CN114371551B - A kind of micromirror structure and preparation method thereof - Google Patents

Abstract

The invention relates to the technical field of micro-nano processing, in particular to a micromirror structure and a preparation method thereof. The substrate wafer includes an opposite first surface and a second surface, and the driving electrode layer is arranged on the first surface; the substrate wafer and the driving electrode layer are provided with through holes; the first An insulating layer is disposed on the surface of the driving electrode layer and the inner wall of the through hole; the first end of the support beam is connected to the fixed layer through the through hole, and the support beam is connected to the through hole There is a first preset gap between them; the fixed layer is arranged on the second surface; the first driving electrode, the second driving electrode and the shielding electrode are arranged in the driving electrode layer; the micromirror is arranged on the On the second end of the support beam, there is a second preset gap between the micromirror and the first insulating layer. The micromirror structure described in the embodiments of the present application can reduce the unit size while ensuring that the in-plane lateral displacement of the micromirror is comparable to the wavelength of the incident light.

Description

A kind of micromirror structure and preparation method thereof

technical field

The invention relates to the technical field of micro-nano processing, in particular to a micromirror structure and a preparation method thereof.

Background technique

The integrated micromirror realizes the modulation of the laser beam through the movement of the micromirror, so that the laser beam can realize spatial scanning, and is the core device of systems such as lidar.

The integrated micromirror refers to a movable micromirror fabricated on a wafer such as a silicon wafer using Micro Electro-Mechanical System technology (Micro Electro-Mechanical System, MEMS). Its movement mode can be roughly divided into two categories. One is that the micromirror moves away from its own plane, such as the digital mirror device (Digital Mirror Device, DMD) of Texas Instruments, where the mirror surface deflects around a support axis parallel to the surface of the wafer. Another type of micromirror is to move parallel to the surface of the wafer in its own plane, such as the MEMS optical phased array (Youmin Wang, Guangya Zhou, Xiaosheng Zhang, Kyungmok Kwon published by Wang Youmin of the University of California, Berkeley et al. ,Pierre-A.Blanche,Nicholas Triesualt,Kyoung-Sik Yu,and Ming C.Wu,2D broadband beamsteering with large-scale MEMS optical phased array,Optica,Vol.6,No.5,2019,pp.557-562) A micromirror array with a grating fabricated on a moving surface is used to modulate the laser beam.

Electrostatic drive is a common drive method for MEMS micromirror arrays. The difficulty in the design and manufacture of electrostatically driven in-plane moving micromirror arrays mainly comes from the contradiction of maintaining sufficient lateral driving displacement while reducing the size of the micromirror unit.

In order to improve the effect of modulation, the size of the micromirror unit must be reduced and the number of micromirror units must be increased. But on the other hand, optical applications such as lidar require that the maximum displacement of each micromirror unit must be at least greater than half the wavelength of the incident light in order to achieve ±π phase adjustment (Youmin Wang, Guangya Zhou, Xiaosheng Zhang, Kyungmok Kwon, Pierre- A. Blanche, Nicholas Triesualt, Kyoung-Sik Yu, and Ming C. Wu, 2D broadband beamsteering with large-scale MEMS optical phased array, Optica, Vol.6, No.5, 2019, pp.557-562). Since the wavelength of infrared rays exceeds 700nm, the lateral displacement of the micromirror must exceed ±350nm. On the other hand, in order to increase the number of pixels, the side length of each micromirror unit must be reduced to the order of tens of microns. However, in order to achieve a displacement of more than ±350 nm in a structure with a side length of only tens of microns, it poses a great challenge to the design of the supporting beam and the driving structure.

When the in-plane double-end fixed beam is used as the micromirror support structure, at least two double-end support beams are needed to ensure the translational movement of the micromirror in the plane, and the stiffness coefficient is

In the formula, E is Young's modulus, h, b, L are the thickness, width and length of the beam, respectively. From the above formula, it can be obtained that the stubbornness coefficient is inversely proportional to the cube of the length of the support beam, while the length of the MEMS support beam conventionally fabricated in the plane is proportional to the side length of the micromirror unit. Reducing the size of the micromirror unit means reducing the length of the support beam L. In order to avoid a rapid increase in the modulus of elasticity as L decreases, the beam width b must be reduced. Youmin Wang et al. used a support beam with a width of only 300nm to ensure that the displacement of the micromirror can meet the application requirements (Youmin Wang, Guangya Zhou, Xiaosheng Zhang, Kyungmok Kwon, Pierre-A.Blanche, Nicholas Triesualt, Kyoung-Sik Yu, and Ming C. Wu, 2D broadband beamsteering with large-scale MEMS optical phased array, Optica, Vol.6, No.5, 2019, pp.557-562). The 300nm wide beam not only increases the difficulty of lithography, etching and other processes, but also increases the nonlinear effect of displacement because the displacement is greater than the width of the beam, thus increasing the complexity of the control system.

In order to realize the driving displacement greater than the half-wavelength of the incident infrared rays, not only the stubborn coefficient of the supporting beam is required to be small, but also the electrostatic driving force is required to be sufficiently large. Since the electrostatic force decreases rapidly with the increase of the plate gap, and there is a pull-in effect in the normal driving mode, the plate gap must be greater than 3 times the displacement, and it is difficult to obtain sufficient electrostatic force at a lower voltage. The micromirror generally needs to be driven laterally, and its electrostatic force is

Where ε and ε0 are the relative permittivity and the vacuum permittivity, respectively, V is the driving voltage, d0 is the plate gap, and n is the number of electrode pairs. In order to obtain sufficient electrostatic force at lower voltages, it is necessary to increase the number of electrode pairs n and decrease d0. The number n of electrode pairs is obviously also limited by the size of the micromirror unit. Youmin Wang et al. adopted a plate gap with a width of only 300nm, and increased the number of electrode pairs through narrow electrodes (Youmin Wang, Guangya Zhou, Xiaosheng Zhang, Kyungmok Kwon, Pierre-A.Blanche, Nicholas Triesualt, Kyoung-Sik Yu, and Ming C. Wu, 2D broadband beamsteering with large-scale MEMS optical phase array, Optica, Vol.6, No.5, 2019, pp.557-562). The narrow gap not only puts high requirements on the photolithography and etching process, but also requires that the roughness of the sidewall formed by etching must be significantly smaller than the size of the gap.

Contents of the invention

This application proposes a micromirror structure in which beams are perpendicular to the surface of the silicon wafer. The side view of the micromirror structure is shown in Figure 1 and described as follows:

The front side of the substrate wafer 101 is the first surface, and the back side is the second surface. The micromirror 104 is supported by a support beam 103 perpendicular to the surface of the silicon wafer. The support beam 103 is embedded in the hole opened on the substrate wafer 101 and is anchored on the substrate wafer 101 through the fixing layer 102 on the second surface. . The micromirrors 104, the support beams 103 and the fixed layer 102 on the second surface are all made of polysilicon. The micromirror 104 is parallel to the surface of the substrate wafer 101 . An optical structure 107 can be fabricated on the surface of the micromirror 104, and the optical structure 107 can be a grating, a nano-optical structure, or the like. The specific material and structure of the optical structure 107 are not the focus of this application, and will not be described in detail here. The present application only requires that the optical structure 107 be able to withstand the corrosion process of the release structure. Between the fixed layer 102 on the second surface and the substrate wafer 101 is possible with or without the second second insulating layer 1066 . When there is no second second insulating layer 1066 , the fixed layer 102 on the second surface is connected to the same potential as the substrate wafer 101 .

The first driving electrode 121, the second driving electrode 122 and the shielding electrode 123 are made on the first surface side of the substrate wafer 101, and the first driving electrode 121, the second driving electrode 122 and the shielding electrode 123 are made of the same layer of material , can be monocrystalline silicon or polycrystalline silicon material. The fluctuations of the upper surfaces of the first driving electrode 121 , the second driving electrode 122 and the shielding electrode 123 are less than 10 nm. The doping type of the first driving electrode 121, the second driving electrode 122, the micromirror 104, the support beam 103 and the fixed layer 102 on the second surface are the same, which is denoted as the first doping type, and the first doping type can be selected arbitrarily , that can be P-type or N-type. The doping type of the shielding electrode 123 is opposite to the first doping type, and is recorded as the second doping type, that is, when the first doping type is P-type, the second doping type is N-type, and when the first doping type is When N-type, the second doping type is P-type. There is a PN junction between the shielding electrode 123 and the first driving electrode 121 and the second driving electrode 122 , and the PN junction is always in a reverse bias state during operation, that is, the voltage of the N region is higher than the voltage of the P region. The upper surfaces of the first driving electrodes 121 , the second driving electrodes 122 and the shielding electrodes 123 cover the first insulating layer 105 , and the second insulating layer 106 may or may not be formed on the lower surfaces. When there is a second insulating layer 106 between the first driving electrode 121 , the second driving electrode 122 , the shielding electrode 123 and the substrate wafer 101 , the doping type of the substrate wafer 101 is not limited. When there is no second insulating layer 106 between the first driving electrode 121, the second driving electrode 122, the shielding electrode 123 and the substrate wafer 101, the doping type of the substrate wafer 101 is the second doping type, which is different from the first There is a PN junction between the driving electrode 121 and the second driving electrode 122 , and the PN junction is always in a reverse bias state during operation.

There is a second preset gap 112 between the micromirror 104 and the first insulating layer 105, and there is a first preset gap 111 between the support beam 103 and the substrate wafer 101, so the micromirror 104 can be parallel to the surface of the substrate wafer 101 One-dimensional or two-dimensional motion in the plane. The thickness of the second preset gap 112 is in the range of 10 nm to 3 microns. The width of the first preset gap 111 is greater than the working wavelength and less than or equal to 3 microns. The region near the connection point connected with the support beam 103 on the micromirror 104 is the first region. In order to avoid the influence of unevenness that may occur near the connection point of the support beam 103 and the micromirror 104 on the lateral movement of the micromirror, in the first region The gap between the mirror 104 and the first insulating layer 105 forms a third preset gap 113 , and the thickness of the third preset gap 113 is equal to the width of the first preset gap 111 .

The shielding electrode 123 is located directly below the micromirror 104 , and the first driving electrode 121 and the second driving electrode 122 are arranged on both sides of the micromirror 104 , as shown in FIG. 2 in a top view. The polarity of the driving voltage needs to ensure that the PN junction between the shielding electrode 123 and the first driving electrode 121 and the second driving electrode 122 is in a reverse bias state. When the first doping type is P-type and the second doping type is N-type, the driving voltage applied to the first driving electrode 121 and the second driving electrode 122 is lower than the voltage on the shielding electrode 123, that is, the voltage relative to the shielding electrode 123 is used. The electrode 123 has a negative voltage as a driving voltage. When the first doping type is N-type and the second doping type is P-type, the driving voltage applied to the first driving electrode 121 and the second driving electrode 122 is higher than the voltage on the shielding electrode 123, that is, the voltage relative to the shielding electrode 123 is used. The electrode 123 has a positive voltage as a driving voltage.

Preferably, in order to increase the electrostatic force, the micromirror 104, the first driving electrode 121, and the second driving electrode 122 can adopt a structural design as shown in FIG. 3 in a top view. The micromirror 104 adopts a comb structure. That is, one or more notches are respectively provided on both sides of the micromirror 104 , and the positions of the notches on both sides are symmetrical, forming a structure similar to a comb with teeth on both sides. The first driving electrodes 121 are located on one side of the comb teeth and connected together, and the second driving electrodes 122 are located on the other side of the comb teeth and connected together. The optical structure 107 is not shown in FIG. 3 . In order to improve the filling rate of the optical structure, the optical structure 107 can be made into a rectangle. The top view is shown in FIG.

In order to realize the above structure, the following technological process is proposed:

Fabricate the second insulating layer 106 and the first polysilicon layer on the substrate wafer 101, and dope the first polysilicon layer, the doping type is the second doping type, and the doping concentration is lower than the first The doping concentration of the driving electrode 121 and the second driving electrode 122 . The first polysilicon layer is used to form the driving electrode layer 120 . The second insulating layer 106 and the driving electrode layer 120 need to be able to withstand the subsequent sacrificial layer etching process. This step of the process can also be omitted, in which case the substrate wafer 101 needs to be a silicon wafer of the second doping type.

Blind vias 108 are formed, which pass through the second insulating layer 106 and the driving electrode layer 120 and terminate within the substrate wafer 101 . The depth of the blind hole 108 is approximately equal to the length of the support beam 103, and the cross-sectional shape in the plane of the substrate wafer 101 can be rectangular, square, circular, etc., and the dimension in the plane of the substrate wafer 101 is equal to that of the support beam 103 in The in-plane dimension plus twice the width of the second gap 13 . The completed profile is shown in Figure 6.

The first insulating layer 105 is deposited and fabricated, and the cross-section after completion is shown in FIG. 7 . The first insulating layer 105 needs to be able to withstand the subsequent sacrificial layer etching process.

Etching is carried out from the second surface of the substrate wafer 101, exposing the bottom of the first insulating layer 105 in the blind hole 108, the etching depth is approximately equal to the thickness of the substrate wafer 101 minus the depth of the blind hole 108, and the cross-section after completion As shown in Figure 8.

Dry etching is performed from the second surface of the substrate wafer 101 to remove the insulating layer at the bottom of the blind hole 108 , and the completed section is shown in FIG. 9 .

The first sacrificial layer 131 is evenly deposited, and the first sacrificial layer 131 evenly covers the front and back surfaces of the substrate wafer 101 and the inner wall of the through hole. The thickness of the first sacrificial layer 131 is equal to the width of the first preset gap 111 minus the second preset gap. The thickness of the gap 112 is set, and the completed section is shown in FIG. 10 .

Photolithography, etch the first sacrificial layer 131 on the first surface side of the substrate wafer 101, etch the sacrificial layer other than the third preset gap 113 on the first surface side, and then uniformly deposit the second sacrificial layer 132, the second The sacrificial layer 132 uniformly covers the first surface and the second surface on both sides of the substrate wafer 101 and the inner wall of the through hole. The thickness of the second sacrificial layer 132 is equal to the thickness of the second preset gap 112. The completed cross-section is shown in FIG. 11 shown.

Dry etching removes the first sacrificial layer 131 and the second sacrificial layer 132 on the second surface of the substrate wafer 101, and uniformly deposits the second polysilicon layer to form the fixed layer 102, support beams 103 and micromirrors 104, the second Two polysilicon layers fill the space in the through hole to form the support beam 103. In order to ensure complete filling, a low pressure chemical vapor deposition (Low Pressure Chemical Vapor Deposition, LPCVD) process must be used, and the polysilicon layer must be doped while depositing. is the first doping type (in-situ doping). The completed section is shown in Figure 12.

Photoetching and etching the second polysilicon layer on one side of the first surface to form a micromirror 104 , and continuing to etch to remove the exposed second sacrificial layer 132 . The completed cross section is shown in FIG. 13 .

Photolithography, ion implantation and thermal diffusion form the first drive electrode 121 and the second drive electrode 122. Since the size and thickness of the micromirror 104 are much greater than the depth of ion implantation, the first drive electrode 121, the second drive electrode 122 and the micromirror 104 achieve self-alignment. The completed section is shown in Figure 14.

Fabricate the optical structure 107 and metal wires, etch and remove the first sacrificial layer 131 and the second sacrificial layer 132 to release the structure, and make the structure as shown in FIG. 1 to complete the fabrication.

This application has the following advantages:

The micromirror 104 is supported by a support beam 103 perpendicular to the surface of the silicon wafer. The stiffness coefficient of the support beam 103 in the vertical direction is much larger than that in the in-plane direction, and the ability to resist the electrostatic pull-in effect in the vertical direction is strong. Moreover, the shielding electrode 123 and the micromirror 104 always maintain the same potential, which reduces the electrostatic force in the vertical direction. Therefore, the second preset gap 112 can be narrowed to the nanometer level to increase the lateral electrostatic driving force, thereby reducing the unit size while ensuring the lateral displacement.

Since the first driving electrode 121 , the second driving electrode 122 and the shielding electrode 123 are made of the same layer of material, a flat upper surface can be realized, and the fluctuation of the upper surface is less than 10 nm. This feature enables the gap 11 to be reduced to the nanometer scale to increase the lateral electrostatic driving force, thereby reducing the unit size while ensuring the lateral displacement.

Using the process described in this application, the support beam 103 buried in the wafer and perpendicular to the surface of the wafer can be realized. The length of the beam is no longer limited by the side length of the unit in the plane, and the support beam 103 can be reduced by increasing the length of the beam Stubborn coefficient in the horizontal plane, so as to ensure that the lateral displacement meets the application requirements.

The self-alignment process of the driving electrodes and the micromirrors 104 reduces process errors and can increase the number of electrode pairs.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

Fig. 1 is the micromirror structure schematic diagram of an embodiment of the present application;

Fig. 2 is the top view of the micromirror structure of an embodiment of the present application;

FIG. 3 is a schematic diagram of a structure of a driving electrode layer according to an embodiment of the present application;

Fig. 4 is the perspective view of the micromirror structure of an embodiment of the present application;

Fig. 5 is the micromirror structure schematic diagram of an embodiment of the present application;

FIG. 6 is a schematic structural diagram of a blind hole of an embodiment of the present application after fabrication;

FIG. 7 is a schematic structural view of the first insulating layer of an embodiment of the present application after fabrication;

Fig. 8 is a schematic structural diagram of an embodiment of the present application after the second surface is corroded;

FIG. 9 is a schematic structural diagram of an embodiment of the present application after the through hole is fabricated;

FIG. 10 is a schematic structural diagram of an embodiment of the present application after depositing the first sacrificial layer;

FIG. 11 is a schematic structural diagram of an embodiment of the present application after depositing a second sacrificial layer;

FIG. 12 is a schematic structural diagram of an embodiment of the present application after the polysilicon layer is deposited;

Fig. 13 is the structural schematic diagram after the micromirror of an embodiment of the present application is made;

Fig. 14 is a schematic structural diagram of the micromirror structure prepared in one embodiment of the present application;

Fig. 15 is the structural schematic diagram after the micromirror of an embodiment of the present application is made;

FIG. 16 is a schematic structural diagram of the driving electrode of an embodiment of the present application after fabrication;

Fig. 17 is a schematic structural diagram of the micromirror structure prepared in one embodiment of the present application;

The accompanying drawings are supplemented as follows:

101-substrate wafer; 102-fixed layer; 103-support beam; 104-micromirror; 105-first insulating layer; 106-second insulating layer; 107-optical structure; 108-blind hole; 111-first 112-second preset gap; 113-third preset gap; 120-drive electrode layer; 121-first drive electrode; 122-second drive electrode; 123-shield electrode; 131-first sacrifice layer; 132 - second sacrificial layer.

Detailed ways

The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Apparently, the described embodiments are only some of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of this application.

Reference herein to "one embodiment" or "an embodiment" refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present application. In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "top", "bottom" etc. is based on the orientation or positional relationship shown in the drawings, and is only for It is convenient to describe the application and simplify the description, but not to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and thus should not be construed as limiting the application. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of these features. Also, the terms "first", "second", etc. are used to distinguish similar items and not necessarily to describe a specific order or sequence. It is to be understood that the data so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein can be practiced in sequences other than those illustrated or described herein.

Embodiment one:

A P-type monocrystalline silicon wafer is used as the substrate wafer 101, and the following manufacturing process is adopted:

Step S1: Form the second insulating layer 106 and the first polysilicon layer on the P-type monocrystalline silicon wafer by LPCVD, and perform P-type doping on the driving electrode layer 120, and the first polysilicon layer is used to form the driving electrode Layer 120. The second insulating layer 106 is made of low-stress silicon nitride produced by LPCVD.

Step S2: Deep reactive ion etching is used to form the blind hole 108, the blind hole passes through the second insulating layer 106 and the driving electrode layer 120 and terminates in the silicon wafer, and the aspect ratio is controlled within 25:1.

Step S3: forming the first insulating layer 105 by LPCVD deposition, and the first insulating layer 105 is made of low-stress silicon nitride produced by LPCVD.

Step S4: Etching from the second surface of the silicon wafer to expose the bottom of the first insulating layer 105 in the blind hole 108 , the etching depth is approximately equal to the thickness of the silicon wafer minus the depth of the blind hole 108 .

Step S5: Perform dry etching from the second surface of the silicon wafer to remove the silicon nitride insulating layer at the bottom of the blind hole 108 .

Step S6: uniformly depositing the first sacrificial layer 131, the thickness of the first sacrificial layer 131 is equal to the width of the first preset gap 111 minus the thickness of the second preset gap 112, the first sacrificial layer 131 adopts TEOS deposited by LPCVD oxide layer.

Step S7: photolithography, etch the first sacrificial layer 131 on the first surface side of the substrate wafer 101, etch and remove the sacrificial layer other than the third preset gap 113 on the first surface side, and then uniformly deposit the second sacrificial layer 132 , the thickness of the second sacrificial layer 132 is equal to the thickness of the second preset gap 112 , and the second sacrificial layer 132 is made of phosphosilicate glass PSG deposited by LPCVD.

Step S8: dry etching to remove the first sacrificial layer 131 and the second sacrificial layer 132 on the second surface of the substrate wafer 101, and depositing the second polysilicon layer by LPCVD, the second polysilicon layer adopts a layer of phosphorus A composite layer of heavily doped low-stress polysilicon and a layer of ordinary low-stress polysilicon, and uniform phosphorus doping can be achieved in the polysilicon layer after thermal annealing.

Step S9 : photoetching and etching the second polysilicon layer on the first surface side to form the micromirror 104 , and continue etching to remove the exposed second sacrificial layer 132 .

Step S10: Photolithography, phosphorous ion implantation and thermal diffusion to form N-type doped first driving electrodes 121 and second driving electrodes 122. Since the size and thickness of the micromirror 104 is much greater than the depth of ion implantation, the first driving electrodes 121, The second driving electrode 122 is self-aligned with the micromirror 104 . The dosage of phosphorus ion implantation ensures that the first driving electrode 121 and the second driving electrode 122 are inverted to form N-type doping, and the shielding electrode 123 is still P-type doping.

Step S11: Fabricate the optical structure 107 and metal leads, remove the first sacrificial layer 131 and the second sacrificial layer 132 by hydrofluoric acid vapor etching to release the structure, and make the structure as shown in FIG. 1 to complete the fabrication.

When the micromirror is working, the N-type doped micromirror, the P-type doped silicon substrate, and the shielding electrode are connected to the ground potential, and a negative driving voltage is applied to the P-type driving electrode to realize the lateral drive of the micromirror. At the same time, ensure that the PN junction between the driving electrode and the shielding electrode is reverse-biased.

Embodiment two:

The difference between the second embodiment and the first embodiment is that the second insulating layer 106 and the first polysilicon layer are not formed. A P-type monocrystalline silicon wafer is adopted, and the manufacturing process is to omit the step S1 in the first embodiment, and the remaining steps are the same, and the difference in the process is only that step S10 is changed to photolithography, phosphorus ion implantation and thermal diffusion in the P-type monocrystalline silicon wafer. N-type doped first driving electrodes 121 and second driving electrodes 122 are formed in the crystalline silicon substrate. The cross-sectional view after step S9 is completed is shown in FIG. 15 , the cross-sectional view after step S10 is completed is shown in FIG. 16 , and the cross-sectional view of the fabricated structure is shown in FIG. 17 .

When the micromirror is working, the P-type silicon substrate under the micromirror is directly used as a shielding electrode, and the N-type doped micromirror and the P-type doped silicon substrate are grounded, and a negative voltage is applied to the P-type driving electrode. The driving voltage ensures the reverse bias of the PN junction between the driving electrode and the silicon substrate while realizing the lateral driving of the micromirror.

The above descriptions are only preferred embodiments of the application, and are not intended to limit the application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the application shall be included in the protection of the application. within range.

Claims (12)

1. A micromirror structure, characterized in that it comprises: a substrate wafer (101), a driving electrode layer (120), a first insulating layer (105), a support beam (103), a fixed layer (102) and a micromirror mirror(104); The substrate wafer (101) includes an opposite first surface and a second surface, and the driving electrode layer (120) is arranged on the first surface; The substrate wafer (101) and the driving electrode layer (120) are provided with through holes, and the through holes sequentially pass through the driving electrode layer (120), the first surface and the second surface ; The first insulating layer (105) is disposed on the surface of the driving electrode layer (120) away from the substrate wafer (101) and the inner wall of the through hole; The support beam (103) includes a first end and a second end, the first end is connected to the fixed layer (102) through the through hole, and the connection between the support beam (103) and the through hole There is a first preset gap between (111); The fixing layer (102) is arranged on the second surface, and the fixing layer (102) is used for fixing the support beam (103); The driving electrode layer (120) is provided with a first driving electrode (121), a second driving electrode (122) and a shielding electrode (123), and the shielding electrode (123) is arranged on the first driving electrode (121) ) and the second driving electrode (122); The doping type of the first driving electrode (121) and the second driving electrode (122) is the first doping type, the doping type of the shielding electrode (123) is the second doping type, the The first doping type is opposite to the second doping type; a PN junction exists between the first driving electrode (121) and the shielding electrode (123), and a PN junction exists between the second driving electrode (122) and the A PN junction exists between the shielding electrodes (123); The micromirror (104) is arranged on the second end, there is a second preset gap (112) between the micromirror (104) and the first insulating layer (105), and the micromirror ( 104) A surface close to the substrate wafer (101) is parallel to a surface of the first insulating layer (105) away from the substrate wafer (101). 2. micromirror structure according to claim 1, it is characterized in that, described driving electrode layer (120) has the lowest point relative to the surface of described micromirror, take the place plane of described lowest point as reference plane, described driving The distance from the highest point on the surface of the electrode layer (120) to the reference plane is 0-10 nm. 3. The micromirror structure according to claim 2, characterized in that, the material of the micromirror (104), the support beam (103) and the fixed layer (102) is polysilicon; and/or, The first driving electrode (121), the second driving electrode (122) and the shielding electrode (123) are made of the same material, and the first driving electrode (121), the second driving electrode (122) and The material of the shielding electrode (123) is single crystal silicon or polycrystalline silicon. 4. The micromirror structure according to claim 3, characterized in that, the micromirror (104) includes opposite first sides and second sides, at least one notch is provided on the first side, and the first side At least one notch is provided on the two sides, the notch on the first side is set opposite to the notch on the second side, and the drive electrode layer (120) corresponding to the position of the notch on the first side is provided with There is a first driving electrode (121), and a second driving electrode (122) is provided on the driving electrode layer (120) corresponding to the position of the notch on the first side. 5. The micromirror structure according to claim 4, characterized in that, the size of the first preset gap (111) is greater than the working wavelength of the micromirror structure and less than 3 μm; and/or, The size of the second preset gap (112) is 10-3000nm. 6. The micromirror structure according to claim 1, characterized in that, a second insulating layer (106) is also provided between the driving electrode layer (120) and the substrate wafer (101); and/or or, A third insulating layer is also provided between the fixing layer (102) and the second surface. 7. The micromirror structure according to claim 1, characterized in that, the micromirror structure further comprises an optical structure (107), and the optical structure (107) is arranged at a position where the micromirror (104) is far away from the substrate On the surface of the bottom wafer (101), the optical structure is a grating or a nano-optical structure. 8. A micromirror structure, characterized by comprising: a substrate wafer (101), a first insulating layer (105), a support beam (103), a fixed layer (102) and a micromirror (104); The substrate wafer (101) includes opposite first and second surfaces; The substrate wafer (101) is provided with through holes, and the through holes sequentially pass through the first surface and the second surface; The first insulating layer (105) is disposed on the first surface and the inner wall of the through hole; The support beam (103) includes a first end and a second end, the first end is connected to the fixed layer (102) through the through hole, and the connection between the support beam (103) and the through hole There is a first preset gap between (111); The fixing layer (102) is arranged on the second surface, and the fixing layer (102) is used for fixing the support beam (103); The micromirror (104) is arranged on the second end, there is a second preset gap (112) between the micromirror (104) and the first insulating layer (105), and the micromirror ( 104) A surface close to the substrate wafer (101) is parallel to a surface of the first insulating layer (105) away from the substrate wafer (101); The area on the substrate wafer (101) corresponding to the micromirror (104) is a shielding electrode (123), and there is a gap between the substrate wafer (101) and the first insulating layer (105). A first driving electrode (121) and a second driving electrode (122) are provided, and the shielding electrode (123) is arranged between the first driving electrode (121) and the second driving electrode (122); The doping type of the first driving electrode (121), the second driving electrode (122), the micromirror (104), the support beam (103) and the fixed layer (102) is the first doping type; the doping type of the substrate wafer (101) and the shielding electrode (123) is a second doping type; the first doping type is opposite to the second doping type; A PN junction exists between the first driving electrode (121) and the shielding electrode (123), and a PN junction exists between the second driving electrode (122) and the shielding electrode (123); the substrate A PN junction exists between the wafer (101) and the first driving electrode (121), and a PN junction exists between the substrate wafer (101) and the second driving electrode (122). 9. a preparation method of micromirror structure, is characterized in that, described method is used for preparing the micromirror structure as any one of claim 1-7, and described method comprises: A second insulating layer (106) is fabricated on a substrate wafer (101), the substrate wafer (101) includes opposite first surfaces and second surfaces, and the second insulating layer (106) is fabricated on the on the first surface; making a driving electrode layer (120) on the second insulating layer (106); Doping the driving electrode layer (120), the doping type is the second doping type; A blind hole (108) with a predetermined depth is made on the substrate wafer (101), and the blind hole (108) sequentially penetrates the driving electrode layer (120), the second insulating layer (106) and the first surface; forming a first insulating layer (105) on the inner wall of the driving electrode layer (120) and the blind hole (108); processing the first insulating layer (105) on the second surface and the bottom of the blind hole (108), so that the blind hole (108) forms a through hole; depositing a sacrificial layer on the first insulating layer (105) and on the inner wall of the through hole; Fabricating a fixed layer (102), a support beam (103) and a micromirror layer on the second surface, the through hole and the sacrificial layer respectively; Etching the micromirror layer to form a micromirror (104); Ion implantation is performed on the driving electrode layer (120), and a first driving electrode (121) and a second driving electrode (122) are formed on the driving electrode layer (120); the ion implantation region is the driving electrode layer ( In at least a part of the region in 120) other than the region corresponding to the micromirror (104), the ion implantation depth is smaller than the thickness of the micromirror (104); fabricating an optical structure (107) on the micromirror layer; removing the sacrificial layer to obtain the micromirror structure. 10. The preparation method according to claim 9, characterized in that, the fixing layer (102), support beams (103) and micro Mirror layers, including: removing the sacrificial layer on the second surface by dry etching; uniformly depositing a polysilicon layer on the second surface, in the through hole, and on the first insulating layer (105) by low-pressure chemical vapor deposition, and simultaneously doping the polysilicon layer with a first doping type; Wherein, the polysilicon layer on the second surface forms the fixed layer (102), the polysilicon layer in the through hole forms the support beam (103), and the first insulating layer (105) The polysilicon layer above forms the micromirror layer. 11. The preparation method according to claim 10, characterized in that, the first insulating layer (105) on the second surface and the bottom of the blind hole (108) is treated so that the Blind holes (108) form through holes and include: etching the second surface to expose the bottom of the first insulating layer (105) in the blind hole (108); The first insulating layer (105) at the bottom of the blind hole (108) is removed to form a through hole. 12. a preparation method of micromirror structure, is characterized in that, described method is used for preparing micromirror structure as claimed in claim 8, and described method comprises: A blind hole (108) with a predetermined depth is fabricated on the substrate wafer (101), wherein the doping type of the substrate wafer (101) is the second doping type, and the substrate wafer (101) ) comprising opposing first and second surfaces, said blind hole (108) being formed on said first surface; making a first insulating layer (105) on the first surface and the inner wall of the blind hole (108); processing the first insulating layer (105) on the second surface and the bottom of the blind hole (108), so that the blind hole (108) forms a through hole; depositing a sacrificial layer on the first insulating layer (105) and on the inner wall of the through hole; Fabricating a fixed layer (102), a support beam (103) and a micromirror layer on the second surface, the through hole and the sacrificial layer respectively; Etching the micromirror layer to form a micromirror (104); performing ion implantation on the substrate wafer (101), forming a first driving electrode (121) and a second driving electrode (122) on the substrate wafer (101); the ion implantation region is the first In at least a partial area on the surface other than the area corresponding to the micromirror (104), the ion implantation depth is less than the thickness of the micromirror (104); fabricating an optical structure (107) on the micromirror layer; removing the sacrificial layer to obtain the micromirror structure.

Images