Variable-rigidity micromirror and scanning density modulation method

Abstract

The invention relates to the technical field of spinning processing, and particularly discloses a variable-rigidity micromirror and a scanning density modulation method.The variable-rigidity micromirror comprises a micromirror body, the micromirror body is composed of a micromirror plate body, a first shaft rod, a second shaft rod and an assembling component, the first shaft rod is fixedly connected to the interior of the micromirror plate body, and the second shaft rod is fixedly connected to the interior of the assembling component; one end of the first shaft rod is fixedly connected with one end of the assembling component, an aluminum layer material and a silicon dioxide layer material are selected as two materials of the Bimorph structure, and MEMS micromirror characteristic frequencies under different voltages can be obtained by changing the voltages at the two ends of a lead layer electrode to change the rigidity of a cantilever beam, so that the micromirror generates different deflection angles. Through the characteristic that shape memory layers such as resin and liquid crystal elastomers can deform after being heated, the memory material structure deforms and the rigidity of the cantilever beam is changed through the heat effect brought by pressurization, the scanning frequency can be controlled, and the problem that the scanning density cannot be modulated in the prior art is solved.

Description

Technical Field

[0001] The invention relates to the technical field of spinning processing, in particular to a variable rigidity micromirror and a scanning density modulation method. Background Art

[0002] MEMS micromirrors integrate reflectors and drivers through semiconductor micromachining technology. Their minimum size is usually in the micron level. They are an important research area of ​​micro-opto-electromechanical systems and are widely used in biomedical coherence tomography, optical switches, lidar and other fields.

[0003] At present, there are four driving modes for MEMS micromirrors: electrostatic driving, electromagnetic driving, piezoelectric driving and electrothermal driving. The disadvantage of electrothermal driving MEMS micromirrors is that they respond slowly after power is turned on, cannot meet the industrial demand for high scanning frequency and the scanning frequency cannot be changed; the disadvantage of electromagnetic driving is that an external magnetic field is required to drive the micromirror, which is technically difficult and cannot accurately control the change of scanning frequency. In high-order systems, it is easily affected by piezoelectric materials and electromagnetic interference and fails; piezoelectric driving is limited to piezoelectric materials and external voltage, and its actual displacement is limited, the reflection angle is small, cannot meet the large angle demand, and the scanning frequency is not variable; electrostatic driving can make the micromirror scan at a large angle and has a compact structure, but the required driving voltage is high. None of the above four driving modes can achieve variable density scanning. At a certain resonant frequency, it is difficult for MEMS micromirrors to achieve modulatable scanning field density and cannot be applied to a variety of application scenarios. If the scanning density is changed by changing the frequency of the fast and slow axes of the Lissajous scanning, the quality factor curve will change, and the scanning range of the Lissajous scanning at the same distance will change, which cannot meet the demand of only changing the scanning density.

[0004] To this end, we propose a variable stiffness micromirror and scanning density modulation method to solve the above problems. Summary of the invention

[0005] The object of the present invention is to provide a variable stiffness micromirror and a scanning density modulation method to solve the problems mentioned in the above background technology.

[0006] To achieve the above-mentioned object, the present invention provides a variable-rigidity micromirror, comprising a micromirror body, wherein the micromirror body is composed of a micromirror plate, a first shaft, a second shaft, and an assembly component, wherein the first shaft is fixedly connected to the inside of the micromirror plate, one end of the first shaft is fixedly connected to one end of the assembly component, the second shaft is fixedly connected to the inside of the assembly component, and a lens body is provided on a side of the assembly component away from the second shaft; The micromirror body is composed of a silicon wafer substrate, a silicon dioxide layer, a lead layer, a shape memory layer, and an aluminum layer. The silicon dioxide layer is arranged on the silicon wafer substrate, the lead layer is arranged on the silicon dioxide layer, the shape memory layer is arranged on the lead layer, and the aluminum layer is arranged on the silicon dioxide layer and located on the inner side of the lead layer.

[0007] In a further embodiment, a first circular groove is formed inside the micromirror plate body, and the assembly component is fixedly connected inside the first circular groove via a first shaft.

[0008] In a further embodiment, the assembly component includes a first ring, which is fixedly connected to the inside of the first circular groove via a first shaft, and a second ring is fixedly connected to the inside of the first ring via a second shaft, and the lens body is located inside the second ring.

[0009] In a further embodiment, a second circular groove is formed inside the first circular ring, and the second circular ring is fixedly connected to the inside of the second circular groove via a second shaft.

[0010] In a further embodiment, a third circular groove is formed inside the second circular ring, and the lens body is disposed inside the third circular groove.

[0011] A variable stiffness micromirror scanning density modulation method comprises the following steps: Step 1: First, a PECVD process is used to deposit a first layer of silicon dioxide with a thickness of 1-3 μm on a silicon wafer substrate, and then wet etching is used to form a pattern; Step 2: Using a sputtering process, a 0.1-0.5 μm layer of thermal resistor material lead is sputtered onto the surface of the silicon dioxide layer deposited in the above step. After the sputtering operation is completed, a pattern is formed by dry etching; Step 3: Use the PECVD process to deposit a 0.4 μm silicon dioxide layer as a protective layer and insulating layer for the lead layer of the thermal resistor, and then use dry etching to remove the silicon dioxide layer in the mirror area; Step 4: Sputter an aluminum layer with a thickness of 1-3 μm on the silicon dioxide insulating layer in step 1 by using a spin coating process, and then use dry etching to obtain the required pattern and form a mirror surface at the same time. Sputter a shape memory layer on the lead layer by using a spin coating process, and then use dry etching to obtain the required pattern. This step requires precise control of sputtering parameters, such as sputtering power, time, gas flow, etc., to ensure the uniformity and thickness of the shape memory layer, which is usually 0.1-0.5 μm. After sputtering, use dry etching technology to remove the shape memory layer in the non-pattern area to form the required pattern; Step 5: Plate an aluminum layer on the mirror structure as a reflective mirror. This step usually uses electroplating or evaporation technology to ensure that the aluminum layer is uniform, dense and has good reflective properties. The thickness of the aluminum plating should be determined according to specific needs, but it is generally controlled at around 0.1-0.5μm to balance reflectivity and cost; Step 6: Perform front etching to release the cantilever beam and mirror structure; Step 7: Perform deep silicon etching on the back side of the silicon wafer substrate, and perform a buried silicon dioxide layer etching step by reactive ion etching (RIE) to form a cavity under the mirror plate and the actuator.

[0012] The specific operation method of sputtering a shape memory layer on the surface of the lead layer in step 4 and plating aluminum as a reflective mirror in step 5 is as follows: Operation 1: Apply voltage 1-100V to the lead electrode, the lead electrode releases heat, the electrothermal structure / shape memory structure deforms, and the stiffness of the cantilever beam changes. When applying voltage to the lead electrode, a precise power controller should be used to ensure the stability and repeatability of the voltage. The voltage range is 1-100V and can be adjusted as needed to control the heat generation of the lead electrode and the degree of deformation of the electrothermal structure / shape memory structure. The degree of deformation will directly affect the stiffness of the cantilever beam.

[0013] Operation 2: The resonant frequency of the entire mirror structure is increased or decreased between 500-10000 Hz by changing the stiffness of the cantilever beam.

[0014] Operation three: Control the scanning density change within the range of 1-50 times. In addition to changing the resonant frequency by adjusting the stiffness of the cantilever beam, other mechanisms can also be combined, such as adjusting the driving signal of the scanning mirror, optimizing the scanning path, etc., to achieve dynamic adjustment of the scanning density. In addition, in order to verify the change in scanning density, high-precision measuring equipment such as laser interferometers can be used to monitor and analyze the scanning trajectory in real time.

[0015] Compared with the prior art, the present invention has the following beneficial effects: First, in the present invention, aluminum layer and silicon dioxide layer materials are selected as two materials of the Bimorph structure. By changing the voltage at both ends of the lead layer electrode to change the stiffness of the cantilever beam, the characteristic frequency of the MEMS micromirror under different voltages can be obtained to make the micromirror produce different deflection angles, thereby realizing an adjustable scanning field of view.

[0016] Secondly, in the present invention, ROI technology can reduce processing time, increase accuracy, optimize image processing efficiency, change the stiffness of the cantilever beam to achieve controllable scanning frequency, meet the high-precision imaging requirements of the ROI area, and provide feasibility for in-depth research on the ROI area.

[0017] Thirdly, in the present invention, the shape memory materials such as resins and liquid crystal elastomers are deformed by heat, and the thermal effect brought by pressure is used to deform the structure of the memory material, thereby changing the stiffness of the cantilever beam, thereby realizing the control of the scanning frequency, and solving the problem of the non-modulatable scanning density in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the dual-axis micromirror structure of the present invention; Figure 2 It is a schematic diagram of the middle layer structure of the present invention; Figure 3 Schematic diagram of the uniaxial micromirror structure in the present invention.

[0019] In the figure: 1. micromirror body; 111. silicon wafer substrate; 112. silicon dioxide layer; 113. lead layer; 114. shape memory layer; 115. aluminum layer; 2. first circular groove; 101. micromirror plate; 3. first shaft; 4. second shaft; 5. assembly component; 51. first circular ring; 52. second circular groove; 53. second circular ring; 54. third circular groove; 6. lens body. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] See also Figure 1-Figure 3In an embodiment of the present invention, a variable stiffness micromirror includes a micromirror body 1, wherein the micromirror body 1 is composed of a micromirror plate 101, a first shaft 3, a second shaft 4, and an assembly component 5, wherein the first shaft 3 is fixedly connected to the inside of the micromirror plate 101, one end of the first shaft 3 is fixedly connected to one end of the assembly component 5, the second shaft 4 is fixedly connected to the inside of the assembly component 5, and a lens body 6 is provided on a side of the assembly component 5 away from the second shaft 4, and the micromirror body 1 is composed of a silicon wafer substrate 111, a silicon dioxide layer 112, a lead layer 113, a shape memory layer 114, and an aluminum layer 115, wherein the silicon dioxide layer 112 is provided on the silicon wafer substrate 111, and the lead layer 113 is provided on the lead layer 114. 113 is arranged on the silicon dioxide layer 112, the shape memory layer 114 is arranged on the lead layer 113, the aluminum layer 115 is arranged on the silicon dioxide layer 112 and is located on the inner side of the lead layer 113, the micromirror surface is made of Ag, Si is selected for the surroundings and the lower end of the mirror surface, two cantilever beams with Bimorph structure are symmetrically connected at both ends, the lead layer 113 resistance layer is in the middle of the cantilever beam, and sufficient heat is provided for the cantilever beam drive, and the aluminum layer 115 and the silicon dioxide layer 112 with different expansion coefficients are respectively provided on both sides for the driver to provide deformation, and the aluminum layer 115 and the silicon dioxide layer 112 with two materials with large differences in expansion coefficients are selected as the two materials of the Bimorph structure, and the lead layer 113 is used as the electrode material The material is heated on both sides, and by changing the voltage at both ends of the lead layer 113 electrode, the difference in the thermal effect of the current is used to make the shape memory layer 114 produce different degrees of structural deformation to change the stiffness of the cantilever beam. The silicon dioxide layer 112 is used to block the lead layer 113 and the aluminum layer 115 to ensure that the variable stiffness micromirror can work stably. The cantilever beam is designed with a Bimorph structure, and an aluminum layer 115 metal elastic sheet is added between two silicon dioxide layers 112. The piezoelectric effect is used to make the upper and lower silicon dioxide layers 112 produce opposite deformations. Due to the constraint of the aluminum layer 115 metal elastic sheet, the entire Bimorph structure can bend or deflect, so as to achieve the purpose of changing the stiffness of the cantilever beam. Lissa The Lissajous scanning method modulates the horizontal and vertical scanning frequencies in the resonance mode to increase the greatest common factor of the dual-axis scanning frequency, slow down the scanning speed, and effectively realize high-density scanning of the ROI area; through improved design, the stiffness of the cantilever beam is changed to realize the modulation of the dual-axis scanning frequency, and then the Lissajous scanning frequency is controlled. The dual-axis scanning frequency is modulated in the ROI area to increase the greatest common divisor of the dual-axis scanning frequency, and a higher scanning density is obtained, so that the MEMS scanning micromirror can not only realize the basic function of the micromirror mirror deflection around the axis, but also change the stiffness of the cantilever beam and then change the characteristic frequency, realize the modulated scanning field density, enhance the performance of the micromirror, and have a wide range of application scenarios. And by adopting a polycrystalline structure, introducing materials such as resin and liquid crystal elastomer to control the change of the variable stiffness cantilever beam, the product has higher performance.

[0022] See also Figure 1 A first circular groove 2 is formed inside the micromirror plate 101 , and the assembly component 5 is fixedly connected to the inside of the first circular groove 2 via a first shaft 3 .

[0023] See also Figure 1 The assembly component 5 includes a first circular ring 51, which is fixedly connected to the inside of the first circular groove 2 through a first shaft 3, a second circular ring 53 is fixedly connected to the inside of the first circular ring 51 through a second shaft 4, the lens body 6 is located inside the second circular ring 53, a second circular groove 52 is opened inside the first circular ring 51, the second circular ring 53 is fixedly connected to the inside of the second circular groove 52 through a second shaft 4, a third circular groove 54 is opened inside the second circular ring 53, and the lens body 6 is arranged inside the third circular groove 54.

[0024] A variable stiffness micromirror scanning density modulation method comprises the following steps: Step 1: First, a first silicon dioxide layer 112 with a thickness of 1-3 μm is deposited on a silicon wafer substrate 111 using a PECVD process, and then a pattern is formed using wet etching; Step 2: Using a sputtering process, a 0.1-0.5 μm layer of thermal resistor material lead layer 113 is sputtered onto the surface of the silicon dioxide layer 112 deposited in the above step. After the sputtering operation is completed, a pattern is formed by dry etching; Step 3: Using the PECVD process, a 0.4 μm silicon dioxide layer 112 is deposited as a protective layer and an insulating layer for the thermal resistor lead layer 113, and then the silicon dioxide layer 112 in the mirror area is removed by dry etching; Step 4: Sputter an aluminum layer 115 with a thickness of 1-3 μm on the silicon dioxide layer 112 insulating layer in step 1 by using a spin coating process, and then use dry etching to obtain the required pattern and form a mirror surface at the same time. Sputter a shape memory layer 114 on the lead layer 113 by using a spin coating process, and then use dry etching to obtain the required pattern. This step requires precise control of sputtering parameters, such as sputtering power, time, gas flow, etc., to ensure the uniformity and thickness of the shape memory layer 114, which is usually 0.1-0.5 μm. After sputtering, use dry etching technology to remove the shape memory layer 114 in the non-pattern area to form the required pattern; Step 5: A layer of aluminum 115 is plated on the mirror structure as a reflective mirror. This step usually uses an electroplating or evaporation process to ensure that the aluminum layer 115 is uniform, dense and has good reflective properties. The thickness of the aluminum plating should be determined according to specific needs, but it is generally controlled at about 0.1-0.5μm to balance reflectivity and cost; Step 6: Perform front etching to release the cantilever beam and mirror structure; Step 7: Deep silicon etching is performed on the back side of the silicon wafer substrate 111, and a buried silicon dioxide layer 112 etching step is performed by a reactive ion etching (RIE) method to form a cavity under the mirror plate and the actuator.

[0025] The specific operation method of sputtering a shape memory layer 114 on the surface of the lead layer 113 in step 4 and plating aluminum as a reflective mirror in step 5 is as follows: Operation 1: Apply voltage 1-100V to the lead layer 113 electrode, the lead layer 113 electrode releases heat, the electrothermal structure / shape memory structure deforms, and the stiffness of the cantilever beam changes. When applying voltage to the lead layer 113 electrode, a precise power controller should be used to ensure the stability and repeatability of the voltage. The voltage range is 1-100V and can be adjusted as needed to control the heat generation of the lead layer 113 electrode and the degree of deformation of the electrothermal structure / shape memory structure. The degree of deformation will directly affect the stiffness of the cantilever beam.

[0026] Operation 2: The resonant frequency of the entire mirror structure is increased or decreased between 500-10000 Hz by changing the stiffness of the cantilever beam.

[0027] Operation three: Control the scanning density change within the range of 1-50 times. In addition to changing the resonant frequency by adjusting the stiffness of the cantilever beam, other mechanisms can also be combined, such as adjusting the driving signal of the scanning mirror, optimizing the scanning path, etc., to achieve dynamic adjustment of the scanning density. In addition, in order to verify the change in scanning density, high-precision measuring equipment such as laser interferometers can be used to monitor and analyze the scanning trajectory in real time.

[0028] The working principle of the present invention is as follows: a first silicon dioxide layer 112 with a thickness of 1-3 μm is deposited on a silicon wafer substrate 111, and then a pattern is formed by wet etching. A layer of a thermal resistor material lead layer 113 with a thickness of 0.1-0.5 μm is sputtered onto the surface of the silicon dioxide layer 112 deposited in the above step by using a sputtering process. A layer of a silicon dioxide layer 112 with a thickness of 0.4 μm is deposited by using a PECVD process as a protective layer and an insulating layer for the thermal resistor lead layer 113. Then, a dry etching process is used to form a pattern. The silicon dioxide layer 112 in the mirror area is removed by etching, and an aluminum layer 115 with a thickness of 1-3 μm is sputtered on the insulating layer of the silicon dioxide layer 112 in step 1 by a spin coating process, and then a required pattern is obtained by dry etching, and a mirror surface is formed at the same time, and a shape memory layer 114 is sputtered on the lead layer 113 by a spin coating process, and then a required pattern is obtained by dry etching, and an aluminum layer 115 is plated on the mirror structure as a reflective mirror surface; a voltage of 1-100V is applied to the lead layer 113 electrode, and the lead layer 11 3. The electrodes release heat, the electrothermal structure / shape memory structure deforms, and the stiffness of the cantilever beam changes. By changing the stiffness of the cantilever beam, the resonant frequency of the entire mirror structure increases or decreases between 500-10000 Hz, and the range of the change in the scanning density is controlled to be between 1 and 50 times. Therefore, by changing the voltage at both ends of the lead layer 113 electrodes to change the stiffness of the cantilever beam, the characteristic frequency of the MEMS micromirror under different voltages can be obtained, so that the micromirror produces different deflection angles, and an adjustable scanning field of view can be achieved. The ROI technology can reduce processing time, increase accuracy, and optimize image processing efficiency. Changing the stiffness of the cantilever beam can achieve controllable scanning frequency, which can meet the high-precision imaging requirements of the ROI area and provide feasibility for in-depth research on the ROI area. Through the heat-deformable characteristics of shape memory materials such as resins and liquid crystal elastomers, the thermal effect brought by pressurization causes the structure of the memory material to deform, and the stiffness of the cantilever beam is changed, so that the scanning frequency can be controlled, solving the problem of non-modulatable scanning density in the prior art.

[0029] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0030] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A variable stiffness micromirror, characterized in that: The micromirror body (1) comprises a micromirror plate (101), a first shaft (3), a second shaft (4), and an assembly component (5), wherein the first shaft (3) is fixedly connected to the inside of the micromirror plate (101), one end of the first shaft (3) is fixedly connected to one end of the assembly component (5), the second shaft (4) is fixedly connected to the inside of the assembly component (5), and a lens body (6) is provided on a side of the assembly component (5) away from the second shaft (4); The micromirror body (1) is composed of a silicon wafer substrate (111), a silicon dioxide layer (112), a lead layer (113), a shape memory layer (114), and an aluminum layer (115); the silicon dioxide layer (112) is arranged on the silicon wafer substrate (111), the lead layer (113) is arranged on the silicon dioxide layer (112), the shape memory layer (114) is arranged on the lead layer (113), and the aluminum layer (115) is arranged on the silicon dioxide layer (112) and is located on the inner side of the lead layer (113).

2. A variable stiffness micromirror according to claim 1, characterized in that: A first circular groove (2) is provided inside the micromirror plate body (101), and the assembly component (5) is fixedly connected to the inside of the first circular groove (2) via a first shaft (3).

3. A variable stiffness micromirror according to claim 2, characterized in that: The assembly component (5) comprises a first circular ring (51), the first circular ring (51) being fixedly connected to the inside of a first circular groove (2) via a first shaft (3), a second circular ring (53) being fixedly connected to the inside of the first circular ring (51) via a second shaft (4), and the lens body (6) being located inside the second circular ring (53).

4. A variable stiffness micromirror according to claim 3, characterized in that: A second circular groove (52) is formed inside the first circular ring (51), and the second circular ring (53) is fixedly connected to the inside of the second circular groove (52) via a second shaft (4).

5. A variable stiffness micromirror according to claim 4, characterized in that: A third circular groove (54) is provided inside the second circular ring (53), and the lens body (6) is arranged inside the third circular groove (54).

6. A variable stiffness micromirror scanning density modulation method, characterized in that: The usage steps include the following: Step 1: firstly, a first silicon dioxide layer (112) with a thickness of 1-3 μm is deposited on a silicon wafer substrate (111) using a PECVD process, and then a pattern is formed using a wet etching method; Step 2: using a sputtering process to sputter a 0.1-0.5 μm layer of thermal resistor material lead (113) onto the surface of the silicon dioxide layer (112) deposited in the above step, and after the sputtering operation is completed, using dry etching to form a pattern; Step 3: using a PECVD process, a 0.4 μm silicon dioxide layer (112) is deposited as a protective layer and an insulating layer of the thermal resistor lead layer (113), and then dry etching is used to remove the silicon dioxide layer (112) in the mirror area; Step 4: using a spin coating process to sputter an aluminum layer (115) with a thickness of 1-3 μm on the insulating layer of the silicon dioxide layer (112) in step 1, and then using dry etching to obtain a desired pattern and simultaneously forming a mirror surface, and using a spin coating process to sputter a shape memory layer (114) on the lead layer (113), and then using dry etching to obtain a desired pattern; Step 5: coating a layer of aluminum (115) on the mirror structure as a reflective mirror; Step 6: Perform front etching to release the cantilever beam and mirror structure; Step 7: Perform deep silicon etching on the back side of the silicon wafer substrate (111), and perform a buried silicon dioxide layer (112) etching step by a reactive ion etching (RIE) method to form a cavity under the mirror plate and the actuator.

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