CN115784143A - Self-aligned polycrystalline silicon and monocrystalline silicon hybrid MEMS vertical electrode and manufacturing method thereof - Google Patents
Self-aligned polycrystalline silicon and monocrystalline silicon hybrid MEMS vertical electrode and manufacturing method thereof Download PDFInfo
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Abstract
The invention discloses a self-aligned polycrystalline silicon and monocrystalline silicon hybrid MEMS vertical electrode and a manufacturing method thereof, wherein the polycrystalline silicon and monocrystalline silicon hybrid MEMS vertical electrode is formed by etching a plurality of deep grooves on a monocrystalline silicon wafer, oxidizing the monocrystalline silicon wafer and depositing polycrystalline silicon, the monocrystalline silicon has perfect lattice and good physical property, and can be used for manufacturing a movable electrode and a functional structure; the polycrystalline silicon is fixed on the monocrystalline silicon fixing column to be used as a fixed electrode. The monocrystalline silicon movable electrode and the polycrystalline silicon fixed electrode are determined by a pattern of one-time photoetching/etching to realize self-alignment, and the electrode distance in the horizontal direction between the electrodes is determined by the thickness of a silicon dioxide layer.
Description
Technical Field
The invention belongs to the technical field of microelectronic wafer processing, and particularly relates to a self-aligned polycrystalline silicon and monocrystalline silicon hybrid MEMS vertical electrode and a manufacturing method thereof.
Background
A MEMS (Micro-Electro-Mechanical System) chip generally has a movable structure, a fixed structure and a spring structure for supporting the movable structure, a fixed electrode, and a cavity for providing a free moving space for the movable structure. Some MEMS chip structures require a driving structure to provide motion power for the MEMS moveable structure, and the power includes electrostatic force, magnetic force, fluid pressure, piezoelectric force, etc., and the most widespread is electrostatic force, such as MEMS oscillator, MEMS gyroscope, resonant MEMS accelerometer, MEMS micro-mirror, MEMS optical attenuator, resonant MEMS pressure sensor, MEMS actuator, etc. all use electrostatic force mechanical driving structure. Generally, the electrostatic force is provided by the voltage difference between the fixed electrode and the movable electrode, and the corresponding electrode on the movable structure is driven by the parallel plate electrode or the interdigital electrode, so that the movable structure generates controllable motion. The moving direction of the movable structure can be horizontal or vertical according to the functional requirements of the MEMS device, the driving structure in the horizontal direction is easy to process, and the processing technology of the driving structure in the vertical direction is complex. The parallel plate electrode has small driving distance, poor linearity and low driving efficiency per unit area, so that some MEMS devices, such as optical attenuators, micro mirrors and some three-axis gyroscopes, need to use a comb electrode driving structure in the vertical direction. In addition, signals of some MEMS sensors sense signals through displacement of a movable structure, such as a MEMS gyroscope, a MEMS accelerometer, and the like, and a vertical electrode structure is required in chip design.
The vertical electrode structure shown in fig. 1 (the vertical electrodes described below refer to an electrode structure in which the MEMS movable electrode moves in a direction perpendicular to the MEMS chip substrate) is the easiest to process, and the movable electrode 173 and the fixed electrode 171 form a height difference D at the upper portion, have no height difference at the lower portion, and have an electrode pitch W 0 The movable electrode 173 is movable in the vertical direction, and when the structure is used for driving, the movable electrode can move only in one direction in the vertical direction; when in useWhen the structure is used for detection, only one-way signals can be detected, and the linearity is poor. The vertical electrode structure shown in fig. 2 is widely applied to products such as MEMS optical attenuators and MEMS micro mirrors, the movable electrode 273 is located above the fixed electrode 271, the two are not overlapped in the horizontal direction, the distance difference in the vertical direction is D, because the structure is formed by the secondary photolithography alignment/etching process or the double single crystal silicon wafer bonding process, the electrode distance W in the horizontal direction is considered to align the precision 1 And W 2 The driving force is not always equal and is inversely proportional to the electrode spacing, resulting in a small driving force, and the structure has a complicated manufacturing process, the movable electrode 273 can move in the vertical direction, and when the structure is used for driving, the movable electrode can only move in a downward single direction, and the linearity is poor, and thus it cannot be used for precise detection. The structure shown in fig. 2 is formed by the MEMS device structure design and processing methods described in patents CN11718906, CN103086316, CN113820851, CN113820852, US10268037B2, US10551613B2, etc.
Patents US10077184B2, US20050013087A1 describe adding materials with different thermal expansion coefficients to the spring, causing the spring to tilt in the vertical direction, creating a difference in height of the different electrodes in the vertical direction. This technique has poor repeatability of processing accuracy and poor temperature characteristics of the fabricated devices. The patents US7469588B2 and US9493344B2 form a fully suspended vertical sensing electrode by means of the electrical isolation of the interdigital electrode in the vertical direction, and cannot be used for driving in the vertical direction.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a self-aligned polysilicon and monocrystalline silicon hybrid MEMS vertical electrode and a manufacturing method thereof.
In order to solve the technical problem, the invention provides a self-aligned polycrystalline silicon and monocrystalline silicon mixed MEMS vertical electrode which is formed by bonding a monocrystalline silicon movable electrode, a polycrystalline silicon fixed electrode, a cavity, a monocrystalline silicon substrate, a monocrystalline silicon fixed column and an edgeThe polycrystalline silicon fixed electrode is fixed on the monocrystalline silicon fixed column through the silicon dioxide layer and is electrically connected with the monocrystalline silicon fixed column through the contact hole; the monocrystalline silicon fixing column is bonded on the monocrystalline silicon substrate, and an insulating layer is arranged between the monocrystalline silicon fixing column and the monocrystalline silicon substrate; the monocrystalline silicon movable electrode is connected with the MEMS functional structure; the horizontal distance W is formed between the monocrystalline silicon movable electrode and the polycrystalline silicon fixed electrode, the bottom of the monocrystalline silicon movable electrode is lower than that of the polycrystalline silicon movable electrode, and the height difference is D 1 The top of the polysilicon fixed electrode is higher than the monocrystalline silicon movable electrode, and the height difference is D 2 (ii) a A cavity is arranged between the monocrystalline silicon movable electrode and the monocrystalline silicon substrate, and between the polycrystalline silicon fixed electrode and the monocrystalline silicon substrate, so that space is provided for free movement of the monocrystalline silicon movable electrode.
The MEMS functional structure is a reflector, a mass block or a vibrator.
Silicon dioxide is reserved between the polycrystalline silicon fixed electrode and the monocrystalline silicon fixed column to play a role in fixing.
The self-aligned polycrystalline silicon and monocrystalline silicon hybrid MEMS vertical electrode can be used for detecting displacement signals of an MEMS functional structure in the vertical direction and can also be used for driving the MEMS functional structure to move in the vertical direction. When the MEMS functional structure is used as a detection electrode, the displacement of the MEMS functional structure in the vertical direction is measured through the capacitance signal change between the polycrystalline silicon fixed electrode and the monocrystalline silicon movable electrode; when the polycrystalline silicon fixed electrode and the monocrystalline silicon movable electrode are used as driving electrodes, when voltages with different polarities are applied between the polycrystalline silicon fixed electrode and the monocrystalline silicon movable electrode, the monocrystalline silicon movable electrode moves upwards; when a voltage of the same polarity is applied, the single-crystal silicon movable electrode moves downward. The electrode distance W of the invention is determined by the thickness of the oxide layer (silicon dioxide layer), namely, the electrode distance of the invention can be smaller for the MEMS structure layer with the same thickness. When the vertical electrode is used for a driving electrode of an MEMS structure, the driving force in the vertical direction is inversely proportional to the electrode distance W, and the smaller the electrode distance W is, the larger the driving force is; similarly, when the vertical electrode is used for a detection electrode of an MEMS structure, the sensitivity in the vertical direction is inversely proportional to the electrode distance W, and the smaller the electrode distance W is, the larger the sensitivity is; an even greater advantage is also that the electrode spacing W remains constant during the detection processOnly the overlapping area of the monocrystalline silicon movable electrode and the polycrystalline silicon fixed electrode changes, the linearity is good, and the detection range is large; in addition, the height difference D of the monocrystalline silicon movable electrode and the polycrystalline silicon fixed electrode in the vertical direction 1 、D 2 The self-aligned polysilicon and monocrystalline silicon hybrid MEMS vertical electrode is formed by etching, the upper end and the lower end of the self-aligned polysilicon and monocrystalline silicon hybrid MEMS vertical electrode are provided with height differences, the height differences can be adjusted according to design requirements, and the driving force is larger than that of a single-end height difference electrode in consideration of edge effect.
In order to solve the technical problem, the invention also provides a manufacturing method of the self-aligned polysilicon-monocrystalline silicon hybrid MEMS vertical electrode, which comprises the following steps:
(1) Etching monocrystalline silicon on the surface of the monocrystalline silicon wafer through a photoresist mask to form a first cavity, an edge bonding area and a fixed bonding column;
(2) Etching through a photoresist mask in the first cavity to form a deep groove, dividing a monocrystalline silicon wafer into a monocrystalline silicon movable electrode column, a monocrystalline silicon fixed column and an edge region in the horizontal direction by the deep groove, etching on the monocrystalline silicon fixed column to form a first cavity step and a fixed bonding column, and etching the edge region to form an edge step; is divided into a substrate layer and a MEMS structural layer in the vertical direction;
(3) Oxidizing the monocrystalline silicon wafer treated in the step (2) to generate a silicon dioxide layer, and then etching the silicon dioxide layer on the first concave cavity step through a photoresist mask to form a contact hole;
(4) Depositing a polycrystalline silicon layer on the surface of the monocrystalline silicon wafer treated in the step (3) by an in-situ doping CVD method and annealing;
(5) The polycrystalline silicon layer is etched back without a mask, a part of the polycrystalline silicon layer is removed, a polycrystalline silicon second surface is formed, the monocrystalline silicon fixing column and the first surface of the silicon dioxide layer of the marginal area are exposed, and the polycrystalline silicon second surface is lower than the first surface of the silicon dioxide layer;
(6) Covering the monocrystalline silicon fixing column with a photoresist mask, etching the polycrystalline silicon layer, wherein the polycrystalline silicon protected by the photoresist mask is not etched to form a polycrystalline silicon fixing region, the polycrystalline silicon on the edge step is etched to expose silicon dioxide, part of the polycrystalline silicon in the deep groove is etched to form a polycrystalline silicon third surface, the polycrystalline silicon third surface is lower than the first surface of the monocrystalline silicon movable electrode column, and the residual polycrystalline silicon in the deep groove forms a fixed electrode of the MEMS structure layer;
(7) Corroding the silicon dioxide layer on the surface of the monocrystalline silicon wafer processed in the step (6) to expose the first surface of the monocrystalline silicon movable electrode column and the first surface of the edge bonding area; then removing the photoresist mask, corroding and removing the silicon dioxide layer on the surface of the fixed bonding column to expose the first surface of the fixed bonding column to form a structural wafer;
(8) Bonding the structural wafer obtained in the step (7) to a base plate wafer to form a bonded wafer, wherein the base plate wafer consists of a monocrystalline silicon substrate and an insulating layer;
(9) Removing the substrate layer, exposing the silicon dioxide layer on the back of the deep groove, covering the monocrystalline silicon fixing column and the edge bonding region of the bonding wafer by using a photoresist mask, etching monocrystalline silicon, etching the monocrystalline silicon movable electrode column to form a second surface of the monocrystalline silicon movable electrode column, wherein the second surface of the monocrystalline silicon movable electrode column is lower than the second surface of the silicon dioxide layer on the back of the deep groove;
(10) And removing the photoresist on the bonding wafer, corroding the silicon dioxide layer between the polycrystalline silicon layer and the monocrystalline silicon movable electrode column, releasing the monocrystalline silicon movable electrode column to form a monocrystalline silicon movable electrode, and forming a polycrystalline silicon fixed electrode by the polycrystalline silicon in the deep groove.
In the step (3), the monocrystalline silicon wafer can be thermally oxidized firstly, a thin silicon dioxide layer is formed on all the surfaces, and after the thin silicon dioxide layer is corroded, the monocrystalline silicon wafer is thermally oxidized again to form the silicon dioxide layer.
The step (5) can also be: firstly thinning the polysilicon layer until the first concave cavity step is just exposed, then forming a contact hole, then depositing the polysilicon layer for the second time and annealing, and finally thinning the polysilicon layer deposited for the second time.
And (4) in the step (7), the corrosion amount of silicon dioxide between the monocrystalline silicon movable electrode column and the polycrystalline silicon fixed area is larger than that of silicon dioxide between the polycrystalline silicon fixed area and the monocrystalline silicon fixed column.
And (5) silicon dioxide is remained between the polycrystalline silicon fixed electrode and the monocrystalline silicon fixed column in the step (10).
The manufacturing method of the invention forms the polysilicon and monocrystalline silicon mixed vertical comb electrode by etching a plurality of deep grooves on the monocrystalline silicon wafer, oxidizing the monocrystalline silicon wafer and depositing the polycrystalline silicon; the monocrystalline silicon has perfect lattice and good physical property, and is used for manufacturing a movable electrode and a functional structure, and the polycrystalline silicon is fixed on the monocrystalline silicon fixed column to be used as a polycrystalline silicon fixed electrode. The self-aligned polysilicon and monocrystalline silicon mixed MEMS vertical electrode manufactured by the method has the advantages of high dimensional precision, good processing repeatability, good performance consistency and simple processing technology, and the cost is lower because an SOI wafer with high price is not needed.
In the prior art, the electrode spacing is generally formed by a deep silicon etching process, and the aspect ratio of the existing deep silicon etching technology capable of mass production is 30: the aspect ratio is the ratio of the thickness of the MEMS structure layer to the horizontal pitch between the MEMS structures, so that the pitch of the electrodes of the vertical electrodes manufactured by the prior art is limited by the thickness of the MEMS structures, for example, the pitch of the electrodes of the MEMS structure layer with a thickness of 60 μm cannot be smaller than 2 μm. In the present invention, since the electrode distance W is determined by the thickness of the oxide layer (silicon dioxide layer), and is not dependent on the thickness of the MEMS structure, the electrode distance W of the present invention can be 0.5 μm by taking the MEMS structure layer with a thickness of 60 μm as an example. When the vertical electrode is used as a driving electrode of an MEMS structure, the driving force in the vertical direction is inversely proportional to the electrode spacing W, and the smaller the electrode spacing W is, the larger the driving force is; similarly, when the vertical electrode is used for a detection electrode of an MEMS structure, the sensitivity in the vertical direction is inversely proportional to the electrode distance W, and the smaller the electrode distance W is, the larger the sensitivity is; the method has the advantages that in the detection process, the electrode spacing W is kept unchanged, only the overlapping area of the monocrystalline silicon movable electrode and the polycrystalline silicon fixed electrode is changed, the linearity is good, and the detection range is large; in addition, sheetHeight difference D between crystalline silicon movable electrode and polycrystalline silicon fixed electrode in vertical direction 1 、D 2 The self-aligned polysilicon and monocrystalline silicon hybrid MEMS vertical electrode is formed by etching, the upper end and the lower end of the self-aligned polysilicon and monocrystalline silicon hybrid MEMS vertical electrode are provided with height differences, the height differences can be adjusted according to design requirements, and the driving force is larger than the single-ended height difference electrode in consideration of edge effect, so that the self-aligned polysilicon and monocrystalline silicon hybrid MEMS vertical electrode manufactured by the method has the advantages of strong driving force, large driving stroke and good linearity.
Drawings
Fig. 1 is a schematic view of a conventional vertical electrode structure.
Fig. 2 is a schematic diagram of another conventional vertical electrode structure.
Fig. 3-14 are flow charts of methods of fabricating self-aligned polysilicon-single crystal silicon hybrid MEMS vertical electrodes according to a first embodiment.
Fig. 15 is an enlarged view of a dotted line portion in fig. 14.
Fig. 16 is a schematic diagram of a vertical electrode unit as a core unit applied to a MEMS device.
Fig. 17 is a cross-sectional view of a MEMS wafer after removal of an inter-electrode oxide layer in accordance with a second embodiment.
Detailed Description
The invention is further illustrated by the following figures and examples.
Example one
A manufacturing method of a self-aligned polysilicon-monocrystalline silicon hybrid MEMS vertical electrode comprises the following steps:
(1) A heavily doped single crystal silicon wafer 12 is used as a single crystal silicon layer of the MEMS structure, the resistivity is 0.001-0.1 omega CM, and the thickness of the wafer is 300-800 mu m. Through the processing procedures of gluing, exposing, developing, etching, removing glue, cleaning and the like, a first cavity 21, an edge bonding area 23 and a fixed bonding column 25 are formed on the surface of the monocrystalline silicon wafer 12, the depth of the first cavity 21 is 0.5-50 μm, and the depth determines the movable space of the monocrystalline silicon movable electrode in the vertical direction, as shown in fig. 3.
(2) Forming a deep groove 27 in the first cavity 21 through the processing procedures of gluing, exposing, developing, deep silicon etching, removing glue, cleaning and the like, wherein the depth of the deep groove is 1-200 mu m, at the moment, the monocrystalline silicon wafer 12 is horizontally divided into a monocrystalline silicon movable electrode column 32, a monocrystalline silicon fixed column 34 and an edge region 36, a first cavity step 21a and a fixed bonding column 25 are formed on the monocrystalline silicon fixed column 34, and an edge step 21b is formed on the edge region 36; the fixed bond posts 25 are located on the single crystal silicon fixed posts 34 and the edge bond regions 23 are located on the edge region 36. The monocrystalline silicon wafer 12 is divided in the vertical direction into a monocrystalline silicon substrate layer 15 and a MEMS structure layer 17, as shown in fig. 4.
(3) And thermally oxidizing the single crystal silicon wafer etched in the deep trench 27 shown in fig. 4 to form a uniform silicon dioxide layer 39 with a thickness of 0.5-5 μm on the first surface 17a of the MEMS structure layer 17, as shown in fig. 5.
In order to improve the quality of the side wall of the MEMS structure layer 17, for example, to reduce the roughness of the wave formed by the Bosch deep silicon etching process, the single crystal silicon wafer 12 may be thermally oxidized first to form a silicon dioxide layer with a thickness of 1 to 5 μm on all surfaces, and after the silicon dioxide layer is etched away by HF acid, the single crystal silicon wafer 12 may be thermally oxidized again to form the silicon dioxide layer 39.
(4) And forming a contact hole 38 on the first cavity step 21a of the monocrystalline silicon fixing column 34 on the surface of the monocrystalline silicon wafer shown in fig. 5 through the processing procedures of glue spraying, exposure, development, etching of the silicon dioxide layer 39, glue removal, cleaning and the like, as shown in fig. 6. The pattern of the contact hole 38 may be a rectangular or circular hole chain formed by a plurality of round holes, or a rectangular or circular hole chain formed by a plurality of square holes; or may be a circular or square ring.
(5) Depositing an in-situ (in-situ) doped polysilicon layer 40 on the surface of the single crystal silicon wafer shown in fig. 6 by a CVD (chemical vapor deposition) method, and forming a flat polysilicon first surface 40a by a CMP (chemical mechanical polishing) process, wherein the deep trench 27, the first cavity 21 and the contact hole 38 are filled with the polysilicon layer 40; the polysilicon layer 40 covers all of the silicon dioxide layer 39, with the first polysilicon layer surface 40a being significantly higher than the silicon dioxide layer first surface 39a, as shown in fig. 7.
(6) Using maskless etch-back processes, e.g. CF 4 、SF 6 And (3) uniformly removing a part of the polycrystalline silicon layer 40 by plasma or reactive ion etching process of the gas to form a polycrystalline silicon second surface 40b, as shown in fig. 8, wherein the polycrystalline silicon layer 40 covers the first cavity step 21a, the edge step 21b and the monocrystalline silicon movable electrode column first surface 32a, the contact hole 38 and the monocrystalline silicon movable electrode column 32 are also covered by the polycrystalline silicon layer 40, the polycrystalline silicon layer 40 above the edge bonding region 23 and the fixed bonding column 25 is etched away to expose the silicon dioxide layer first surface 39a, and the polycrystalline silicon second surface 40b is obviously lower than the silicon dioxide layer first surface 39a.
(7) Performing processing procedures such as gluing, exposing, developing and the like on the surface of the monocrystalline silicon wafer shown in fig. 8 to form a photoresist mask 42, wherein the size of the photoresist mask is at least obviously larger than that of the monocrystalline silicon fixed column 34 in one horizontal direction, etching the polycrystalline silicon layer 40 to form a polycrystalline silicon third surface 40c, as shown in fig. 9, the polycrystalline silicon under the protection region of the mask 42 is not etched to form a polycrystalline silicon fixed region 45, the polycrystalline silicon on the edge step 21b is etched to expose the silicon dioxide layer 39, the polycrystalline silicon 40 in the deep trench 27 is partially etched to form a polycrystalline silicon third surface 40c, the polycrystalline silicon third surface 40c is obviously lower than the edge step 21b and the monocrystalline silicon movable electrode column first surface 32a, and the remaining polycrystalline silicon 40 in the deep trench 27 forms a fixed electrode of the MEMS structure layer 17.
(8) Etching the single-crystal silicon wafer shown in fig. 9 with HF acid solution or gaseous HF acid, controlling the etching time, and etching away the silicon dioxide layer 39 outside the mask 42 that is not covered by the polysilicon layer 40 and the silicon dioxide layer 39 partially between the polysilicon layer 40 and the single-crystal silicon movable electrode column 32, so as to facilitate the removal of all the silicon dioxide layer 39 in the subsequent process, release the movable structure, and expose the first surface 32a of the single-crystal silicon movable electrode column and the first surface 23a of the edge bonding region; then removing the photoresist mask 42, continuing to etch with HF acid solution or gaseous HF acid, removing the silicon dioxide layer 39 on the surface of the fixed bonding post 25 to expose the first surface 25a of the fixed bonding post; the silicon dioxide 39 still remains between the polysilicon layer 40 and the single crystal silicon fixing posts 34, resulting in the wafer 50 shown in fig. 10.
(9) Taking a base plate wafer 60, the crystal thereofThe base plate wafer 60 is the same as the monocrystalline silicon wafer 12 and consists of a monocrystalline silicon substrate 62 and an insulating layer 64, wherein the insulating layer 64 is made of thermally grown silicon dioxide and has the thickness of 0.5-3 mu m; the first surface 17a of the MEMS structure layer of the structure wafer 50 and the insulating layer 64 of the bottom plate wafer 60 are subjected to Si-SiO 2 Fusion bonding, bonding the base wafer 60 and the structural wafer 50 together, forms a bonding surface 55 between the first surface 25a of the fixed bonding post and the first surface 23a of the edge bonding region and the insulating layer 64, as shown in fig. 11.
(10) The monocrystalline silicon substrate layer 15 of the wafer after bonding shown in fig. 11 is removed by grinding, CMP, maskless etching, and the like to form the second surface 17b of the MEMS structure layer, exposing the back surface 27a of the deep trench, and the second surface 39b of the silicon dioxide layer on the back surface 27a of the deep trench blocks active reaction components in the etching process, thereby protecting the polycrystalline silicon 40 in the deep trench 27, as shown in fig. 12.
(11) Etching the bonded wafer shown in fig. 12 by the processing procedures of gluing, exposing, developing, etching, removing the glue, cleaning and the like to form a second cavity 66, as shown in fig. 13, the photoresist 68 covers the edge bonding region 23 and the fixed electrode column 34, the two regions are not etched, and the polysilicon 40 in the deep trench 27 is not etched because the second surface 39b of the silicon dioxide layer blocks active reaction components in the etching process; at this time, the single crystal silicon movable electrode column 32 is etched to form a second surface 32b of the single crystal silicon movable electrode column, and the second surface 32b of the single crystal silicon movable electrode column is significantly lower than the back surface 27b of the deep trench.
(12) Removing the photoresist 68 on the bonded wafer shown in fig. 13, cleaning, and then etching the silicon oxide layer 39 with HF solution or gaseous HF until the silicon oxide 39 between the polysilicon layer 40 and the movable single-crystal silicon electrode column 32 is completely removed and separated, so that the movable single-crystal silicon electrode column 32 is released and can move freely to form a movable single-crystal silicon electrode 71; the polysilicon 40 in the deep trench 27 forms a polysilicon fixed electrode 73, as shown in fig. 14; the spacing between the polysilicon fixed electrode 73 and the single-crystal silicon movable electrode 71 is equal to the thickness of the silicon dioxide layer 39; a part of silicon dioxide 39c is reserved between the polycrystalline silicon layer 40 and the monocrystalline silicon fixing column 34 and plays a role in fixing; the insulating layer (silicon dioxide) 64 of the non-bonding region is also etched away in an HF solution or gaseous HF etching process to expose the single crystal silicon substrate 62; the insulating layer 64 remaining after etching, the single-crystal silicon substrate 62 and the first cavity 21 together enclose a chamber 75 to provide a movable space for the single-crystal silicon movable electrode 71.
To more clearly illustrate the vertical comb-teeth electrode structure unit, the dashed frame portion (vertical electrode unit 100) in fig. 14 is enlarged, and as shown in fig. 15, a gap W, that is, an electrode distance in the horizontal direction, is formed between the movable electrode 71 of single crystal silicon and the adjacent fixed electrode 73 of polycrystalline silicon; in the vertical direction, the second surface 32b of the movable electrode 71 of single-crystal silicon is lower than the upper surface of the fixed electrode 73 of polycrystalline silicon, i.e., the fourth surface 40D of polycrystalline silicon, by a height difference D 1 (ii) a The first surface 32a of the movable electrode 71 of single crystal silicon is lower than the lower surface of the fixed electrode 73 of polycrystalline silicon, i.e. the third surface 40c of polycrystalline silicon, by a height difference D 2 ；D 1 And D 2 The movable electrodes 71 may be equal or unequal, and may be freely movable in the vertical direction.
The vertical electrode unit 100 as a core unit can be used in different MEMS device structures, such as MEMS gyroscopes, accelerometers, microscopes, resonators or actuators, etc., as shown in fig. 16, a plurality of polysilicon fixed electrodes 73 constitute a fixed comb electrode group 83 fixed on a single-crystal silicon fixed pillar 34, and a single-crystal silicon fixed pillar surface 34a can be bonded with a signal-deriving cover plate by Si-metal bonding or Si-Si bonding; a plurality of monocrystalline silicon movable electrodes 71 form a movable comb-tooth electrode group 81 and are connected to a movable functional structure 110 of the MEMS device, and the movable functional structure 110 can be a reflector, a mass block, a vibrator or the like; the dashed line around the single-crystal silicon movable electrode 71 indicates that the surface 32b thereof is lower than the single-crystal silicon fixed column surface 34a, the edge bonding region second surface 23b and the surface of the movable functional structure 110 in the vertical direction; the edge bonding area 23 may be used to bond the cover plate protection MEMS structure or may not be bonded to any structure.
The self-aligned polysilicon-single crystal silicon hybrid MEMS vertical electrode manufactured in this example is composed of a single crystal silicon movable electrode 71, a polysilicon fixed electrode 73, and an insulating layer 6, as shown in fig. 14 and 154. The silicon single crystal substrate 62, the cavity 75, the silicon dioxide layer 39, the silicon single crystal fixing column 34 and the edge bonding area 23; the polysilicon fixing electrode 73 is fixed on the single crystal silicon fixing post 34 through the polysilicon fixing region 45 and the residual silicon dioxide 39c, and is electrically connected with the single crystal silicon fixing post 34 through the contact hole 38; the monocrystalline silicon fixing column 34 is fixed on the insulating layer 64 through a bonding process and is not electrically connected with the monocrystalline silicon substrate 62; the monocrystalline silicon movable electrode 71 is connected with a movable functional structure 110 of the MEMS device, such as a reflector, a driving mass, a detection mass or a vibrator; a gap W is formed between the movable electrode 71 and the fixed electrode 73, and the bottom 32a of the movable electrode 71 is lower than the bottom 40c of the fixed electrode 73 by a height difference D 1 (ii) a The top 32b of the movable electrode is lower than the top 40D of the fixed electrode, and the height difference is D 2 (ii) a A cavity 75 is formed between the vertical electrode unit 100 and the single crystal silicon substrate 62 to provide a free movement space for the movable electrode 71; the edge bonding regions 23 provide protection for the MEMS structure.
Example two
After the bonded wafer shown in fig. 13 is formed, the photoresist 68 is retained, and then the silicon oxide layer 39 is etched with an HF solution until the silicon oxide 39 between the polysilicon layer 40 and the movable single-crystal silicon electrode column 32 is completely removed, the two are separated, and then the photoresist 68 is removed and cleaned, as shown in fig. 17, so that the movable single-crystal silicon electrode column 32 is released and can move freely to form a movable single-crystal silicon electrode 71; the polysilicon 40 in the deep trench 27 forms a polysilicon fixed electrode 73; the spacing W between the polysilicon fixed electrode 73 and the single-crystal silicon movable electrode 71 is equal to the thickness of the silicon dioxide layer 39; residual silicon dioxide 39d still remains between the polysilicon 40 and the single crystal silicon fixing post 34, since the photoresist 68 prevents the etching of the silicon dioxide layer 39 under the photoresist in the vertical direction during the etching process of the HF solution, but a part of silicon dioxide is also under-etched by the HF solution in the horizontal direction, obviously, the residual silicon dioxide 39d in the second embodiment is more than the residual silicon dioxide 39c in the first embodiment, and the mechanical strength of the combination of the polysilicon fixing electrode 73 and the single crystal silicon fixing post 34 is higher than that in the first embodiment; the non-bonding region insulating layer (silicon dioxide) 64 is also etched away in the HF solution etching step, exposing the single crystal silicon substrate 62; the insulating layer 64 remaining after etching, the single-crystal silicon substrate 62 and the first cavity 21 together enclose a chamber 75 to provide a movable space for the single-crystal silicon movable electrode 71.
The foregoing is only the preferred embodiment of the present invention. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, several modifications or equivalent substitutions can be made to the technical solution of the present invention, such as: depositing an in-situ doped polysilicon layer 40 on the monocrystalline silicon wafer shown in fig. 5, thinning the polysilicon layer 40 through a CMP process and a back etching process until the first cavity step 21a is just exposed, forming a contact hole 38 through processes of gluing, exposing, developing, etching a silicon dioxide layer 39, removing glue, cleaning and the like, depositing a polysilicon layer for the second time, annealing, thinning the polysilicon layer deposited for the second time through the CMP process and the back etching process, and forming a wafer structure shown in fig. 8; the method can avoid the great height difference between the deep trench 27 and the first cavity step 21a when the contact hole 38 is formed, and reduce the difficulty of the photoetching process. These can also achieve the technical effects of the present invention, and should also be considered as falling within the scope of the present invention.
Claims (10)
1. A self-aligned polysilicon and monocrystalline silicon hybrid MEMS vertical electrode is characterized in that: the polycrystalline silicon fixed electrode is fixed on the monocrystalline silicon fixed column through a silicon dioxide layer and is electrically connected with the monocrystalline silicon fixed column through a contact hole; the monocrystalline silicon fixing column is bonded on the monocrystalline silicon substrate, and an insulating layer is arranged between the monocrystalline silicon fixing column and the monocrystalline silicon substrate; the monocrystalline silicon movable electrode is connected with the MEMS functional structure; the horizontal distance W is formed between the monocrystalline silicon movable electrode and the polycrystalline silicon fixed electrode, the bottom of the monocrystalline silicon movable electrode is lower than that of the polycrystalline silicon movable electrode, and the height difference is D 1 The top of the polysilicon fixed electrode is higher than the monocrystalline silicon movable electrode, and the height difference is D 2 (ii) a A cavity is arranged between the monocrystalline silicon movable electrode, the polycrystalline silicon fixed electrode and the monocrystalline silicon substrate to provide space for the free movement of the monocrystalline silicon movable electrode。
2. The self-aligned polycrystalline silicon single crystal silicon hybrid MEMS vertical electrode of claim 1, wherein: the MEMS functional structure is a reflector, a mass block or a vibrator.
3. The self-aligned polysilicon-single crystal silicon hybrid MEMS vertical electrode of claim 1 or 2, wherein: silicon dioxide is left between the polysilicon fixed electrode and the monocrystalline silicon fixed column.
4. A method for manufacturing a self-aligned polysilicon-monocrystalline silicon hybrid MEMS vertical electrode is characterized by comprising the following steps:
(1) Etching monocrystalline silicon on the surface of the monocrystalline silicon wafer through a photoresist mask to form a first cavity, an edge bonding area and a fixed bonding column;
(2) Etching through a photoresist mask in the first cavity to form a deep groove, dividing a monocrystalline silicon wafer into a monocrystalline silicon movable electrode column, a monocrystalline silicon fixed column and an edge region in the horizontal direction by the deep groove, etching on the monocrystalline silicon fixed column to form a first cavity step and a fixed bonding column, and etching the edge region to form an edge step; is divided into a substrate layer and a MEMS structural layer in the vertical direction;
(3) Oxidizing the monocrystalline silicon wafer treated in the step (2) to generate a silicon dioxide layer, and then etching the silicon dioxide layer on the first concave cavity step through a photoresist mask to form a contact hole;
(4) Depositing a polycrystalline silicon layer on the surface of the monocrystalline silicon wafer treated in the step (3) by an in-situ doping CVD method and annealing;
(5) Etching the polysilicon layer without mask, removing a part of the polysilicon layer to form a polysilicon second surface, exposing the monocrystalline silicon fixing column and the silicon dioxide layer first surface of the marginal region, wherein the polysilicon second surface is lower than the silicon dioxide layer first surface;
(6) Covering the monocrystalline silicon fixing column with a photoresist mask, etching the polycrystalline silicon layer, wherein the polycrystalline silicon protected by the photoresist mask is not etched to form a polycrystalline silicon fixing region, the polycrystalline silicon on the edge step is etched to expose silicon dioxide, part of the polycrystalline silicon in the deep groove is etched to form a polycrystalline silicon third surface, the polycrystalline silicon third surface is lower than the first surface of the monocrystalline silicon movable electrode column, and the residual polycrystalline silicon in the deep groove forms a fixed electrode of the MEMS structure layer;
(7) Corroding the silicon dioxide layer on the surface of the monocrystalline silicon wafer processed in the step (6) to expose the first surface of the monocrystalline silicon movable electrode column and the first surface of the edge bonding area; then removing the photoresist mask, corroding and removing the silicon dioxide layer on the surface of the fixed bonding column to expose the first surface of the fixed bonding column to form a structural wafer;
(8) Bonding the structural wafer obtained in the step (7) to a base plate wafer to form a bonded wafer, wherein the base plate wafer consists of a monocrystalline silicon substrate and an insulating layer;
(9) Removing the substrate layer, exposing the silicon dioxide layer on the back of the deep groove, covering the monocrystalline silicon fixing column and the edge bonding region of the bonding wafer by using a photoresist mask, etching monocrystalline silicon, etching the monocrystalline silicon movable electrode column to form a second surface of the monocrystalline silicon movable electrode column, wherein the second surface of the monocrystalline silicon movable electrode column is lower than the second surface of the silicon dioxide layer on the back of the deep groove;
(10) And removing the photoresist on the bonding wafer, corroding the silicon dioxide layer between the polycrystalline silicon layer and the monocrystalline silicon movable electrode column, releasing the monocrystalline silicon movable electrode column to form a monocrystalline silicon movable electrode, and forming a polycrystalline silicon fixed electrode by the polycrystalline silicon in the deep groove.
5. The method of manufacturing a self-aligned polysilicon single crystal silicon hybrid MEMS vertical electrode of claim 4, wherein: in the step (3), the monocrystalline silicon wafer can be thermally oxidized firstly, a thin silicon dioxide layer is formed on all the surfaces, and after the thin silicon dioxide layer is corroded, the monocrystalline silicon wafer is thermally oxidized again to form the silicon dioxide layer.
6. The method of manufacturing a self-aligned polysilicon single crystal silicon hybrid MEMS vertical electrode of claim 4, wherein: the step (5) can also be: firstly thinning the polysilicon layer until the first concave cavity step is just exposed, then forming a contact hole, then depositing the polysilicon layer for the second time and annealing, and finally thinning the polysilicon layer deposited for the second time.
7. The method of manufacturing a self-aligned polysilicon-single crystal silicon hybrid MEMS vertical electrode of claim 4, wherein: and (4) in the step (7), the corrosion amount of silicon dioxide between the monocrystalline silicon movable electrode column and the polycrystalline silicon fixed area is larger than that of silicon dioxide between the polycrystalline silicon fixed area and the monocrystalline silicon fixed column.
8. The method of manufacturing a self-aligned polysilicon single crystal silicon hybrid MEMS vertical electrode of claim 4, wherein: and (5) silicon dioxide is remained between the polycrystalline silicon fixed electrode and the monocrystalline silicon fixed column in the step (10).
9. The method of manufacturing a self-aligned polysilicon single crystal silicon hybrid MEMS vertical electrode of claim 4, wherein: the horizontal spacing between the movable electrode of single crystal silicon and the fixed electrode of polycrystalline silicon is determined by the thickness of the silicon dioxide layer formed in step (3).
10. The method of manufacturing a self-aligned polysilicon single crystal silicon hybrid MEMS vertical electrode of claim 5, wherein: the horizontal distance between the movable single-crystal silicon electrode and the fixed polycrystalline silicon electrode is determined by the thickness of a silicon dioxide layer formed by thermally oxidizing a single-crystal silicon wafer.
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