicon wafer to form a final device. The application has the beneficial effects of improving device filling rate, reducing size, improving structural stiffness, response speed, resonance frequency and heat dissipation performance, and simultaneously providing a wire bonding method for heterogeneously integrating a micro moving platform and a CMOS chip.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of micro-electro-mechanical system (MEMS), and particularly relates to an in-plane three-axis large displacement actuation platform based on MEMS and a manufacturing method thereof. BACKGROUND

[0002] Image stabilization (IS) is a key technology to improve image quality, mainly divided into two categories: software-based image stabilization and hardware-based image stabilization. Software-based image stabilization includes digital image stabilization (DIS) and electronic image stabilization (EIS), which process image data through software algorithms to reduce image blur caused by camera shake or hand jitter. Specifically, the digital image stabilization (DIS) technology relies on image post-processing algorithms to correct the shake, which analyzes the motion between image frames to correct the shake of the photographed image, focusing on optimization after shooting. While the electronic image stabilization (EIS) technology performs image stabilization in real time during shooting, which needs to combine the built-in sensors (such as accelerometers and gyroscopes) of the mobile phone to obtain the real-time dynamic data of the device, and use software algorithms to process the image, including adjusting image frames, cropping, aligning and synthesizing, etc., to reduce the shake and improve the image quality. Hardware-based image stabilization includes optical image stabilization (OIS) and mechanical anti-shake. OIS acquires device motion information in real time through accelerometers and gyroscopes, and adjusts the position of the lens or sensor to compensate for camera shake; while mechanical anti-shake physically stabilizes the device through external equipment (such as a gimbal), further reducing the shake during shooting and ensuring more stable imaging results.

[0003] Micro-electro-mechanical system (MEMS) is a technology that combines electronic components with moving parts. It uses microfabrication techniques to create microscale mechanical and electronic structures, allowing devices using MEMS to achieve miniaturization while performing complex functions. MEMS-based actuators have gradually been applied to camera anti-shake of smartphones. The invention patent application with application number 2016106283145 and name Multi-directional Actuator discloses a MEMS multi-directional actuator composed of an inner and outer frame and a bidirectional comb-shaped driving unit, which is driven by a comb-shaped driving actuator to drive the inner frame to move relative to the outer frame in X and Y axes and rotate around Z axis, with three degrees of freedom. Currently, the technology of inner and outer frames and bidirectional comb-shaped driving units has been widely applied in the field of camera anti-shake, especially in the camera modules of high-end smartphones. In actual application, some technical problems still exist in the structure of inner and outer frames, which need to be improved.

[0004] 1. Miniaturization is limited. The separate moving frame structure usually needs to set a larger gap between the moving frame and the driving platform to accommodate the long spring beam. Since the length of the long spring beam is longer (usually 1 to 1.5 times of the current design), it means that the moving frame structure will occupy more space in size, thereby limiting the miniaturization of the overall system.

[0005] 2. Low response speed and resonance frequency. The long spring beam reduces the stiffness of the system in structure, resulting in the decrease of the resonance frequency. The deformation of the long beam is large when it is under stress, and the rebound is slow, which leads to the decrease of the response speed of the system and the inability to quickly respond to external control signals. SUMMARY

[0006] In view of the technical problems existing in the internal and external double frame structure of the current MEMS actuator, a MEMS-based in-plane three-axis large displacement actuation platform and a manufacturing method thereof are provided.

[0007] The application is implemented by the following technical solutions:

[0008] A MEMS-based in-plane three-axis large displacement actuation platform: comprising an outer frame, a cross island frame, a bidirectional comb-shaped driving unit, a long spring beam and a short spring beam;

[0009] The outer frame comprises a cavity for accommodating the cross island frame and a cavity for accommodating the bidirectional comb-shaped driving unit;

[0010] The cross island frame comprises a cross and a crossbar, wherein the crossbar has four crossbars arranged at the outer end positions of the cross;

[0011] The bidirectional comb-shaped driving unit is composed of a stator and a rotor, the stator has an open slot, the left side of the open slot has a first left comb-shaped array, and the right side of the open slot has a first right comb-shaped array, the rotor has a rectangular protruding block, the left side of the rectangular protruding block has a second left comb-shaped array, and the right side of the rectangular protruding block has a second right comb-shaped array, the rectangular protruding block is inserted into the middle of the open slot, the first left comb-shaped array and the second left comb-shaped array are interpenetrated and have a gap, and the first right comb-shaped array and the second right comb-shaped array are interpenetrated and have a gap;

[0012] One end of the short spring beam is connected to the rotor, and the other end is connected to the stator;

[0013] One end of the long spring beam is connected to the rotor, and the other end is connected to the cross island frame;

[0014] The number of bidirectional comb-shaped driving units is four, which are respectively located in the four quadrant positions of the cross island frame, each bidirectional comb-shaped driving unit is connected to the cross island frame through the long spring beam, and each adjacent two of the four bidirectional comb-shaped driving units are arranged at an angle of ninety degrees.

[0015] The in-plane three-axis large displacement actuation platform based on MEMS has protruding extension parts on the left and right sides of the middle part of the rectangular convex block to form limiting blocks, and an opening slot in the middle forms a limiting slot, and the limiting blocks are located in the limiting slot.

[0016] The in-plane three-axis large displacement actuation platform based on MEMS has one-to-one correspondence between the opening slot on the stator and the rectangular convex block on the rotor, two for a pair, and the stator has three opening slots, and the rotor has three rectangular convex blocks corresponding to the opening slots, and each opening slot and rectangular convex block has a matching comb-shaped array.

[0017] A manufacturing method of an in-plane three-axis large displacement actuation platform based on MEMS, the in-plane three-axis large displacement actuation platform based on MEMS includes an outer frame, a cross island frame, a bidirectional comb-shaped driving unit, a long spring beam and a short spring beam, and comprises the following steps:

[0018] Step one: etching of the glass substrate;

[0019] A piece of BF33 glass is spin-coated with photoresist after organic cleaning, and the photoresist is photoetched in a photoetching machine through a mask plate;

[0020] Step two: etching a cavity structure by using a magnetic neutral loop discharge plasma (NLD) anisotropic etching technology, and removing the photoresist by wet method;

[0021] Step three: bonding the side of the BF33 glass wafer with the cavity structure with a low-resistance silicon wafer by using an anode bonding process;

[0022] Step four: thinning the low-resistance silicon wafer surface of the bonded wafer using a thinning machine;

[0023] Step five: etching an electric isolation channel in the low-resistance silicon, cutting the stator from the low-resistance silicon to form an independent part, and cutting the left and right comb-shaped arrays of the stator into two independent parts to realize electrical isolation, and then etching the electric isolation channel at the set position, and the electric isolation channel at the lower side of the left and right comb-shaped arrays is in U shape;

[0024] Step six: filling the BCB material in the electric isolation channel, bonding the cut and separated left and right comb-shaped arrays into one whole, bonding the right comb-shaped array and the low-resistance silicon into one whole, vacuuming the BCB liquid into the isolation channel of the etched low-resistance silicon as an insulating layer, and high-temperature curing the BCB material, removing the BCB on the surface of the low-resistance silicon by chemical mechanical polishing (CMP) process, and only keeping the BCB material in the channel;

[0025] Step seven: PECVD oxide layer deposition on low resistance silicon, respectively, left side comb array one way and right side comb array one way;

[0026] Step eight: sputtering metal layer and using lift-off process to make metal wire layer, to lay three circuits, stator left side comb array one way, stator right side comb array one way and mover comb array one way, wherein the metal layer of stator left side comb array one way and right side comb array one way is laid on the insulating layer PECVD oxide layer, and the mover comb array is integrated with the whole low resistance silicon, and the circuit is directly led out on the low resistance silicon;

[0027] Step nine: deep silicon etching process to etch low resistance silicon, first spin-coating photoresist, then being photoetched in a photoetching machine through a mask plate, deep silicon etching low resistance silicon, while etching out a cross island frame, a bidirectional comb driving unit, a long spring beam and a short spring beam, and a plurality of process beams, one end of the process beam being connected to the cross island frame, and the other end being connected to an outer frame.

[0028] The beneficial effects of the present application are:

[0029] 1. Through the compact driving unit layout, the cross island frame is surrounded by four driving units, which improves the filling rate of the platform, reduces the size of the device, makes it easier to miniaturize, and is suitable for high-integration microelectronic equipment applications;

[0030] 2. Through the design of the cross island frame, the inner frame structure is replaced, the length of the spring beam is effectively reduced, the device stiffness and response speed are improved; at the same time, the resonant frequency is improved, the imaging quality of the device under high-frequency jitter is improved, and the image stabilization technology is better applied;

[0031] 3. Through the design of the process beam, not only the heat dissipation performance of the device in the deep silicon etching (DRIE) process is improved, the etching yield of the device is improved, but also the structural strength of the device in the transportation process is enhanced. In addition, when the device is subjected to wire bonding packaging process, the structure is easily damaged due to the impact of wire bonding, the design of the process beam improves the stability and reliability of the device structure in the wire bonding packaging process, and effectively improves the success rate of heterogeneous integration. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of an embodiment of the present application;

[0033] Figure 2 It is an outer frame structure schematic diagram of an embodiment of the present application;

[0034] Figure 3 It is a cross island frame schematic diagram of an embodiment of the present application;

[0035] Figure 4 It is a stator schematic diagram of an embodiment of the present application;

[0036] Figure 5 A schematic diagram of a comb drive unit of one comb array of an embodiment of the present application;

[0037] Figure 6 A schematic diagram of a comb drive unit of three comb arrays of an embodiment of the present application;

[0038] Figure 7 A cross-sectional view and a top view of a glass etching step in the manufacturing of an actuation platform of an embodiment of the present application;

[0039] Figure 8 A cross-sectional view of a device in the manufacturing of an actuation platform of an embodiment of the present application;

[0040] Figure 9 A schematic diagram of a stator cutting line and a BCB material filling position of the present application;

[0041] Figure 10 A schematic diagram of a linear cutting opening filled with BCB material of the present application;

[0042] Figure 11 A schematic diagram of a U-shaped cutting opening filled with BCB material of the present application; Figure 10 A schematic diagram of a sputtering metal material process of the present application;

[0043] Figure 12 A schematic diagram of a U-shaped cutting opening filled with BCB material of the present application;

[0044] Figure 13 A schematic diagram of a sputtering metal material of the present application;

[0045] Figure 14 A schematic diagram of a sputtering metal material of a micro-actuation platform of the present application. DETAILED DESCRIPTION

[0046] In order to make the technical problems solved by the present application, the technical solutions adopted and the technical effects reached more clear, the technical solutions of the present application will be further described below in conjunction with the accompanying drawings and through specific embodiments. It can be understood that the specific embodiments described here are only used to explain the present application, but not to limit the present application. In addition, it should be noted that, in order to facilitate the description, only the parts related to the present application are shown in the drawings, but not all.

[0047] Referring to Figures 1-14 , the present embodiment provides a MEMS-based in-plane three-axis large displacement actuation platform and a manufacturing method thereof.

[0048] As shown in Figure 1 , the MEMS-based in-plane three-axis large displacement actuation platform comprises an outer frame 1, a cross island frame 2, a bidirectional comb drive unit 3, a long spring beam 4 and a short spring beam 5.

[0049] AsFigure 2 As shown, the outer frame 1 is removed material to form a cavity for accommodating the cross island frame 2, and the removed material forms a cavity for accommodating the bidirectional comb drive unit 3.

[0050] As shown, Figure 3 As shown, the cross island frame 2 includes a cross 21 and a crossbar 22, and the crossbar 22 is provided with four crossbars respectively arranged at the outer end of the cross 21.

[0051] As shown, Figure 4 As shown, the bidirectional comb drive brake 3 is composed of a stator 31 and a rotor 32, as shown, Figure 4 As shown, the stator 31 has an open slot 40, the left side of the open slot 40 has a first left comb array 41, the right side has a first right comb array 42, and the middle of the open slot 40 forms a limiting slot 43.

[0052] As shown, Figure 5 As shown, the rotor 32 has a rectangular protruding block 33, the left side of the rectangular protruding block has a second left comb array 34, the right side has a second right comb array 35, and the middle part of the rectangular protruding block 33 is provided with protruding extension parts on both sides to form a limiting block 36. The rectangular protruding block 33 is inserted into the middle of the open slot 40, the first left comb array 41 and the second left comb array 34 are interpenetrated but not in contact with each other, the first right comb array 42 and the second right comb array 35 are interpenetrated but not in contact with each other, and the limiting block 36 is located in the limiting slot 43, which plays a limiting role, preventing the comb array of the rotor and the comb array of the stator from generating a side wall suction effect and contacting each other to cause short circuit.

[0053] The short spring beam 5 is connected to the rotor 32 at one end and to the stator 31 at the other end. The long spring beam 4 is connected to the rotor 32 at one end and to the cross island frame 2 at the other end. In this way, by applying voltage to the comb arrays on the rotor 32 and the stator 31 through the circuit, the rotor is driven to move relative to the stator, and the driving force is applied to the cross island frame through the action of the long spring beam 4, thereby achieving the driving of the cross island frame.

[0054] The driving mode of the bidirectional comb drive actuator is described as shown, Figure 5 As shown, when the first left comb array 41 and the second left comb array 34 are electrified, the rotor 32 will move to the left along the X axis due to the action of electrostatic force. Conversely, when the first right comb array 42 and the second right comb array 35 are electrified, the rotor 32 will move to the right along the X axis due to the action of electrostatic force.

[0055] The open slots 40 on the stator and the rectangular protruding blocks 33 on the mover correspond one by one, two for a pair, that is, bidirectional driving can be realized. In order to increase the driving force, the number of open slots and rectangular protruding blocks between them can also be increased. With the increase of open slots and rectangular protruding blocks, it means the increase of the number of comb arrays, and the increase of the number of comb arrays means the increase of electrostatic force. As shown in Figure 6 The stator has a total of three open slots, and the mover has three rectangular protruding blocks 33 corresponding to them. In this way, a larger driving force is obtained.

[0056] As shown in Figure 1 The four bidirectional comb drive actuators 3 are located in the four quadrant positions of the cross island frame, and each bidirectional comb drive unit 3 is connected to the cross island frame 2 through a long spring beam 4. The four bidirectional comb drive units 3 are arranged at an angle of 90 degrees to each other, which ensures the uniformity and consistency of the platform movement in all directions, greatly improving the motion control accuracy of the platform. The angle of 90 degrees is the angle of the moving direction of the stator. The driving units in the upper left corner and the lower right corner control the displacement in the X-axis direction, while the driving units in the upper right corner and the lower left corner control the displacement in the Y-axis direction. The platform can realize independent and accurate in-plane motion in the X-axis and Y-axis directions.

[0057] By controlling the differential motion of the four driving units, in-plane rotation control of the cross island platform can be achieved. This innovative design provides more flexible two-dimensional motion control while maintaining high precision. Through the compact layout of the driving units, the cross island structure is surrounded by four units, which improves the fill factor of the platform, reduces the size of the device, and makes it easier to miniaturize, suitable for high-integration microelectronic equipment applications.

[0058] The specific moving method of the cross island platform is as follows:

[0059] The cross island moves left along the X-axis: the left comb array of driving units A and C is powered on;

[0060] The cross island moves up along the Y-axis: the upper comb array of driving units B and D is powered on;

[0061] The cross island rotates clockwise along the Z-axis: the right comb array of driving unit A, the lower comb array of driving unit B, the left comb array of driving unit C, and the upper comb array of driving unit D are powered on. Similarly, other directions of movement can be obtained by exchanging the powered comb arrays, which will not be repeated here. It should be noted that when one side of the comb array of the driving unit is powered on, the other side of the comb array is not powered on.

[0062] In Figure 1The structure of each driving unit has three open slots on the stator, and each open slot has a comb-shaped array on both left and right sides. From the above introduction, it can be known that: first, both the left and right comb-shaped arrays need to be powered to drive, and the power supply needs to lay a circuit; second, the circuits of the left and right comb-shaped arrays need to be isolated from each other, and the right side cannot be powered when the left side is powered; third, the left comb-shaped arrays of the three open slots should be connected as a whole, and need to be connected through a circuit.

[0063] In the processing of the in-plane three-axis large displacement actuation platform of MEMS, three technical problems are encountered. One is how to isolate the left and right comb-shaped arrays of the three open slots to form two mutually isolated circuits. One is how to electrically connect the left comb-shaped arrays of the three open slots into a whole through a circuit. The last one is that a large amount of heat will be generated during the processing of so many comb-shaped arrays, which will burn the weak places of the device if the heat dissipation is poor, affecting the yield of the product.

[0064] First, the stator is isolated from the circuit of the mover. The method adopted is to cut off the stator from the whole part, so that the stator is isolated from the part to form an isolated block, as shown in Figure 9 , and then bonded together with benzocyclobutene resin (BCB) material, which not only ensures insulation but also ensures a whole. The mover is connected to the whole part through a long spring beam. The second step is to cut out the three left comb-shaped arrays on the stator separately to form three independent blocks. As shown in Figure 9 , the white part is the cutting knife path. The black part is also the cutting knife path. The reason why it is black is that after the white cutting knife path, BCB material is filled to bond the isolated blocks cut out together, but keep the state of mutual insulation. Then an insulating layer is laid, and a conductive metal is laid on the insulating layer to connect the left comb-shaped arrays together to form an electrically connected whole.

[0065] As shown in Figure 10 , in the actual processing process, a one-letter-shaped cutting port is initially used, and after filling the BCB material in the cutting port and bonding, an insulating material such as silicon dioxide is covered. Finally, a conductive metal material is deposited. It is found through experiments that this process method has a low product yield. After analysis, it is found that the insulating material (silicon dioxide) at both ends of the one-letter-shaped cutting port will fall off to different degrees during wet etching, causing the low-resistance silicon layer under the insulating material to be exposed, and the exposed silicon layer will connect the left and right sides when covering the metal conductive layer, as shown in Figure 11 , which eventually causes the process to fail. After repeated experiments, a scheme of U-shaped cutting port is proposed, as shown in Figure 12As shown, the knife edge design with a U-shaped mouth is adopted, although the two exposed ends still exist, but since the metal conductive layer is laid without passing through the exposed two end positions, but passing through the middle part of the U-shaped mouth, as shown in the figure Figure 13 The property of the insulating material of this part is relatively stable, which greatly improves the electrical isolation performance of the device.

[0066] The embodiment of the present application also provides a manufacturing method of a MEMS-based in-plane three-axis large displacement actuation platform and the MEMS-based in-plane three-axis large displacement actuation platform, comprising an outer frame 1, a cross island frame 2, a bidirectional comb-shaped driving unit 3, a long spring beam 4 and a short spring beam 5, and comprising the following steps:

[0067] Step one: etching of a glass substrate. The glass substrate is the support structure of the entire device.

[0068] First, prepare a 4-inch BF33 glass 81 with a thickness of 500 microns, as shown in Figure 8 a, after organic cleaning, spin coating of photoresist, and photoetching of the photoresist in a photoetching machine through a mask plate;

[0069] Step two: etching a 12 μm cavity by using a magnetic neutral loop discharge plasma (NLD) anisotropic etching technology, and removing the photoresist by wet method, as shown in Figure 7 、 8 b, the white part is the cavity formed by etching and removing the material;

[0070] Step three: prepare a 4-inch low-resistance silicon 82 (thickness 400 microns), as shown in Figure 8 c, the BF33 glass wafer with a cavity structure is bonded to the low-resistance silicon wafer by using an anodic bonding process;

[0071] Step four: thinning the low-resistance silicon wafer surface of the bonded wafer to 100 μm thick using a thinning machine, as shown in Figure 8 d. The low-resistance silicon 82 serves as the device layer.

[0072] Step five: deep silicon etching (DRIE) of the low-resistance silicon to form an independent part by cutting the stator from the low-resistance silicon, and then cutting the left and right comb-shaped arrays of the stator into two independent parts to achieve electrical isolation between the two, as shown in Figure 9 the figure shows that the etching of the electrical isolation channel is set at a certain position. In order to realize the electrical isolation of the two, and also to ensure that the two are an integral whole, avoid the left comb-shaped array from being suspended and falling off from the low-resistance silicon, the cut two also need to be bonded together. As shown in Figure 9As shown, the electrically isolated trenches under the left and right comb arrays are U-shaped. The reason for the U-shape is as described above and will not be repeated here. Similarly, the electrically isolated trenches at the junction of the right comb array and the low-resistance silicon are also U-shaped. The process is as follows: spin on photoresist, photoetch through a mask in a photoetch machine, etch the trenches in the low-resistance silicon wafer using deep reactive ion etching (DRIE), and then remove the photoresist.

[0073] Step six: fill the trenches with BCB material 83 to bond the left and right comb arrays together and to bond the right comb array to the low-resistance silicon 82, as shown in Figure 9 f. As shown in Figure 8 f, the BCB liquid is drawn into the trenches in the low-resistance silicon to serve as an insulating layer, and the BCB material is cured at high temperature. The BCB on the surface of the low-resistance silicon is removed by chemical mechanical polishing (CMP) to leave only the BCB in the trenches, as shown in Figure 9 f. The left and right comb arrays are bonded together by the BCB material to form a complete block. The right comb array is bonded to the low-resistance silicon by the BCB material to form a complete block. The BCB material is insulating and also ensures the electrical isolation of the left and right comb arrays and the electrical isolation of the right comb array from the entire low-resistance silicon wafer.

[0074] Step seven: deposit a PECVD oxide layer 84 on the low-resistance silicon, as shown in Figure 8 h. As shown in Figure 9 f, the three left comb arrays on the stator are already three independent electrically isolated plates and need to be interconnected with metal to become a conductive whole. When the metal layer is laid on the entire low-resistance silicon plate, it will pass through the three independent plates of the right comb arrays on the stator. Since the low-resistance silicon itself is conductive, the metal conductive layer laid on the low-resistance silicon plate needs to be electrically isolated from the right three comb arrays, so an oxide layer needs to be deposited as an insulating layer. First, the three left comb arrays of the stator are connected by laying an insulating layer on the low-resistance silicon plate, and then a conductive metal layer is laid on the insulating layer to electrically connect the three left comb arrays. At the same time, an insulating layer also needs to be laid for the three right comb arrays of the stator. The three right comb arrays are already complete independent blocks, but the electrical isolation process still needs to be completed.

[0075] Step eight: sputter a 400 nm metal layer and use the lift-off process to make a metal wire layer 85 to lay three circuits, one for the left comb array of the stator, one for the right comb array of the stator, and one for the comb array of the mover, as shown in Figure 14As shown, the three left comb arrays of the stator are electrically connected by the metal wire layer. Meanwhile, the three comb arrays on the right side are also laid with metal wire layer to form a separate circuit. Thus, three independent circuits are formed: (1) the comb array circuit of the mover, which is directly connected with the low resistance silicon; (2) the left comb array circuit of the stator; (3) the right comb array circuit of the stator. The metal layer of the left and right comb array of the stator is laid on the insulating layer PECVD oxide layer, and the comb array of the mover is integrated with the low resistance silicon, and the circuit can be directly led out on the low resistance silicon.

[0076] Step nine: low resistance silicon is etched by deep silicon etching (DRIE) process, as shown in Figure 8 j. Similarly, photoresist is first spin-coated, then photoetched in a photoetching machine through a mask plate, and low resistance silicon is etched by deep silicon etching (DRIE) to form the actuating structure of the device layer.

[0077] As shown in Figure 1 , the deep silicon etching (DRIE) process etches out the cross island frame, bidirectional comb driving unit 3, long spring beam 4 and short spring beam 5 at the same time. During the etching process, a number of process beams 9 are reserved, one end of the process beam is connected to the cross island frame, and the other end is connected to the outer frame.

[0078] The process beam has three functions. The first function is to improve the heat dissipation performance of the device in the deep silicon etching (DRIE) process, and to improve the etching yield of the device. In the process of manufacturing the suspended structure of the device, especially in deep silicon etching (DRIE), if the heat conduction structure is not properly designed or effective heat management is not performed, the photoresist may be pasted during the etching process, thereby affecting the integrity and function of the device. In the deep silicon etching (DRIE) process, the etching area is continuously removed by ion bombardment and chemical reaction. A large amount of heat is generated. The suspended structure is usually a region with a large cavity, and the heat cannot be effectively dissipated through the substrate to the heat dissipation system. In the conventional process, the silicon wafer itself can exchange heat with the tray or cooling system through the substrate to carry away the heat generated during etching. However, in the suspended structure etching, the heat cannot be effectively conducted to the heat dissipation system through the silicon substrate due to the cavity below the structure. If an effective heat conduction structure is not designed, the heat generated during etching cannot be discharged in time, causing the local temperature of the suspended structure to rise. When the temperature reaches the thermal stability limit of the photoresist, the photoresist will be denatured due to the high temperature, which is commonly known as pasting. The denatured photoresist loses its original etching resistance and cannot effectively shield the etching gas, thereby exposing the areas that should be protected, so that these areas are directly etched. In the case of pasting, the small structures (such as spring beams, cantilever beams, and other precision structures) that should be covered by the photoresist are exposed to the etching gas. The etching gas (such as SF6) in the DRIE process not only etches the silicon surface, but also erodes the exposed precision structures through physical and chemical reactions. These structures are often very fragile and delicate, and once exposed to a high-energy etching environment, the integrity of the structure may be compromised, resulting in device failure.

[0079] Through the design of the process beam, the cross-shaped island frame that was originally disconnected from the outer frame is connected through the process beam. The heat generated by the comb-shaped array during deep silicon etching is transmitted to the cross-shaped island frame through the long spring beam, and then transmitted to the outer frame through the process beam, improving the efficiency of heat dissipation and avoiding device failure caused by overheating.

[0080] The second function of the process beam is to enhance the structural strength of the device during transportation to prevent damage to the device caused by external forces during transportation. Suspended structures are usually fragile and can be damaged during transportation due to external environmental factors, thereby reducing product reliability and shipment yield.

[0081] The third function of the process beam is to improve the stability and reliability of the device structure when the image sensor is wire-bonded on the in-plane three-axis large displacement actuation platform. When sensitive devices such as CMOS are integrated onto the MEMS actuation platform, the instantaneous pressure generated during the wire-bonding process may cause structural damage to the suspended platform, thereby affecting device performance and yield. Currently, the solution to this problem is to separately add a process support structure under the device suspension structure, and then remove the process support structure after the wire-bonding process is completed. The process steps are complex (Design, fabrication and actuation of a MEMS based image stabilizer for photographic cell phone applications, Jin-Chern Chiou et al 2010 J. Micromech. Microeng. 20 075025). The present application provides sufficient support through the design of the process beam to ensure the structural integrity during the wire-bonding process, solves the balance problem between flexibility and rigidity of the suspended structure, and thus improves the application potential of the MEMS platform in high-integration devices. For example, in the case of optical image stabilization and other scenarios that require the integration of sensitive devices Figure 8 As shown in FIG. 10, after the CMOS image sensor is mounted on the MEMS platform, wire-bonding needs to be performed. Since the cross-shaped island frame is a suspended structure, it lacks support, and the instantaneous downward pressure applied during wire-bonding may damage the MEMS platform. At this time, the process beam can provide support to withstand the instantaneous pressure and prevent the platform from being damaged. Before wire-bonding is completed and the device is ready for use, the process beam can be removed by laser sintering to ensure the normal function and operation of the platform and not affect the final performance of the device.

[0082] In the description of the present application, it should be noted that the orientations or positional relationships indicated by the terms "up", "down", "left", "right", "clockwise" and "counterclockwise" are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0083] The above embodiments only illustrate the basic principles and characteristics of the present application, and the present application is not limited to the above embodiments. Without departing from the spirit and scope of the present application, various changes and modifications can be made to the present application, and these changes and modifications all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing a MEMS-based in-plane three-axis large displacement actuation platform, comprising an outer frame (1), a cross island frame (2), a bidirectional comb drive unit (3), a long spring beam (4), and a short spring beam (5); The outer frame (1) includes a cavity for accommodating the cross island frame (2) and a cavity for accommodating the bidirectional comb drive unit (3); The cross island frame (2) includes a cross (21) and crossbars (22), wherein there are four crossbars (22) respectively located at the outer ends of the cross (21); The bidirectional comb drive unit (3) is composed of a stator (31) and a mover (32). The stator (31) has an opening slot (40). The left side of the opening slot (40) has a first left-side comb array (41) and the right side has a first right-side comb array (42). The mover (32) has a rectangular protrusion (33). The left side of the rectangular protrusion has a second left-side comb array (34) and the right side has a second right-side comb array (35). The rectangular protrusion (33) is inserted into the middle of the opening slot (40). The first left-side comb array (41) and the second left-side comb array (34) intersect each other and have gaps. The first right-side comb array (42) and the second right-side comb array (35) intersect each other and have gaps. One end of the short spring beam (5) is connected to the mover (32), and the other end is connected to the stator (31); One end of the long spring beam (4) is connected to the mover (32), and the other end is connected to the cross island frame (2); There are four bidirectional comb drive units (3), which are located in the four quadrants of the cross island frame. Each bidirectional comb drive unit (3) is connected to the cross island frame (2) through a long spring beam (4). The four bidirectional comb drive units (3) are set at a 90-degree angle to each other. The manufacturing method includes the following steps: Step 1: Etching of the glass substrate; A BF33 glass sheet is organically cleaned and then spin-coated with photoresist. The photoresist is then photolithographically etched through a photomask inside the photolithography machine. Step 2: The cavity structure is etched using magnetic neutral loop discharge plasma (NLD) anisotropic etching technology, and the photoresist is removed by wet process; Step 3: Use an anodic bonding process to bond the side of the BF33 glass wafer with the cavity structure to the low-resistivity silicon wafer; Step 4: Use a thinning machine to thin the low-resistivity silicon wafer surface of the bonding wafer; Step 5: Deeply etch electrical isolation channels on low-resistivity silicon to cut the stator out of the low-resistivity silicon to form an independent part. Then cut the left and right comb arrays of the stator into two independent parts to achieve electrical isolation between them. After that, set the position to etch electrical isolation channels. The electrical isolation channels on the lower side of the left and right comb arrays are U-shaped. Step Six: Filling the electrical isolation channel with BCB material. The cut and separated left and right comb arrays are bonded together as a whole. Then, the right comb array is bonded to the low-resistivity silicon as a whole. Liquid BCB is vacuum-pumped into the isolation channel of the etched low-resistivity silicon as an insulating layer. The BCB material is cured at high temperature. The BCB on the surface of the low-resistivity silicon is removed by chemical mechanical polishing (CMP). Only the BCB material in the channel needs to be retained. Step 7: PECVD oxide layer is deposited on low-resistivity silicon, one channel of the left comb array and one channel of the right comb array; Step 8: Sputter metal layers and use a lift-off process to create metal conductor layers for laying three circuits: one comb array on the left side of the stator, one comb array on the right side of the stator, and one comb array on the mover. The metal layers of the comb arrays on the left and right sides of the stator are laid on the insulating PECVD oxide layer. The comb array on the mover is integrated with the entire low-resistivity silicon and the circuit is directly led out on the low-resistivity silicon. Step 9: Deep silicon etching process to etch low-resistivity silicon. First, spin-coat photoresist, then photolithography is performed in the photolithography machine through a mask. Deep silicon etching of low-resistivity silicon is performed, and at the same time, the cross island frame, bidirectional comb drive unit (3), long spring beam (4) and short spring beam (5), as well as several process beams (9) are etched. One end of the process beam (9) is connected to the cross island frame (2), and the other end is connected to the outer frame (1).

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