CN111204701A - Micromirror with fully-symmetrical differential capacitor angle feedback - Google Patents

Micromirror with fully-symmetrical differential capacitor angle feedback Download PDF

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CN111204701A
CN111204701A CN202010021829.5A CN202010021829A CN111204701A CN 111204701 A CN111204701 A CN 111204701A CN 202010021829 A CN202010021829 A CN 202010021829A CN 111204701 A CN111204701 A CN 111204701A
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fixed
layer
capacitor
insulating layer
silicon wafer
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CN111204701B (en
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李欢欢
白民宇
郭迪
李晓晓
马力
彭磊
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Xi'an Chishine Optoelectronics Technology Co ltd
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Xi'an Chishine Optoelectronics Technology Co ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
    • B81B7/0006—Interconnects
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
    • B81B7/0032—Packages or encapsulation
    • B81B7/007—Interconnections between the MEMS and external electrical signals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
    • B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
    • B81C1/00015—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems
    • B81C1/00261—Processes for packaging MEMS devices
    • B81C1/00301—Connecting electric signal lines from the MEMS device with external electrical signal lines, e.g. through vias
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
    • G02B26/0816—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements
    • G02B26/0833—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD
    • G02B26/0841—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD the reflecting element being moved or deformed by electrostatic means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B81—MICROSTRUCTURAL TECHNOLOGY
    • B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
    • B81B2201/00—Specific applications of microelectromechanical systems
    • B81B2201/02—Sensors

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  • Microelectronics & Electronic Packaging (AREA)
  • Manufacturing & Machinery (AREA)
  • Computer Hardware Design (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Micromachines (AREA)

Abstract

The invention relates to the field of micro-nano optical devices, in particular to a micro mirror with fully-symmetrical differential capacitance angle feedback, which comprises a base, wherein a first insulating layer is arranged on the upper surface of the base, a first fixing layer is arranged on the upper surface of the first insulating layer, a second insulating layer is arranged on the upper surface of the first fixing layer, a reflecting element layer is arranged on the upper surface of the second insulating layer, a third insulating layer is arranged on the upper surface of the reflecting element layer, a second fixing layer is arranged on the upper surface of the third insulating layer, a fourth insulating layer is arranged on the upper surface of the second fixing layer, and a bonding pad is arranged on the fourth insulating layer. The angle sensor is integrated in the micro mirror, so that the structure is compact, the power consumption is low, and the process compatibility is high; the structure has vertical and plane symmetry simultaneously, the driving is reliable and easy, the detection signal-to-noise ratio is high, and the complexity of a detection signal processing circuit is obviously reduced; can be suitable for application requirements from low frequency to high frequency.

Description

Micromirror with fully-symmetrical differential capacitor angle feedback
Technical Field
The invention relates to the field of micro-nano optical devices, in particular to a micro mirror with fully symmetrical differential capacitance angle feedback.
Background
The micro mirror is a micro-nano chip capable of effectively realizing light path regulation and is widely applied to the fields of projection, imaging, laser navigation and the like. The most widely used micromirrors include electrostatic, electromagnetic, piezoelectric, and electrothermal. Most of the prior micro mirrors adopt an open-loop control mode without angle feedback, and the micro mirror has the serious defect of lacking effective angle feedback to cause the problem of inaccurate control of the micro mirror, thereby causing the problems of projection and imaging drift, navigation deviation and the like. The prior partial micromirror adopts a certain angle feedback, but still has more problems.
In the currently used micromirror, an angle feedback method is to arrange an angle detection device outside the micromirror to measure the rotation angle of the micromirror, so that the angle feedback of the micromirror can be realized to a certain extent. For example, patent No. ZL 200410085274.1 discloses a micromirror solution for angle measurement using optical components. However, in the detection device of the method, components such as a laser light source, a light path, a position sensor and the like need to be added into the micro-mirror module, so that the volume, the power consumption and the system complexity of the micro-mirror module are greatly increased. More importantly, due to factors such as installation errors, the detection method is difficult to realize accurate angle feedback, and the consistency of each micro mirror module is poor.
There are also angle sensors integrated in the micromirrors for angle detection, for example, a micromirror with electrothermal drive and plate capacitance detection is disclosed in the patent application publication No. CN 109814251A. According to the scheme, a capacitor plate is arranged on a substrate, and the relation between the capacitance value on the capacitor plate and the actual torsion angle of the micro lens is used as a feedback value to perform signal feedback on a controller. The proposal reduces the components of the light path and the position sensor in the micro mirror module, and reduces the complexity of the micro mirror module to a certain extent. However, in the scheme, the flat electrode element is used as the angle feedback capacitor, the output of the feedback capacitor and the rotation angle of the micromirror have a nonlinear relation, the corresponding relation is complex, the output conversion speed is slow, the solution truncation error of the nonlinear relation is large, the flat electrode capacitor is small, the output signal is weak, the requirement on a processing circuit is high, and the signal-to-noise ratio is low. The proposal adopts an electrothermal driving mode, the working frequency of the micro mirror is low, and the micro mirror is difficult to be suitable for high-frequency scanning.
A piezoelectric driven Micromirror Integrated with a piezoelectric angle sensor is disclosed in the paper "piezoelectric Actuated mirror Integrated with Angle Sensors" (Key Engineering Materials 2011, 483:437 442). However, the piezoelectric driving and piezoelectric sensors are made of PZT materials, so that the process compatibility is poor, the processing difficulty is high, and the chip production line is easily polluted. Meanwhile, the piezoelectric sensor has extremely high requirements on the input impedance of a processing circuit, the circuit is complex, and the cost is high. Piezoelectric transducers have poor performance at low frequencies and are difficult to adapt for low frequency scanning of the micromirror.
The document 4-CN 107976871A-a dynamic deformation controllable micromirror mirror surface comb tooth structure and a processing method thereof, discloses a micromirror comb tooth processing method and a corresponding comb tooth structure electrostatic driving micromirror, can realize integrated micromirror angle detection, but the driving structure in the scheme has no symmetry, so the electrostatic driving control difficulty is large, and the control precision is low; more importantly, the detection structure has no symmetry, cannot realize fully differential detection output, has low signal-to-noise ratio of detection signals, low sensitivity and high requirement on a processing circuit, and is not beneficial to the improvement of control precision. Meanwhile, the processing method of the micro-mirror comb tooth structure proposed by the document needs to perform photoetching after etching the deep groove structure, i.e. high-quality glue homogenizing needs to be performed on the surface of the deep groove structure, and complete equal-thickness covering of a glue layer is ensured, which is extremely difficult to realize in process.
In summary, the micromirror without feedback has poor control accuracy, and the angle measurement scheme of the conventional micromirror with angle feedback has the problems of complex system, low signal-to-noise ratio, incapability of being simultaneously applicable to high frequency and low frequency, incapability of realizing static scanning, poor process compatibility and the like.
Disclosure of Invention
The invention provides a micromirror with fully symmetric differential capacitor angle feedback, aiming at the problems that the existing micromirror without feedback has poor control precision, and the angle measurement scheme of the micromirror with angle feedback has the defects of complex system, low signal-to-noise ratio, incapability of being simultaneously suitable for high frequency and low frequency, poor process compatibility and the like.
The realization process of the invention is as follows:
the utility model provides a micro mirror that possesses complete symmetry formula differential capacitance angle feedback, includes the base, the base upper surface is provided with the first insulating layer, the upper surface on first insulating layer is provided with first fixed layer, the upper surface on first fixed layer is provided with the second insulating layer, the upper surface on second insulating layer is provided with the reflection component layer, the upper surface on reflection component layer is provided with the third insulating layer, the upper surface on third insulating layer is provided with the second fixed layer, the upper surface on second fixed layer is provided with the fourth insulating layer, be provided with the pad on the fourth insulating layer.
Further, the base is the cavity frame column structure that the frame encloses all around, first insulating layer, first fixed layer, second insulating layer, reflection element layer, third insulating layer, second fixed layer, fourth insulating layer all superpose fixedly on the cavity frame column structure of base according to the order.
Furthermore, the first insulating layer, the second insulating layer, the reflecting element layer, the third insulating layer and the fourth insulating layer are all of a planar structure; the first fixed layer and the second fixed layer are of a ladder-shaped structure.
Furthermore, the first insulating layer is composed of a plurality of insulating thin layers arranged on the upper surface of the periphery of the hollow frame-shaped structure of the base; the first fixed layer comprises a first peripheral fixed structure, a first fixed capacitor, a second fixed capacitor, a third fixed capacitor, a fourth fixed capacitor, a first fixed driving element and a second fixed driving element; a first fixed capacitor, a second fixed capacitor, a third fixed capacitor and a fourth fixed capacitor are arranged on the inner sides of the two axial ends of the first peripheral fixed structure; a first fixed driving element and a second fixed driving element are arranged on the inner sides of the two radial ends of the first peripheral fixing structure; the first fixed capacitor, the second fixed capacitor, the third fixed capacitor, the fourth fixed capacitor, the first fixed driving element and the second fixed driving element are all suspended comb tooth structures, and the roots of the comb tooth structures are all connected with the first peripheral fixed structure; the lower surface of the comb teeth part is flush with the lower surface of the first peripheral fixed structure, and the upper surface of the comb teeth part exceeds the upper surface of the first peripheral fixed structure to form a stepped structure; the first peripheral fixing structure is connected with the first insulating layer.
Further, the second insulating layer is composed of a plurality of insulating thin layers arranged on the upper surface of the first peripheral fixing structure; the reflecting element layer comprises a reflecting mirror peripheral fixing structure, a mirror body, a first rotating capacitor, a second rotating capacitor, a third rotating capacitor, a fourth rotating capacitor, a first rotating driving element and a second rotating driving element; the first rotating capacitor, the second rotating capacitor, the third rotating capacitor, the fourth rotating capacitor, the first rotating driving element and the second rotating driving element are all suspended comb tooth structures; the axial both sides limit of the mirror body is connected with the peripheral fixed knot of speculum axial both sides limit inboard through first pivot, second pivot, the radial both sides limit of the mirror body is connected with the broach root of first rotation drive element, second rotation drive element respectively, first pivot both sides limit is connected with the broach root of first rotation capacitance, second rotation capacitance respectively, second pivot both sides limit is connected with the third rotation capacitance, fourth rotation capacitance's broach root respectively, the peripheral fixed knot of speculum constructs and is connected with the second insulating layer.
Further, the third insulating layer is composed of a plurality of insulating thin layers arranged on the upper surface of the reflector periphery fixing structure; the second fixed layer comprises a second peripheral fixed structure, a fifth fixed capacitor, a sixth fixed capacitor, a seventh fixed capacitor, an eighth fixed capacitor, a third fixed driving element and a fourth fixed driving element; a fifth fixed capacitor, a sixth fixed capacitor, a seventh fixed capacitor and an eighth fixed capacitor are arranged on the inner sides of the two axial ends of the second peripheral fixed structure; a third fixed driving element and a fourth fixed driving element are arranged on the inner sides of the two radial ends of the second peripheral fixed structure; the fifth fixed capacitor, the sixth fixed capacitor, the seventh fixed capacitor, the eighth fixed capacitor, the third fixed driving element and the fourth fixed driving element are all suspended comb tooth structures, and the roots of the comb tooth structures are all connected with a second peripheral fixed structure; the upper surface of the comb teeth part is flush with the upper surface of the second peripheral fixing structure, and the lower surface of the comb teeth part exceeds the lower surface of the second peripheral fixing structure to form a stepped structure; the second peripheral fixing structure is connected with the third insulating layer; the fourth insulating layer is composed of a plurality of insulating thin layers arranged on the upper surface of the second peripheral fixing structure.
Further, the first fixed driving element, the first rotating driving element and the third fixed driving element form a group of comb tooth driving capacitors; the second fixed driving element, the second rotating driving element and the fourth fixed driving element form a group of comb tooth driving capacitors; the first fixed capacitor and the first rotating capacitor form a group of comb tooth detection capacitors, and the fifth fixed capacitor and the first rotating capacitor form a group of comb tooth detection capacitors; the second fixed capacitor and the second rotating capacitor form a group of comb detection capacitors, and the sixth fixed capacitor and the second rotating capacitor form a group of comb detection capacitors; the third fixed capacitor and the third rotating capacitor form a group of comb detection capacitors, and the seventh fixed capacitor and the third rotating capacitor form a group of comb detection capacitors; the fourth fixed capacitor and the fourth rotating capacitor form a group of comb detection capacitors, and the eighth fixed capacitor and the fourth rotating capacitor form a group of comb detection capacitors; the comb tooth driving capacitor sets are arranged in a symmetrical structure; the comb detection capacitor bank is arranged in a symmetrical structure.
Furthermore, the base and the first insulating layer, the first insulating layer and the first fixed layer, the first fixed layer and the second insulating layer, the second insulating layer and the reflective element layer, the reflective element layer and the third insulating layer, the third insulating layer and the second fixed layer, and the second fixed layer and the fourth insulating layer are connected in a bonding mode; the base can be a hollow frame structure with a round, oval, diamond, rectangle or square shape.
Furthermore, the base, the first fixed layer and the second fixed layer are made of any one of monocrystalline silicon, polycrystalline silicon and amorphous silicon; the material of the reflecting element layer is selected from any one of monocrystalline silicon, polycrystalline silicon, amorphous silicon or high molecular polymer; the resistivity of the first fixed layer, the resistivity of the reflecting element layer and the resistivity of the second fixed layer are all less than 1 omega cm; the first insulating layer, the second insulating layer, the third insulating layer and the fourth insulating layer are made of any one of silicon oxide, silicon nitride, silicon carbide or high molecular polymer; the resistivities of the first insulating layer, the second insulating layer, the third insulating layer and the fourth insulating layer are all larger than 10 omega cm.
Further, the high molecular polymer is selected from any one of polydimethylsiloxane, SU8 glue, epoxy resin, polyamide, polyimide, polypropylene, polyethylene, polyvinyl chloride, polystyrene, polyethylene terephthalate and polymethyl methacrylate.
The manufacturing method of the micromirror with the fully symmetrical differential capacitance angle feedback comprises the following steps: (1) preparing a silicon wafer; (2) carrying out front-side first photoetching; (3) carrying out first dry etching on the front surface; (4) carrying out back surface first photoetching; (5) carrying out first dry etching on the back; (6) front oxygen ion implantation; (7) back oxygen ion implantation; (8) thinning and polishing the front side; (9) thinning and polishing the back; (10) carrying out second photoetching on the front surface; (11) carrying out second dry etching on the front surface; (12) carrying out secondary photoetching on the back surface; (13) carrying out secondary dry etching on the back; (14) preparing a base; (15) bonding the base with the silicon wafer subjected to the second dry etching on the back surface in the step 13; (16) releasing the structure; (17) preparing a front oxide layer; (18) and manufacturing a bonding pad.
The manufacturing method of the micromirror with the fully symmetric differential capacitance angle feedback more specifically comprises the following steps:
(1) preparing a silicon wafer, wherein the silicon wafer is monocrystalline silicon or polycrystalline silicon, the double surfaces of the silicon wafer are polished, the thickness of the silicon wafer is 50-300 mu m, and the resistivity of the silicon wafer is less than 0.01 omega cm;
(2) performing front-surface first photoetching to define a corresponding graph with the position of the front-surface oxygen ion implantation area changed in the vertical direction;
(3) the front side is etched by a dry method for the first time, and a groove-shaped structure is etched on the front side of the silicon wafer and used for subsequent oxygen ion implantation to realize the position change of the oxygen ion implantation in the vertical direction; removing the photoresist on the front side of the silicon wafer after the dry etching is finished; the depth of the groove-shaped structure realized in the step is 10nm-10 mu m;
(4) carrying out back first photoetching, namely reversing the silicon wafer, carrying out photoetching on the back, wherein the mask plate graph is a mirror image of the mask plate graph used for the front first photoetching, and defining a corresponding graph with the back oxygen ion implantation area changed in the vertical direction;
(5) the first dry etching is carried out on the back, and a groove-shaped structure is etched on the back of the silicon wafer and used for subsequent oxygen ion implantation to realize the position change of the oxygen ion implantation in the vertical direction; removing the photoresist on the back surface of the silicon wafer after the dry etching is finished, wherein the back groove-shaped structure realized in the step is symmetrical with the front groove-shaped structure realized in the step (3) about the neutral layer of the silicon wafer; the depth of the back groove-shaped structure realized in the step is 10nm-10 mu m;
(6) performing oxygen ion implantation on the front surface of the silicon wafer, and selecting proper implantation energy according to the required oxygen ion depth; forming an oxide layer at a position with a certain distance from the surface of the front side of the silicon wafer after oxygen ion implantation; the distance between the oxide layer and the front surface of the silicon wafer is different when the injection energy is different, the lower the energy is, the smaller the distance is, the larger the energy is, and the larger the distance is; because the dry etching is carried out in the step (3), a groove-shaped structure is formed on the front surface of the silicon wafer before oxygen ion implantation, namely the front surface of the silicon wafer is not a plane but has high and low undulations, in the same oxygen ion implantation, although the implantation energy is constant, the distance between the oxide layer and the front surface of the silicon wafer is the same, the oxide layer formed by implantation is not a plane but has the undulations in the vertical direction corresponding to the undulations of the front surface of the silicon wafer because the front surface of the silicon wafer has the high and low undulations; the implantation depth of the oxygen ions on the front surface is 5-100 μm;
(7) back oxygen ion implantation, wherein the back of the silicon wafer is subjected to integral oxygen ion implantation, and proper implantation energy is selected according to the required oxygen ion depth; forming an oxide layer at a position away from the surface of the back of the silicon wafer by a certain distance after oxygen ion implantation; the distance between the oxide layer and the back surface of the silicon wafer is different when the injection energy is different, the lower the energy is, the smaller the distance is, the larger the energy is, and the larger the distance is; because the dry etching is carried out in the step (3), a groove-shaped structure is formed on the surface of the back surface of the silicon wafer before the oxygen ion implantation, namely the surface of the back surface of the silicon wafer is not a plane but has the height fluctuation, in the same oxygen ion implantation, although the implantation energy is constant, the distance between the oxide layer and the surface of the back surface of the silicon wafer is the same, the oxide layer formed by the implantation is not a plane but has the fluctuation in the vertical direction corresponding to the fluctuation of the surface of the back surface of the silicon wafer because the surface of the back surface of the silicon wafer has the height fluctuation. The implantation depth of the back oxygen ions is equal to that of the front oxygen ions in the step (6);
(8) thinning and polishing the front surface, removing the groove-shaped structure used for assisting oxygen ion implantation on the front surface, and recovering the polished surface of the front surface;
(9) back thinning and polishing, namely removing the groove-shaped structure used for assisting oxygen ion implantation on the back surface and recovering the polished surface of the back surface; after the process of the step is finished, the silicon wafer forms a five-layer structure which comprises a first fixed layer, a second insulating layer, a reflector element layer, a third insulating layer and a second fixed layer from bottom to top; wherein the reflector element layer is of a planar structure and has a thickness of 5-100 μm, and the first and second fixed layers are of a stepped structure and have a thickness of 5-100 μm; the first and second pinned layers are symmetric about a mirror element layer center plane; the thicknesses of the second insulating layer and the third insulating layer are equal and are both 0.2-5 mu m, and the two insulating layers are symmetrical about the central plane of the reflector element layer;
(10) performing second photoetching on the front surface, and defining graphs corresponding to a third fixed driving element, a fourth fixed driving element, a fifth fixed capacitor, a sixth fixed capacitor, a seventh fixed capacitor and an eighth fixed capacitor of a second fixed layer;
(11) performing second dry etching on the front surface to etch a third fixed driving element, a fourth fixed driving element, a fifth fixed capacitor, a sixth fixed capacitor, a seventh fixed capacitor and an eighth fixed capacitor structure; removing the photoresist on the front side of the silicon wafer after etching; the etching depth is equal to the implantation depth of the front oxygen ions in the step (6);
(12) performing back-side second photoetching, namely reversing the silicon wafer, performing photoetching on the back side of the silicon wafer, and defining graphs corresponding to a first fixed driving element, a second fixed driving element, a first fixed capacitor, a second fixed capacitor, a third fixed capacitor and a fourth fixed capacitor;
(13) performing dry etching on the back surface for the second time to etch a first fixed driving element, a second fixed driving element, a first fixed capacitor, a second fixed capacitor, a third fixed capacitor and a fourth fixed capacitor structure; removing the photoresist on the back of the silicon wafer after etching; the etching depth is equal to the back oxygen ion implantation depth in the step 7;
(14) preparing a base by using monocrystalline silicon wafers or polycrystalline silicon wafers, wherein the resistivity is greater than 0.1 omega cm and the thickness is 100-800 mu m; firstly, depositing or thermally oxidizing the surface of a monocrystalline silicon wafer or a polycrystalline silicon wafer used for preparing a base to form an oxide layer serving as a first insulating layer, wherein the thickness of the oxide layer is 0.2-5 microns; manufacturing a base with a frame-shaped structure by adopting a dry etching or wet etching method;
(15) bonding the base with the silicon wafer finished in the step 13 (back surface second dry etching); the upper surface of the base is contacted with the lower surface of the silicon wafer finished in the step 13 during bonding, and the hollow area of the frame-shaped structure of the base is larger than the areas of the silicon wafer finished in the step 13 corresponding to the first fixed driving element, the second fixed driving element, the first fixed capacitor, the second fixed capacitor, the third fixed capacitor and the fourth fixed capacitor, so that the bonding alignment requirement is low, only the alignment tolerance of plus and minus 1-50 μm is required to be ensured, and the specific tolerance is determined according to the size of a specific device;
(16) releasing the structure, namely putting the bonded silicon wafer into a hydrofluoric acid wet etching groove or hydrogen fluoride dry releasing equipment, and etching to remove the two oxide layers formed in the step (6) and the step (7), so that the release of the structures contained in the first fixed layer, the reflector element layer and the second fixed layer is realized;
(17) preparing a front oxide layer, namely depositing a silicon oxide layer on the upper surface of the silicon chip after the structure in the step (16) is released, or preparing the oxide layer by a thermal oxidation method to be used as a fourth insulating layer; the thickness of the fourth insulating layer is 0.2-5 μm;
(18) and (4) manufacturing the bonding pad, namely manufacturing the bonding pad by adopting a sputtering or evaporation mode after the structure is manufactured, wherein the used mask is a hard mask.
The alternating drive signal used by the micromirror with the fully symmetric differential capacitor angle feedback of the present invention is selected from square wave, sawtooth wave, triangular wave, sine wave or cosine wave.
The driving structure of the micromirror with the fully-symmetrical differential capacitance angle feedback has symmetry in the vertical direction, and the comb teeth of the fixed driving element and the rotary driving element have height difference in the vertical direction, so that torque can be generated after driving voltage is applied, and parameter excitation is not needed; the driving structure has plane symmetry, so the driving force is symmetrical, and the control precision of the micromirror vibration is high. The detection structure has vertical and plane symmetry simultaneously, the detection signal is differential output, the detection output signal is strong, the signal-to-noise ratio is high, and the requirement of a processing circuit along with the detection signal is low. The specific driving and detecting principles are as follows:
the first and fourth fixed driving elements apply a driving voltage Vd1, the second and third fixed driving elements apply a driving voltage Vd2, and the first and second rotary driving elements are grounded. The fourth rotating capacitor, the second rotating capacitor, the third rotating capacitor and the fourth rotating capacitor are all grounded. The mirror element generates rotational vibration about the axis of rotation under the influence of electrostatic forces. The Vd1 and the Vd2 are square wave signals which are opposite in phase, the minimum value of the two square wave signals is 0, and the amplitude is Vd. When Vd1 is Vd, the mirror element rotation direction is defined as the forward direction, at which time the output values δ C1, δ C3, δ C6, and δ C8 of the first fixed capacitance, the third fixed capacitance, the sixth fixed capacitance, and the eighth fixed capacitance increase, and the output values δ C2, δ C4, δ C5, and δ C7 of the second fixed capacitance, the fourth fixed capacitance, the fifth fixed capacitance, and the seventh fixed capacitance decrease. Due to structural symmetry, δ C1- δ C3- δ C6- δ C8- δ C2- δ C4- δ C5- δ C7- δ C, and the total detected capacitance variation Δ C (δ C1+ δ C3+ δ C6+ δ C8) - (- δ C2- δ C4- δ C5- δ C7) -8 δ C (θ) are output in a differential mode. When Vd2 is Vd, the mirror element rotation direction is defined as the negative direction, at which time the output values δ C1, δ C3, δ C6, and δ C8 of the first fixed capacitance, the third fixed capacitance, the sixth fixed capacitance, and the eighth fixed capacitance decrease, and the output values δ C2, δ C4, δ C5, and δ C7 of the second fixed capacitance, the fourth fixed capacitance, the fifth fixed capacitance, and the seventh fixed capacitance increase. Due to structural symmetry, - δ C1 ═ δ C3 ═ δ C6 ═ δ C8 ═ δ C2 ═ δ C4 ═ δ C5 ═ δ C7 ═ δ C, the total detected capacitance variation Δ C is (δ C2+ δ C4+ δ C5+ δ C7) - (- δ C1- δ C3- δ C6- δ C8) ═ 8 δ C ═ f (θ) in the same differential output manner.
The total detected capacitance change Δ C is a function of the mirror element rotation angle θ, Δ C is introduced into the drive signals Vd1 and Vd2 as real-time angle feedback, and the drive signals Vd1 and Vd2 are adjusted in real-time.
The micromirror is driven by static electricity, and the capacitive sensor is used for angle feedback to form closed-loop control, so that the control precision of the micromirror is improved. The angle sensor is integrated in the micro mirror, so that the micro mirror is compact in structure, low in power consumption and high in process compatibility; the structure has vertical and plane symmetry simultaneously, the driving is reliable and easy, the detection signal-to-noise ratio is high, and the complexity of a detection signal processing circuit is obviously reduced; can be suitable for application requirements from low frequency to high frequency.
The bonding connection mode of the invention adopts normal temperature bonding (morning, Wangte, wai Zuan, Wang Yuan, Tianyanhong. wafer direct bonding and room temperature bonding technology research progress [ J ]. precision forming engineering 2018.10(1):67-73) if the used material is a high molecular material; if the material is inorganic material, all bonding methods and anodic bonding methods (Chendaming, Huli, Cheng Rong, Ben Si-glass-Si anodic bonding mechanism and mechanical property [ J ]. welding bulletin, 2019,40(02):123 + 127+166.) in the reference (Wang Chenxi, Wang Tet, wai Yuan, Tian Yan Red. wafer direct bonding and Room temperature bonding technology research progress [ J ]. precision forming engineering 2018.10(1):67-73) are adopted.
The invention has the following positive effects:
(1) the angle sensor is integrated in the micro-mirror to detect the real-time angle of the micro-mirror, so that the control precision of the micro-mirror is effectively improved.
(2) The integrated design of the micro mirror and the angle sensor, and the micro mirror and the sensor are contained in one chip, so that the structure is compact, the size is small, and the power consumption is low.
(3) The chip containing the micro-mirror and the sensor is manufactured by adopting a micro-nano manufacturing process primary flow sheet, the process compatibility is high, the structural and functional consistency and stability of the micro-mirror are high, and the subsequent packaging is simple.
(4) The angle sensor adopts a completely symmetrical capacitive sensor design, realizes differential output of the sensor, has large output signal, effectively inhibits noise, has high angle detection sensitivity and has low requirement on a subsequent processing circuit.
(5) The micromirror driving structure adopts a completely symmetrical design, and the rotating capacitor and the static capacitor have an initial vertical position difference, so that the problem that the driving of the plane micromirror structure is easy to start is avoided, and the micromirror driving structure can be applied to static scanning and dynamic scanning, and has wide application range and high control precision.
(6) The design of the electrostatic driving and capacitance type detection sensor ensures that the micro mirror can meet the scanning requirement from low frequency to high frequency.
(7) The method for manufacturing the micro mirror provided by the invention only needs one-time bonding, and the bonding is used for connecting the base and the upper layer structure, so that the requirement on alignment precision is low, the alignment precision of only 1-50 mu m needs to be met, and the method is easy to realize in the prior art.
(8) The invention realizes the manufacture of the internal oxide layer of the silicon chip by adopting the mode of oxygen ion implantation after etching, the manufactured oxide layer fluctuates along with the fluctuation of the surface structure of the silicon chip in the vertical direction, and the manufacture of the non-bonded vertical direction staggered structure is realized by the subsequent oxide layer release process, thereby completely eliminating the alignment error caused by the bonding process adopted by the traditional vertical staggered structure manufacture. The problems of uneven combination, fragments and the like which are easy to occur in bonding are avoided.
Drawings
FIG. 1 is an overall isometric view of a micromirror;
FIG. 2 is an overall left side view and a partial enlarged view of a micromirror;
FIG. 3 is a general top view of a micromirror;
FIG. 4 is an overall back side view of a micromirror;
FIG. 5 is an isometric view of the base;
FIG. 6 is an isometric view of a first insulation layer;
FIG. 7 is an isometric view of a first fixed layer;
FIG. 8 is an isometric view of a second insulation layer;
FIG. 9 is an isometric view of a layer of a mirror element;
FIG. 10 is an isometric view of a third insulation layer;
FIG. 11 is an isometric view of a second fixed layer;
FIG. 12 is an isometric view of a fourth insulation layer;
FIG. 13 is a comb drive capacitor formed by a fixed drive element and a rotating drive element;
FIG. 14 is a timing diagram of the driving voltages Vd1 and Vd 2;
fig. 15 shows a forward rotation state of the micromirror when the driving voltage Vd1 is Vd;
fig. 16 shows the negative rotation state of the micromirror when the driving voltage Vd2 is Vd;
FIG. 17 shows a comb detection capacitor formed by a fixed capacitor and a rotating capacitor;
FIG. 18 shows the state of the detection capacitor when the micromirror is rotated in the forward direction;
FIG. 19 is a diagram illustrating the detection of the capacitance state during the negative rotation of the micromirror;
FIG. 20(1) is a schematic view of silicon wafer preparation in example 3; FIG. 20(2) is a schematic diagram of the front surface first photolithography in embodiment 3; FIG. 20(3) is a schematic view of the first etching of the front surface in example 3; FIG. 20(4) is a schematic view of the first photolithography on the back surface in embodiment 3; FIG. 20(5) is a schematic view of the first etching of the back surface in example 3; FIG. 20(6) is a schematic diagram of front side oxygen ion implantation in example 3; FIG. 20(7) is a schematic diagram of backside oxygen ion implantation in example 3; FIG. 20(8) is a schematic view of front side polishing in example 3; FIG. 20(9) is a schematic view of back side polishing in example 3; FIG. 20(10) is a schematic diagram of the second photolithography on the front surface in embodiment 3; FIG. 20(11) is a schematic view of the second etching on the front surface in example 3; FIG. 20(12) is a schematic view of a second photolithography on the back surface in embodiment 3; FIG. 20(13) is a diagram illustrating a second etching on the backside in example 3; FIG. 20(14) is a schematic view of a susceptor prepared in embodiment 3; FIG. 20(15) is a schematic view of bonding in example 3; FIG. 20(16) is a schematic view showing the structure release of example 3; fig. 20(17) is a schematic view of the preparation of the front oxide layer in embodiment 3; FIG. 20(18) is a schematic diagram of the pad fabrication of embodiment 3;
FIG. 21 is a schematic view of a micromirror made in embodiment 4;
FIG. 22 is a schematic view of a micromirror made in embodiment 5;
in the figure, 1a substrate, 2 a first insulating layer, 3 a first fixed layer, 31 a first peripheral fixed structure, 301 a first fixed capacitor, 302 a second fixed capacitor, 303 a third fixed capacitor, 304 a fourth fixed capacitor, 311 a first fixed driving element, 312 a second fixed driving element, 4 a second insulating layer, 5 a reflecting element layer, 51 a mirror peripheral fixed structure, 530 a mirror body, 501 a first rotating capacitor, 502 a second rotating capacitor, 503 a third rotating capacitor, 504 a fourth rotating capacitor, 511 a first rotating driving element, 512 a second rotating driving element, 521 a first rotating shaft, 522 a second rotating shaft, 6 a third insulating layer, 7 a second fixed layer, 71a second peripheral fixed structure, fifth fixed capacitors, 706 a sixth fixed capacitor, 707 a seventh fixed capacitor, 705 an eighth fixed capacitor, 713 a third fixed driving element, 714 a fourth fixed driving element, 8 a fourth insulating layer, 9 bonding pads.
Detailed Description
The present invention will be further described with reference to the following examples.
The invention provides a micromirror with fully symmetric differential capacitor angle feedback, aiming at the problems that the existing micromirror without feedback has poor control precision, and the angle measurement scheme of the micromirror with angle feedback has the defects of complex system, low signal-to-noise ratio, incapability of being simultaneously suitable for high frequency and low frequency, poor process compatibility and the like. The micro-mirror provided by the invention integrates the angle detection sensor, the signal-to-noise ratio of the angle detection sensor is high, the rotation angle of the micro-mirror can be effectively detected in real time, and the control precision of the micro-mirror is improved; meanwhile, due to the adoption of the design of an integrated angle detection sensor, the micro-mirror chip comprises the angle sensor, and the micro-mirror has a compact structure, small volume and low power consumption; the micro-mirror chip is formed by one-time flow sheet through a micro-nano processing technology, the micro-mirror structure and function consistency and stability are high, and the subsequent packaging is simple; meanwhile, the micro-mirror processing technology and the material are conventional micro-nano processing technology and material, and the technology compatibility is high. The angle detection sensor adopts a symmetrical capacitive sensor design, so that the sensitivity is high, and the requirement on a subsequent processing circuit is low. By adopting the electrostatic driving and capacitance type detection sensor, the micro-mirror can be suitable for the requirements from low frequency to high frequency.
Example 1
This embodiment the micromirror that possesses complete symmetry formula differential capacitance angle feedback, see fig. 1-3, including base 1, base 1 upper surface is provided with first insulating layer 2, the upper surface of first insulating layer 2 is provided with first fixed layer 3, the upper surface of first fixed layer 3 is provided with second insulating layer 4, the upper surface of second insulating layer 4 is provided with reflective element layer 5, the upper surface of reflective element layer 5 is provided with third insulating layer 6, the upper surface of third insulating layer 6 is provided with second fixed layer 7, the upper surface of second fixed layer 7 is provided with fourth insulating layer 8, be provided with pad 9 on the fourth insulating layer 8. The number of the bonding pads is 13. The bonding pad is electrically communicated with each structural layer in a TSV (through hole communication) mode (the TSV technology is a general technology, and details are shown in Huzheng height, Su wei, Xugao Wei and Role, and applied to the research on the TSV technology of MOEMS integration [ J ] the technical report of sensing, 2019,32(05): 649-.
Further, the base 1 is a hollow frame-shaped structure surrounded by peripheral frames, as shown in fig. 4-5, the first insulating layer 2, the first fixing layer 3, the second insulating layer 4, the reflective element layer 5, the third insulating layer 6, the second fixing layer 7, and the fourth insulating layer 8 are sequentially and fixedly stacked on the hollow frame-shaped structure of the base 1.
Further, the first insulating layer 2, the second insulating layer 4, the reflective element layer 5, the third insulating layer 6 and the fourth insulating layer 8 are all planar structures; the first fixing layer 3 and the second fixing layer 7 have a stepped structure.
Further, as shown in fig. 6, the first insulating layer 2 is composed of a plurality of insulating thin layers disposed on the upper surface of the periphery of the hollow frame-shaped structure of the base 1; which functions to block the electrical connection between the base 1 and the first fixing layer 3. The insulating thin layer is made of high-resistance materials such as silicon oxide, silicon nitride and the like.
As shown in fig. 7, the first fixed layer 3 includes a first peripheral fixed structure 31, a first fixed capacitor 301, a second fixed capacitor 302, a third fixed capacitor 303, a fourth fixed capacitor 304, a first fixed driving element 311, and a second fixed driving element 312; a first fixed capacitor 301, a second fixed capacitor 302, a third fixed capacitor 303 and a fourth fixed capacitor 304 are arranged on the inner sides of the two axial ends of the first peripheral fixing structure 31; a first fixed driving element 311 and a second fixed driving element 312 are arranged on the inner sides of the two radial ends of the first peripheral fixing structure 31; the first fixed capacitor 301, the second fixed capacitor 302, the third fixed capacitor 303, the fourth fixed capacitor 304, the first fixed driving element 311 and the second fixed driving element 312 are all suspended comb tooth structures, and the roots of the comb tooth structures are all connected with the first peripheral fixed structure 31; the lower surface of the comb teeth part is flush with the lower surface of the first peripheral fixing structure 31, and the upper surface of the comb teeth part exceeds the upper surface of the first peripheral fixing structure 31 to form a stepped structure; the first peripheral securing structure 31 is connected to the first insulating layer 2.
Further, as shown in fig. 8, the second insulating layer 4 is composed of a plurality of insulating thin layers disposed on the upper surface of the first peripheral fixing structure 31; which functions to break the electrical connection between the first anchoring layer 3 and the mirror element layer 5. The insulating thin layer is made of high-resistance materials such as silicon oxide, silicon nitride and the like.
As shown in fig. 9, the reflective element layer 5 includes a mirror peripheral fixing structure 51, a mirror body 530, a first rotating capacitor 501, a second rotating capacitor 502, a third rotating capacitor 503, a fourth rotating capacitor 504, a first rotating driving element 511, and a second rotating driving element 512; the first rotating capacitor 501, the second rotating capacitor 502, the third rotating capacitor 503, the fourth rotating capacitor 504, the first rotating driving element 511 and the second rotating driving element 512 are all suspended comb tooth structures; the axial two side edges of the mirror body 530 are connected with the inner sides of the axial two side edges of the peripheral fixed structure 51 of the reflector through a first rotating shaft 521 and a second rotating shaft 522, the radial two side edges of the mirror body 530 are respectively connected with the comb tooth roots of a first rotating driving element 511 and a second rotating driving element 512, the two side edges of the first rotating shaft 521 are respectively connected with the comb tooth roots of a first rotating capacitor 501 and a second rotating capacitor 502, the two side edges of the second rotating shaft 522 are respectively connected with the comb tooth roots of a third rotating capacitor 503 and a fourth rotating capacitor 504, and the peripheral fixed structure 51 of the reflector is connected with the second insulating layer 4.
Further, as shown in fig. 10, the third insulating layer 6 is composed of a plurality of insulating thin layers provided on the upper surface of the mirror peripheral fixing structure 51; which functions to block the electrical connection between the mirror element layer 5 and the second anchoring layer 7. The insulating thin layer is made of high-resistance materials such as silicon oxide, silicon nitride and the like.
As shown in fig. 11, the second fixed layer 7 includes a second peripheral fixed structure 71, a fifth fixed capacitor 705, a sixth fixed capacitor 706, a seventh fixed capacitor 707, an eighth fixed capacitor 708, a third fixed driving element 713, and a fourth fixed driving element 714; a fifth fixed capacitor 705, a sixth fixed capacitor 706, a seventh fixed capacitor 707, and an eighth fixed capacitor 708 are provided on the inner sides of the two axial ends of the second peripheral fixed structure 71; the radial inner sides of the two ends of the second peripheral fixing structure 71 are provided with a third fixed driving element 713 and a fourth fixed driving element 714; the fifth fixed capacitor 705, the sixth fixed capacitor 706, the seventh fixed capacitor 707, the eighth fixed capacitor 708, the third fixed driving element 713 and the fourth fixed driving element 714 are all suspended comb tooth structures, and the roots of the comb tooth structures are all connected with the second peripheral fixed structure 71; the upper surface of the comb teeth part is flush with the upper surface of the second peripheral fixing structure 71, and the lower surface of the comb teeth part exceeds the lower surface of the second peripheral fixing structure 71 to form a stepped structure; the second peripheral securing structure 71 is connected to the third insulating layer 6;
as shown in fig. 12, the fourth insulating layer 8 is formed by a plurality of insulating thin layers disposed on the upper surface of the second peripheral fixing structure 71; which functions to provide the required electrical isolation for the wire bonding of the micromirror chip to peripheral circuits. The insulating thin layer is made of high-resistance materials such as silicon oxide, silicon nitride and the like.
Further, as shown in fig. 13, the first fixed driving element 311, the first rotational driving element 511, and the third fixed driving element 713 constitute a set of differential comb-drive capacitances; the second fixed drive element 312, the second rotational drive element 512, and the fourth fixed drive element 714 form a set of differential comb drive capacitors;
the first and fourth fixed driving elements 311 and 714 apply a driving voltage Vd1, the second and third fixed driving elements 312 and 713 apply a driving voltage Vd2, and the first and second rotational driving elements 511 and 512 are grounded. The Vd1 and Vd2 are square wave signals with opposite phase, the minimum value of the two is 0, the amplitude is Vd, and the timing of the driving voltages Vd1 and Vd2 is shown in fig. 14.
When Vd1 is Vd, the mirror element rotation direction is defined as the forward direction, as shown in fig. 15; when Vd2 is Vd, the mirror element rotation direction is defined as negative, as shown in fig. 16.
As shown in fig. 17, the first fixed capacitor 301 and the first rotating capacitor 501 form a set of comb-teeth detection capacitors, and the fifth fixed capacitor 705 and the first rotating capacitor 501 form a set of comb-teeth detection capacitors; the second fixed capacitor 302 and the second rotating capacitor 502 form a group of comb detection capacitors, and the sixth fixed capacitor 706 and the second rotating capacitor 502 form a group of comb detection capacitors; the third fixed capacitor 303 and the third rotating capacitor 503 form a group of comb detection capacitors, and the seventh fixed capacitor 707 and the third rotating capacitor 503 form a group of comb detection capacitors; the fourth fixed capacitor 304 and the fourth rotating capacitor 504 form a group of comb detection capacitors, and the eighth fixed capacitor 708 and the fourth rotating capacitor 504 form a group of comb detection capacitors; the comb tooth driving capacitor sets are arranged in a symmetrical structure; the comb detection capacitor bank is arranged in a symmetrical structure.
The first rotating capacitor 501, the second rotating capacitor 502, the third rotating capacitor 503 and the fourth rotating capacitor 504 are all grounded. The reflector element generates rotary vibration around the rotating shaft under the action of electrostatic force, and the output of the corresponding comb tooth detection capacitor set changes.
When the micromirror rotates forward as shown in fig. 18, the output values δ C1, δ C3, δ C6, and δ C8 of the first fixed capacitor 301, the third fixed capacitor 303, the sixth fixed capacitor 706, and the eighth fixed capacitor 708 at this time increase; the output values δ C2, δ C4, δ C5, and δ C7 of the second fixed capacitance 302, the fourth fixed capacitance 304, the fifth fixed capacitance 705, and the seventh fixed capacitance 707 decrease. Due to structural symmetry, δ C1- δ C3- δ C6- δ C8- δ C2- δ C4- δ C5- δ C7- δ C, and the total detected capacitance variation Δ C (δ C1+ δ C3+ δ C6+ δ C8) - (- δ C2- δ C4- δ C5- δ C7) -8 δ C (θ) are output in a differential mode.
When the micromirror is rotated in the negative direction as shown in FIG. 19, the output values δ C1, δ C3, δ C6 and δ C8 of the first fixed capacitor 301, the third fixed capacitor 303, the sixth fixed capacitor 706 and the eighth fixed capacitor 708 are decreased at this time; the output values δ C2, δ C4, δ C5, and δ C7 of the second fixed capacitance 302, the fourth fixed capacitance 304, the fifth fixed capacitance 705, and the seventh fixed capacitance 707 increase. Due to structural symmetry, - δ C1 ═ δ C3 ═ δ C6 ═ δ C8 ═ δ C2 ═ δ C4 ═ δ C5 ═ δ C7 ═ δ C, the total detected capacitance variation Δ C is (δ C2+ δ C4+ δ C5+ δ C7) - (- δ C1- δ C3- δ C6- δ C8) ═ 8 δ C ═ f (θ) in the same differential output manner.
The total detection capacitance variation delta C is a function of the rotation angle theta of the reflector element, the delta C is used as real-time angle feedback to be introduced into driving signals Vd1 and Vd2, and the driving signals are adjusted according to the real-time angle feedback, so that the driving control precision can be effectively improved.
Further, the base 1 and the first insulating layer 2, the first insulating layer 2 and the first fixed layer 3, the first fixed layer 3 and the second insulating layer 4, the second insulating layer 4 and the reflective element layer 5, the reflective element layer 5 and the third insulating layer 6, the third insulating layer 6 and the second fixed layer 7, and the second fixed layer 7 and the fourth insulating layer 8 are connected in a bonding manner; the base 1 may be a hollow frame structure of a circle, an ellipse, a diamond, a rectangle or a square.
Example 2
This embodiment the micromirror that possesses complete symmetry formula differential capacitance angle feedback, including base 1, 1 upper surface of base is provided with first insulating layer 2, the upper surface of first insulating layer 2 is provided with first fixed layer 3, the upper surface of first fixed layer 3 is provided with second insulating layer 4, the upper surface of second insulating layer 4 is provided with reflective element layer 5, reflective element layer 5's upper surface is provided with third insulating layer 6, the upper surface of third insulating layer 6 is provided with second fixed layer 7, the upper surface of second fixed layer 7 is provided with fourth insulating layer 8, be provided with pad 9 on the fourth insulating layer 8. The base 1 is a hollow frame-shaped structure surrounded by peripheral frames, as shown in fig. 4-5, the first insulating layer 2, the first fixing layer 3, the second insulating layer 4, the reflecting element layer 5, the third insulating layer 6, the second fixing layer 7 and the fourth insulating layer 8 are sequentially and fixedly stacked on the hollow frame-shaped structure of the base 1.
Example 3 concrete production method
To better explain the method for manufacturing the micromirror with fully symmetric differential capacitance angle feedback in embodiment 1, the manufacturing method will be described with reference to fig. 20(1) -20 (18).
The manufacturing method of the micromirror with the angle feedback of the symmetrical differential capacitor comprises the following steps:
(1) a silicon wafer is prepared. The silicon chip is monocrystalline silicon or polycrystalline silicon, is polished on double surfaces, has the thickness of 150 mu m and the resistivity of 0.01 omega cm. See FIG. 20 (1).
(2) And performing primary photoetching on the front surface, and defining a corresponding pattern with the position changed in the vertical direction of the front surface oxygen ion implantation area. See fig. 20 (2).
(3) And (3) carrying out dry etching on the front surface for the first time, and etching a groove-shaped structure on the front surface of the silicon wafer for subsequent oxygen ion implantation to realize the position change of the oxygen ion implantation in the vertical direction. And removing the photoresist on the front side of the silicon wafer after the dry etching is finished. The depth of the etched groove-like structure was 25 μm. See fig. 20 (3).
(4) And carrying out back surface first photoetching, namely reversing the silicon wafer, carrying out photoetching on the back surface, wherein the used mask plate graph is a mirror image of the mask plate graph used for the front surface first photoetching, and defining a corresponding graph with the position changed in the vertical direction of the back surface oxygen ion implantation area. See fig. 20 (4).
(5) And (3) carrying out dry etching on the back for the first time, and etching a groove-shaped structure on the back of the silicon wafer for subsequent oxygen ion implantation to realize the position change of the oxygen ion implantation in the vertical direction. And removing the photoresist on the back of the silicon wafer after the dry etching is finished. The depth of the etched groove-like structure was 25 μm. See fig. 20 (5).
(6) Performing oxygen ion implantation on the front surface of the silicon wafer, and selecting proper implantation energy according to the required oxygen ion depth; and forming an oxide layer at a position with a certain distance from the front surface of the silicon wafer after oxygen ion implantation. The distance between the oxide layer and the front surface of the silicon wafer is different when the injection energy is different, the lower the energy is, the smaller the distance is, the larger the energy is, and the larger the distance is; because the dry etching is carried out in the step 3, the groove-shaped structure is formed on the front surface of the silicon wafer before the oxygen ion implantation, that is, the front surface of the silicon wafer is not a plane but has the height fluctuation, in the same oxygen ion implantation, although the implantation energy is constant and the distance between the oxide layer and the front surface of the silicon wafer is the same, the oxide layer formed by the implantation is not a plane but has the fluctuation in the vertical direction corresponding to the fluctuation of the front surface of the silicon wafer because the front surface of the silicon wafer has the height fluctuation. The oxygen ion implantation depth was 50 μm. See fig. 20 (6).
(7) Back oxygen ion implantation, wherein the back of the silicon wafer is subjected to integral oxygen ion implantation, and proper implantation energy is selected according to the required oxygen ion depth; and forming an oxide layer at a position away from the surface of the back side of the silicon wafer by a certain distance after oxygen ion implantation. The distance between the oxide layer and the back surface of the silicon wafer is different when the injection energy is different, the lower the energy is, the smaller the distance is, the larger the energy is, and the larger the distance is; since the dry etching is performed in step 3, a groove-like structure is formed on the surface of the back surface of the silicon wafer before the oxygen ion implantation, that is, the surface of the back surface of the silicon wafer is not a plane but has undulations, in the same oxygen ion implantation, although the implantation energy is constant and the distance between the oxide layer and the surface of the back surface of the silicon wafer is the same, the oxide layer formed by the implantation is not a plane but has undulations in the vertical direction corresponding to the undulations of the surface of the back surface of the silicon wafer due to the undulations of the surface of the back surface of the silicon wafer. The depth of oxygen ion implantation at this time was 50 μm, which was the same as the depth of oxygen ion implantation in step 6. See fig. 20 (7).
(8) And thinning and polishing the front surface, removing the groove-shaped structure used for assisting oxygen ion implantation on the front surface, and recovering the polished surface of the front surface. See fig. 20 (8).
(9) And (4) back thinning and polishing, namely removing the groove-shaped structure used for assisting oxygen ion implantation on the back surface, and recovering the polished surface of the back surface. After the process of the step is finished, the silicon wafer forms a five-layer structure which comprises a first fixed layer, a second insulating layer, a reflector element layer, a third insulating layer and a second fixed layer from bottom to top; wherein the reflector element layer is of a planar structure and has a thickness of 50 μm, and the first and second fixed layers are of a stepped structure and have a thickness of 50 μm; the first and second pinned layers are symmetric about a mirror element layer center plane. The second and third insulating layers are equal in thickness, both 1 μm, and are symmetrical about the central plane of the mirror element layer. See fig. 20 (9).
(10) And performing second photoetching on the front surface, and defining graphs corresponding to a third fixed driving element, a fourth fixed driving element, a fifth fixed capacitor, a sixth fixed capacitor, a seventh fixed capacitor and an eighth fixed capacitor of the second fixed layer. See fig. 20 (10).
(11) And performing second dry etching on the front surface to etch a third fixed driving element, a fourth fixed driving element, a fifth fixed capacitor, a sixth fixed capacitor, a seventh fixed capacitor and an eighth fixed capacitor structure. And removing the photoresist on the front side of the silicon wafer after etching. This etching depth is equal to the depth of the oxygen ion implantation in step 6, and is 50 μm. See fig. 20 (11).
(12) And performing secondary photoetching on the back surface, namely reversing the silicon wafer, performing photoetching on the back surface of the silicon wafer, and defining graphs corresponding to the first fixed driving element, the second fixed driving element, the first fixed capacitor, the second fixed capacitor, the third fixed capacitor and the fourth fixed capacitor. See fig. 20 (12).
(13) And carrying out dry etching on the back surface for the second time to etch a first fixed driving element, a second fixed driving element, a first fixed capacitor, a second fixed capacitor, a third fixed capacitor and a fourth fixed capacitor structure. And removing the photoresist on the back of the silicon wafer after etching. This etching depth is equal to the oxygen ion implantation depth in step 7, and is 50 μm. See fig. 20 (13).
(14) The preparation method comprises the steps of preparing a base, wherein monocrystalline silicon wafers or polycrystalline silicon wafers are adopted, the resistivity is 1000 omega cm, and the thickness is 400 mu m. Firstly, depositing or thermally oxidizing the surface of a monocrystalline silicon wafer or a polycrystalline silicon wafer used for preparing a base to form an oxide layer as a first insulating layer, wherein the thickness of the oxide layer is 1 mu m. And manufacturing the base with the frame-shaped structure by adopting a dry etching method. See fig. 20 (14).
(15) And bonding the base with the silicon wafer finished in the step 13 (back surface second dry etching). When bonding, the upper surface of the base is contacted with the lower surface of the silicon wafer finished in the step 13, and the hollow area of the frame-shaped structure of the base is larger than the areas of the silicon wafer finished in the step 13 corresponding to the first fixed driving element, the second fixed driving element, the first fixed capacitor, the second fixed capacitor, the third fixed capacitor and the fourth fixed capacitor, so that the bonding alignment requirement is low, and only the alignment tolerance of plus or minus 50 micrometers needs to be ensured, as shown in fig. 20 (15).
(16) And (3) releasing the structure, namely putting the bonded silicon wafer into a hydrofluoric acid wet etching groove or hydrogen fluoride dry releasing equipment, and etching to remove the two oxide layers formed in the step 6 and the step 7, so that the release of the structures contained in the first fixed layer, the reflector element layer and the second fixed layer is realized. See fig. 20 (16).
(17) And preparing a front-side oxide layer, and depositing a silicon oxide layer on the upper surface of the silicon wafer after the release of the step 16 (structure release) is completed, or preparing an oxide layer as a fourth insulating layer by a thermal oxidation method. The thickness of the fourth insulating layer is 1 μm. See fig. 20 (17).
(18) And (4) manufacturing the bonding pad, namely manufacturing the bonding pad by adopting a sputtering or evaporation mode after the structure is manufactured, wherein the used mask is a hard mask. See fig. 20 (18).
The above is a preferred embodiment of the method for manufacturing a micromirror with angle feedback of a symmetric differential capacitor, wherein some steps can be adjusted according to specific structures and process conditions, for example, front-side lithography and etching can be sequentially replaced with back-side lithography and etching, the sequence of front-side oxygen ion implantation and back-side oxygen ion implantation can be replaced, and structure release and bonding can be sequentially replaced according to requirements.
In the embodiment, the five-layer structure is realized on the initial monocrystalline silicon wafer or polycrystalline silicon wafer through oxygen ion implantation, and a three-layer, seven-layer or even more-layer structure can be realized by adopting an oxygen ion implantation mode according to the requirement.
It is within the scope of the claimed method to simply change some of the process sequences of the method, or to change the number of layers implemented.
EXAMPLE 4 method of manufacturing micromirror
As shown in FIG. 21, the difference from example 3 is that the thickness of the base is 400 μm, the thicknesses of the first pinned layer and the second pinned layer are 25 μm, the thickness of the mirror element layer is 100 μm, and the depth of the oxygen ion implantation is 25 μm. The depth of the groove-shaped structure formed by the primary dry etching of the front side and the back side is 10 nm. The thickness of each oxide layer was 0.2. mu.m. The resistivity of the base is 1 Ω cm. First, second and mirror element layer resistivities 10-4Omega cm. (the dimensions are not to scale in the figures)
EXAMPLE 5 method of manufacturing micromirror
As shown in fig. 22, the difference from embodiment 3 is that the susceptor has a thickness of 100 μm. The thickness of the first fixed layer and the second fixed layer is 60 mu m, the thickness of the reflector element layer is 60 mu m, and the implantation depth of oxygen ions is 60 mu m. The depth of the groove-shaped structure formed by the first dry etching on the front side and the back side is 1 mu m. The thickness of each oxide layer was 5 μm. Resistivity of the substrate 104Omega cm. First, second and mirror element layer resistivities 10-4Ω·㎝。
The specific structures, parameters and manufacturing methods shown in fig. 21 and 22 are preferred embodiments, and are not limited to the parameters of the disclosure, and it is within the scope of the present invention to simply change the shapes, numbers, process parameters or process sequences of the structures.
The base 1, the first fixed layer 3 and the second fixed layer 7 are made of any one of monocrystalline silicon, polycrystalline silicon and amorphous silicon; the material of the reflecting element layer 5 is selected from any one of monocrystalline silicon, polycrystalline silicon, amorphous silicon or high molecular polymer; the resistivities of the first fixed layer 3, the reflecting element layer 5 and the second fixed layer 7 are all less than 1 omega cm; the first insulating layer 2, the second insulating layer 4, the third insulating layer 6 and the fourth insulating layer 8 are made of any one material selected from silicon oxide, silicon nitride, silicon carbide or high molecular polymer; the resistivities of the first insulating layer 2, the second insulating layer 4, the third insulating layer 6 and the fourth insulating layer 8 are all larger than 10 omega cm. The high molecular polymer is any one selected from polydimethylsiloxane, SU8 glue, epoxy resin, polyamide, polyimide, polypropylene, polyethylene, polyvinyl chloride, polystyrene, polyethylene terephthalate and polymethyl methacrylate.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and is not intended to limit the invention to the particular forms disclosed. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.

Claims (12)

1. A micromirror with fully symmetric differential capacitive angle feedback, comprising: including base (1), base (1) upper surface is provided with first insulating layer (2), the upper surface of first insulating layer (2) is provided with first fixed layer (3), the upper surface of first fixed layer (3) is provided with second insulating layer (4), the upper surface of second insulating layer (4) is provided with reflective element layer (5), the upper surface of reflective element layer (5) is provided with third insulating layer (6), the upper surface of third insulating layer (6) is provided with second fixed layer (7), the upper surface of second fixed layer (7) is provided with fourth insulating layer (8), be provided with pad (9) on fourth insulating layer (8).
2. The micromirror with fully symmetric differential capacitive angle feedback according to claim 1, wherein: the base (1) is a hollow frame-shaped structure surrounded by peripheral frames, and the first insulating layer (2), the first fixing layer (3), the second insulating layer (4), the reflecting element layer (5), the third insulating layer (6), the second fixing layer (7) and the fourth insulating layer (8) are overlapped and fixed on the hollow frame-shaped structure of the base (1) in sequence.
3. The micromirror with fully symmetric differential capacitive angle feedback according to claim 1, wherein: the first insulating layer (2), the second insulating layer (4), the reflecting element layer (5), the third insulating layer (6) and the fourth insulating layer (8) are all of a planar structure; the first fixed layer (3) and the second fixed layer (7) are of a stepped structure.
4. The micromirror of claim 3 with fully symmetric differential capacitive angle feedback, wherein: the first insulating layer (2) is composed of a plurality of insulating thin layers arranged on the upper surface of the periphery of the hollow frame-shaped structure of the base (1); the first fixed layer (3) comprises a first peripheral fixed structure (31), a first fixed capacitor (301), a second fixed capacitor (302), a third fixed capacitor (303), a fourth fixed capacitor (304), a first fixed driving element (311) and a second fixed driving element (312); a first fixed capacitor (301), a second fixed capacitor (302), a third fixed capacitor (303) and a fourth fixed capacitor (304) are arranged on the inner sides of the two axial ends of the first peripheral fixed structure (31); a first fixed driving element (311) and a second fixed driving element (312) are arranged on the inner sides of the two radial ends of the first peripheral fixing structure (31); the first fixed capacitor (301), the second fixed capacitor (302), the third fixed capacitor (303), the fourth fixed capacitor (304), the first fixed driving element (311) and the second fixed driving element (312) are all suspended comb tooth structures, and the roots of the comb tooth structures are all connected with the first peripheral fixed structure (31); the lower surface of the comb teeth part is flush with the lower surface of the first peripheral fixing structure (31), and the upper surface of the comb teeth part exceeds the upper surface of the first peripheral fixing structure (31) to form a stepped structure; the first peripheral fixing structure (31) is connected with the first insulating layer (2).
5. The micromirror of claim 4 with fully symmetric differential capacitive angle feedback, wherein: the second insulating layer (4) is composed of a plurality of insulating thin layers arranged on the upper surface of the first peripheral fixing structure (31); the reflecting element layer (5) comprises a reflecting mirror peripheral fixing structure (51), a mirror body (530), a first rotating capacitor (501), a second rotating capacitor (502), a third rotating capacitor (503), a fourth rotating capacitor (504), a first rotating driving element (511) and a second rotating driving element (512); the first rotating capacitor (501), the second rotating capacitor (502), the third rotating capacitor (503), the fourth rotating capacitor (504), the first rotating driving element (511) and the second rotating driving element (512) are all suspended comb tooth structures; the utility model discloses a mirror, including the mirror body (530), the mirror body, the radial both sides limit of mirror body (530) is connected with the broach root that first rotation drive component (511), second rotation drive component (512) respectively, the radial both sides limit of mirror body (530) is connected with the broach root of first rotation drive component (511), second rotation drive component (512) respectively, first pivot (521) both sides limit is connected with the broach root of first rotation capacitance (501), second rotation capacitance (502) respectively, second pivot (522) both sides limit is connected with the broach root of third rotation capacitance (503), fourth rotation capacitance (504) respectively, mirror peripheral fixed knot constructs (51) and is connected with second insulating layer (4).
6. The micromirror of claim 5 with fully symmetric differential capacitive angle feedback, wherein: the third insulating layer (6) is composed of a plurality of insulating thin layers arranged on the upper surface of the reflector periphery fixing structure (51); the second fixed layer (7) comprises a second peripheral fixed structure (71), a fifth fixed capacitor (705), a sixth fixed capacitor (706), a seventh fixed capacitor (707), an eighth fixed capacitor (708), a third fixed driving element (713) and a fourth fixed driving element (714); a fifth fixed capacitor (705), a sixth fixed capacitor (706), a seventh fixed capacitor (707), and an eighth fixed capacitor (708) are arranged on the inner sides of the two axial ends of the second peripheral fixed structure (71); a third fixed driving element (713) and a fourth fixed driving element (714) are arranged on the inner sides of the two radial ends of the second peripheral fixed structure (71); the fifth fixed capacitor (705), the sixth fixed capacitor (706), the seventh fixed capacitor (707), the eighth fixed capacitor (708), the third fixed driving element (713) and the fourth fixed driving element (714) are all suspended comb tooth structures, and the roots of the comb tooth structures are all connected with a second peripheral fixed structure (71); the upper surface of the comb teeth part is flush with the upper surface of the second peripheral fixing structure (71), and the lower surface of the comb teeth part exceeds the lower surface of the second peripheral fixing structure (71) to form a stepped structure; the second peripheral fixing structure (71) is connected with the third insulating layer (6); the fourth insulating layer (8) is composed of a plurality of insulating thin layers arranged on the upper surface of the second peripheral fixing structure (71).
7. The micromirror of claim 6 with fully symmetric differential capacitive angle feedback, wherein: the first fixed driving element (311), the first rotating driving element (511) and the third fixed driving element (713) form a group of comb-tooth driving capacitors; the second fixed driving element (312), the second rotary driving element (512) and the fourth fixed driving element (714) form a group of comb tooth driving capacitors; the first fixed capacitor (301) and the first rotating capacitor (501) form a group of comb tooth detection capacitors, and the fifth fixed capacitor (705) and the first rotating capacitor (501) form a group of comb tooth detection capacitors; the second fixed capacitor (302) and the second rotating capacitor (502) form a group of comb detection capacitors, and the sixth fixed capacitor (706) and the second rotating capacitor (502) form a group of comb detection capacitors; the third fixed capacitor (303) and the third rotating capacitor (503) form a group of comb detection capacitors, and the seventh fixed capacitor (707) and the third rotating capacitor (503) form a group of comb detection capacitors; the fourth fixed capacitor (304) and the fourth rotating capacitor (504) form a group of comb detection capacitors, and the eighth fixed capacitor (708) and the fourth rotating capacitor (504) form a group of comb detection capacitors; the comb tooth driving capacitor sets are arranged in a symmetrical structure; the comb detection capacitor bank is arranged in a symmetrical structure.
8. The micromirror with fully symmetric differential capacitive angle feedback according to any of claims 2 to 6, wherein: the base (1) is connected with the first insulating layer (2), the first insulating layer (2) is connected with the first fixing layer (3), the first fixing layer (3) is connected with the second insulating layer (4), the second insulating layer (4) is connected with the reflecting element layer (5), the reflecting element layer (5) is connected with the third insulating layer (6), the third insulating layer (6) is connected with the second fixing layer (7), and the second fixing layer (7) is connected with the fourth insulating layer (8) in a bonding mode; the base (1) can be a hollow frame-shaped structure with a circular shape, an oval shape, a diamond shape, a rectangular shape or a square shape.
9. The micromirror with fully symmetric differential capacitive angle feedback according to claim 1, wherein: the base (1), the first fixing layer (3) and the second fixing layer (7) are made of any one of monocrystalline silicon, polycrystalline silicon and amorphous silicon; the material of the reflecting element layer (5) is selected from any one of monocrystalline silicon, polycrystalline silicon, amorphous silicon or high molecular polymer; the resistivity of the first fixed layer (3), the resistivity of the reflecting element layer (5) and the resistivity of the second fixed layer (7) are all less than 1 omega cm; the first insulating layer (2), the second insulating layer (4), the third insulating layer (6) and the fourth insulating layer (8) are made of any one of silicon oxide, silicon nitride, silicon carbide and high polymer; the resistivities of the first insulating layer (2), the second insulating layer (4), the third insulating layer (6) and the fourth insulating layer (8) are all larger than 10 omega cm.
10. The micromirror of claim 9 with fully symmetric differential capacitive angle feedback, wherein: the high molecular polymer is any one selected from polydimethylsiloxane, SU8 glue, epoxy resin, polyamide, polyimide, polypropylene, polyethylene, polyvinyl chloride, polystyrene, polyethylene terephthalate and polymethyl methacrylate.
11. The method for fabricating a micromirror with fully symmetric differential capacitive angle feedback according to any of claims 1 to 7, comprising the steps of: (1) preparing a silicon wafer; (2) carrying out front-side first photoetching; (3) carrying out first dry etching on the front surface; (4) carrying out back surface first photoetching; (5) carrying out first dry etching on the back; (6) front oxygen ion implantation; (7) back oxygen ion implantation; (8) thinning and polishing the front side; (9) thinning and polishing the back; (10) carrying out second photoetching on the front surface; (11) carrying out second dry etching on the front surface; (12) carrying out secondary photoetching on the back surface; (13) carrying out secondary dry etching on the back; (14) preparing a base; (15) bonding the base with the silicon wafer subjected to the second dry etching on the back surface in the step 13; (16) releasing the structure; (17) preparing a front oxide layer; (18) and manufacturing a bonding pad.
12. The method of claim 11, comprising the steps of:
(1) preparing a silicon wafer, wherein the silicon wafer is monocrystalline silicon or polycrystalline silicon, the double surfaces of the silicon wafer are polished, the thickness of the silicon wafer is 50-300 mu m, and the resistivity of the silicon wafer is less than 0.01 omega cm;
(2) performing front-surface first photoetching to define a corresponding graph with the position of the front-surface oxygen ion implantation area changed in the vertical direction;
(3) the front side is etched by a dry method for the first time, and a groove-shaped structure is etched on the front side of the silicon wafer and used for subsequent oxygen ion implantation to realize the position change of the oxygen ion implantation in the vertical direction; removing the photoresist on the front side of the silicon wafer after the dry etching is finished; the depth of the groove-shaped structure realized in the step is 10nm-10 mu m;
(4) carrying out back first photoetching, namely reversing the silicon wafer, carrying out photoetching on the back, wherein the mask plate graph is a mirror image of the mask plate graph used for the front first photoetching, and defining a corresponding graph with the back oxygen ion implantation area changed in the vertical direction;
(5) the first dry etching is carried out on the back, and a groove-shaped structure is etched on the back of the silicon wafer and used for subsequent oxygen ion implantation to realize the position change of the oxygen ion implantation in the vertical direction; removing the photoresist on the back surface of the silicon wafer after the dry etching is finished, wherein the back groove-shaped structure realized in the step is symmetrical with the front groove-shaped structure realized in the step (3) about the neutral layer of the silicon wafer; the depth of the back groove-shaped structure realized in the step is 10nm-10 mu m;
(6) performing oxygen ion implantation on the front surface of the silicon wafer, and selecting proper implantation energy according to the required oxygen ion depth; forming an oxide layer at a position with a certain distance from the surface of the front side of the silicon wafer after oxygen ion implantation; the distance between the oxide layer and the front surface of the silicon wafer is different when the injection energy is different, the lower the energy is, the smaller the distance is, the larger the energy is, and the larger the distance is; because the dry etching is carried out in the step (3), a groove-shaped structure is formed on the front surface of the silicon wafer before oxygen ion implantation, namely the front surface of the silicon wafer is not a plane but has high and low undulations, in the same oxygen ion implantation, although the implantation energy is constant, the distance between the oxide layer and the front surface of the silicon wafer is the same, the oxide layer formed by implantation is not a plane but has the undulations in the vertical direction corresponding to the undulations of the front surface of the silicon wafer because the front surface of the silicon wafer has the high and low undulations; the implantation depth of the oxygen ions on the front surface is 5-100 μm;
(7) back oxygen ion implantation, wherein the back of the silicon wafer is subjected to integral oxygen ion implantation, and proper implantation energy is selected according to the required oxygen ion depth; forming an oxide layer at a position away from the surface of the back of the silicon wafer by a certain distance after oxygen ion implantation; the distance between the oxide layer and the back surface of the silicon wafer is different when the injection energy is different, the lower the energy is, the smaller the distance is, the larger the energy is, and the larger the distance is; because the dry etching is carried out in the step (3), a groove-shaped structure is formed on the surface of the back surface of the silicon wafer before the oxygen ion implantation, namely the surface of the back surface of the silicon wafer is not a plane but has the height fluctuation, in the same oxygen ion implantation, although the implantation energy is constant, the distance between the oxide layer and the surface of the back surface of the silicon wafer is the same, the oxide layer formed by the implantation is not a plane but has the fluctuation in the vertical direction corresponding to the fluctuation of the surface of the back surface of the silicon wafer because the surface of the back surface of the silicon wafer has the height fluctuation. The implantation depth of the back oxygen ions is equal to that of the front oxygen ions in the step (6);
(8) thinning and polishing the front surface, removing the groove-shaped structure used for assisting oxygen ion implantation on the front surface, and recovering the polished surface of the front surface;
(9) back thinning and polishing, namely removing the groove-shaped structure used for assisting oxygen ion implantation on the back surface and recovering the polished surface of the back surface; after the process of the step is finished, the silicon wafer forms a five-layer structure which comprises a first fixed layer, a second insulating layer, a reflector element layer, a third insulating layer and a second fixed layer from bottom to top; wherein the reflector element layer is of a planar structure and has a thickness of 5-100 μm, and the first and second fixed layers are of a stepped structure and have a thickness of 5-100 μm; the first and second pinned layers are symmetric about a mirror element layer center plane; the thicknesses of the second insulating layer and the third insulating layer are equal and are both 0.2-5 mu m, and the two insulating layers are symmetrical about the central plane of the reflector element layer;
(10) performing second photoetching on the front surface, and defining graphs corresponding to a third fixed driving element, a fourth fixed driving element, a fifth fixed capacitor, a sixth fixed capacitor, a seventh fixed capacitor and an eighth fixed capacitor of a second fixed layer;
(11) performing second dry etching on the front surface to etch a third fixed driving element, a fourth fixed driving element, a fifth fixed capacitor, a sixth fixed capacitor, a seventh fixed capacitor and an eighth fixed capacitor structure; removing the photoresist on the front side of the silicon wafer after etching; the etching depth is equal to the implantation depth of the front oxygen ions in the step (6);
(12) performing back-side second photoetching, namely reversing the silicon wafer, performing photoetching on the back side of the silicon wafer, and defining graphs corresponding to a first fixed driving element, a second fixed driving element, a first fixed capacitor, a second fixed capacitor, a third fixed capacitor and a fourth fixed capacitor;
(13) performing dry etching on the back surface for the second time to etch a first fixed driving element, a second fixed driving element, a first fixed capacitor, a second fixed capacitor, a third fixed capacitor and a fourth fixed capacitor structure; removing the photoresist on the back of the silicon wafer after etching; the etching depth is equal to the back oxygen ion implantation depth in the step 7;
(14) preparing a base by using monocrystalline silicon wafers or polycrystalline silicon wafers, wherein the resistivity is greater than 0.1 omega cm and the thickness is 100-800 mu m; firstly, depositing or thermally oxidizing the surface of a monocrystalline silicon wafer or a polycrystalline silicon wafer used for preparing a base to form an oxide layer serving as a first insulating layer, wherein the thickness of the oxide layer is 0.2-5 microns; manufacturing a base with a frame-shaped structure by adopting a dry etching or wet etching method;
(15) bonding the base with the silicon wafer finished in the step 13 (back surface second dry etching); the upper surface of the base is contacted with the lower surface of the silicon wafer finished in the step 13 during bonding, and the hollow area of the frame-shaped structure of the base is larger than the areas of the silicon wafer finished in the step 13 corresponding to the first fixed driving element, the second fixed driving element, the first fixed capacitor, the second fixed capacitor, the third fixed capacitor and the fourth fixed capacitor, so that the bonding alignment requirement is low, only the alignment tolerance of plus and minus 1-50 μm is required to be ensured, and the specific tolerance is determined according to the size of a specific device;
(16) releasing the structure, namely putting the bonded silicon wafer into a hydrofluoric acid wet etching groove or hydrogen fluoride dry releasing equipment, and etching to remove the two oxide layers formed in the step (6) and the step (7), so that the release of the structures contained in the first fixed layer, the reflector element layer and the second fixed layer is realized;
(17) preparing a front oxide layer, namely depositing a silicon oxide layer on the upper surface of the silicon chip after the structure in the step (16) is released, or preparing the oxide layer by a thermal oxidation method to be used as a fourth insulating layer; the thickness of the fourth insulating layer is 0.2-5 μm;
(18) and (4) manufacturing the bonding pad, namely manufacturing the bonding pad by adopting a sputtering or evaporation mode after the structure is manufactured, wherein the used mask is a hard mask.
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