CN113292040B

CN113292040B - MEMS filter and preparation method

Info

Publication number: CN113292040B
Application number: CN202110600933.4A
Authority: CN
Inventors: 周华芳
Original assignee: Chengdu Hiwafer Technology Co Ltd
Current assignee: Chengdu Hiwafer Technology Co Ltd
Priority date: 2021-05-31
Filing date: 2021-05-31
Publication date: 2023-05-19
Anticipated expiration: 2041-05-31
Also published as: CN113292040A

Abstract

The invention discloses a MEMS filter and a preparation method thereof, wherein the filter comprises: a substrate; a first reflective layer over the substrate; a sacrificial layer on the first reflective layer, the sacrificial layer having a cavity; the second reflection layer is positioned on the sacrificial layer, a floating bridge area with a release hole is arranged at the position of the second reflection layer corresponding to the cavity, and an annular anti-cracking beam penetrating through the second reflection layer is arranged in the floating bridge area; one of the upper surface and the lower surface of the anti-cracking beam is concave, and the other surface is convex. The anti-cracking beam is internally provided with a working plane, the parallelism is good, the anti-cracking beam region is similar to a series of micro springs, the toughness of the whole floating bridge region can be enhanced, and the floating bridges on the two sides of the anti-cracking beam are connected, so that the connection is firmer, the floating bridge region is not easy to crack, namely the floating bridge region cannot be caused to float up and down due to the driving of electrostatic force.

Description

MEMS filter and preparation method

Technical Field

The invention relates to a MEMS filter and a preparation method thereof.

Background

MEMS technology was known as a revolutionary high-tech technology in the 21 st century, and its development began in the 60 th year of the 20 th century, MEMS being an abbreviation for english Micro Electro Mechanical System, i.e. a microelectromechanical system. Microelectromechanical Systems (MEMS) are a new multidisciplinary technology developed in recent years that will revolutionize future human life. The basic technologies of MEMS mainly include silicon anisotropic etching technology, silicon bonding technology, surface micromachining technology, LIGA technology, etc., which have become essential core technologies for developing and producing MEMS.

The MEMS filter generally includes an upper POLY layer (reflective layer), a sacrificial layer, and a lower POLY layer on a substrate, and needs to be perforated to remove a part of the sacrificial layer to form a hollow structure, that is, a cantilever (floating bridge) is formed on the POLY layer above the hollow structure in the process of the preparation process, and an intermediate sacrificial layer connects the upper multi-layer film and the lower multi-layer film together; after the sacrificial layer is etched away, in the actual use process, the floating bridge can change in position under the action of electrostatic force, and the floating bridge is easy to break.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides an MEMS filter and a preparation method thereof.

The aim of the invention is realized by the following technical scheme:

in a first aspect of the present invention, there is provided a MEMS filter comprising:

a substrate;

a first reflective layer over the substrate;

a sacrificial layer on the first reflective layer, the sacrificial layer having a cavity;

the second reflection layer is positioned on the sacrificial layer, a floating bridge area with a release hole is arranged at the position of the second reflection layer corresponding to the cavity, and an annular anti-cracking beam penetrating through the second reflection layer is arranged in the floating bridge area;

one of the upper surface and the lower surface of the anti-cracking beam is concave, and the other surface is convex.

Further, an isolation layer is also arranged between the substrate and the first reflecting layer.

Further, the first reflecting layer is a first DBR dielectric film, and the second reflecting layer is a second DBR dielectric film; the first DBR dielectric film and the second DBR dielectric film comprise polycrystalline silicon layers and silicon nitride layers which are alternately arranged; the rupture prevention beam is located in each layer of the second DBR dielectric film and comprises a concave surface and a convex surface.

Further, the annular anti-cracking beam is a plurality of concentric rings.

In a second aspect of the present invention, there is provided a method for manufacturing a MEMS filter, comprising:

sequentially growing a first reflecting layer and a sacrificial layer on a substrate, wherein an annular first concave part or an annular first convex part is arranged on the upper part of the sacrificial layer;

a second reflecting layer is grown on the upper part of the sacrificial layer, concave-convex and concave-convex parts are formed on the second reflecting layer corresponding to the first concave parts, or concave-convex and concave-convex parts are formed on the second reflecting layer corresponding to the first convex parts, and the concave-convex parts are used as anti-cracking beams;

forming a release hole around the rupture preventing beam on the second reflective layer;

and forming a cavity in the sacrificial layer through the release hole, and forming a floating bridge region by a second reflecting layer corresponding to the cavity.

Further, the forming a cavity in the sacrificial layer through the release hole includes:

soaking the device in BOE solution, and removing part of the sacrificial layer by wet etching to form a cavity;

and (5) after taking out, washing the excessive BOE solution by using deionized water.

Further, after the second reflective layer is grown on the upper portion of the sacrificial layer and before the step of forming the release hole, the method further includes: the manufacturing of the upper electrode and the lower electrode specifically comprises the following steps:

digging holes on the second reflecting layer to form upper electrode holes, and digging holes on the second reflecting layer and the sacrificial layer to form lower electrode holes;

upper and lower electrodes are formed in the upper and lower electrode holes.

Further, forming a release hole around the rupture prevention beam on the second reflective layer, specifically includes:

forming a protective metal layer on the second reflecting layer which is manufactured by the upper electrode and the lower electrode;

forming a photoresist layer on the protective metal layer;

sequentially forming holes on the photoresist layer, the protective metal layer and the second reflecting layer to form release holes;

removing the photoresist layer;

after the cavity is formed in the sacrificial layer through the release hole, the method further comprises:

and removing the protective metal layer.

Further, the annular anti-cracking beam is a plurality of concentric rings.

The beneficial effects of the invention are as follows:

(1) In an exemplary embodiment of the present invention, during the actual operation of the filter with the anti-cracking beam, the inside of the anti-cracking beam is a working plane, the parallelism is good, the anti-cracking beam region is similar to a series of annularly distributed micro springs (similar to trampoline), the toughness of the whole floating bridge region can be enhanced, the floating bridges on two sides of the anti-cracking beam are connected, so that the connection is firmer, the floating bridge region is not easy to crack, i.e. the floating bridge region cannot float up and down due to the driving of electrostatic force, so that the floating bridge region is not cracked.

(2) In an exemplary embodiment of the present invention, when the upper surface of the anti-cracking beam is concave, and the lower surface of the anti-cracking beam is convex, the contact between the first reflective layer and the second reflective layer can be changed from surface contact to point contact, and the floating bridge area of the second reflective layer is not easy to adhere to the first reflective layer due to electrostatic adsorption by the point contact, so that the cracking risk of the floating bridge area can be further reduced.

(3) In an exemplary embodiment of the present invention, both the first reflective layer and the second reflective layer are realized in multiple layers, so that not only can the anti-reflection effect on the light wavelength be better, but also the anti-cracking effect of the anti-cracking beam can be further improved, because each layer comprises a concave surface and a convex surface of the anti-cracking spring structure.

(4) In an exemplary embodiment of the invention, the metal electrode and the second reflecting layer are prevented from being damaged by wet etching in the cavity manufacturing step, so that the metal protecting layer is used for protecting the metal electrode and the second reflecting layer before manufacturing, the metal protecting layer is etched into the cavity, the second reflecting layer is kept complete, the developed product meets the process requirements, the operation is simple, the metal protecting layer is compatible with the semiconductor manufacturing process, and the product development efficiency and success rate are improved.

Drawings

FIG. 1 is a schematic diagram of a MEMS filter according to an exemplary embodiment of the present invention;

FIG. 2 is a schematic diagram of a MEMS filter according to yet another exemplary embodiment of the present invention;

FIG. 3 is a schematic diagram of a MEMS filter with isolation layers according to an exemplary embodiment of the present invention;

FIG. 4 is a schematic view of a MEMS filter with a multilayer film structure according to an exemplary embodiment of the present invention;

FIG. 5 is a schematic illustration of the construction of a rupture beam according to an exemplary embodiment of the present invention;

FIG. 6 is a schematic view of a rupture beam according to yet another exemplary embodiment of the present invention;

FIG. 7 is a flow chart of a method of fabricating a MEMS filter in accordance with an exemplary embodiment of the present invention;

fig. 8 is a schematic structural diagram of step S1 of a method for manufacturing a MEMS filter according to an exemplary embodiment of the present invention;

fig. 9 is a schematic diagram of a recess structure of step S1 of a method for manufacturing a MEMS filter according to an exemplary embodiment of the present invention;

fig. 10 is a schematic diagram showing a convex structure of step S1 of a method for manufacturing a MEMS filter according to an exemplary embodiment of the present invention;

fig. 11 is a schematic structural diagram of step S3 of a method for manufacturing a MEMS filter according to an exemplary embodiment of the present invention;

fig. 12 is a schematic structural diagram of step S5 of a method for manufacturing a MEMS filter according to an exemplary embodiment of the present invention;

fig. 13 is a schematic structural diagram of step S7 of a method for manufacturing a MEMS filter according to an exemplary embodiment of the present invention;

fig. 14 is a schematic structural diagram of step S61 of a method for manufacturing a MEMS filter according to an exemplary embodiment of the present invention;

fig. 15 is a schematic structural diagram of step S62 of a method for manufacturing a MEMS filter according to an exemplary embodiment of the present invention;

fig. 16 is a schematic structural diagram of step S51 of a method for manufacturing a MEMS filter according to an exemplary embodiment of the present invention;

in the figure, 1-substrate, 2-first reflective layer, 3-sacrificial layer, 31-cavity, 32-first recess, 33-first protrusion, 4-second reflective layer, 41-floating bridge region, 411-release hole, 412-anti-cracking beam, 4121-convex, 4122-concave, 42-upper electrode hole, 43-lower motor hole, 5-isolation layer, 6-polysilicon layer, 7-silicon nitride layer, 8-upper electrode, 9-lower electrode, 10-protection metal layer.

Detailed Description

The following description of the embodiments of the present invention will be made apparent and fully understood from the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the description of the present invention, it should be noted that directions or positional relationships indicated as being "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are directions or positional relationships described based on the drawings are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements to be referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.

In addition, the technical features of the different embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.

Referring to fig. 1 and 2, fig. 1 and 2 illustrate a MEMS filter provided in two exemplary embodiments of the present invention, comprising:

a substrate 1;

a first reflective layer 2 over the substrate 1;

a sacrificial layer 3 on the first reflective layer 2, the sacrificial layer 3 having a cavity 31;

the second reflection layer 4 is located on the sacrificial layer 3, the position of the second reflection layer 4 corresponding to the cavity 31 is a floating bridge area 41 with a release hole 411, and an annular anti-cracking beam 412 penetrating through the second reflection layer 4 is further arranged in the floating bridge area 41;

one of the upper and lower surfaces of the rupture prevention beam 412 is a concave surface 4122, and the other surface is a convex surface 4121.

Specifically, in this exemplary embodiment as shown in FIG. 1, the burst beam 412 has a concave surface 4122 on the upper side (away from the substrate 1) and a convex surface 4121 on the lower side (toward the substrate 1); whereas in the exemplary embodiment shown in fig. 2, the burst beam 412 is convex 4121 on the upper side (away from the substrate 1) and concave 4122 on the lower side (toward the substrate 1).

When the structure of this exemplary embodiment is adopted, in the actual working process of the filter, the inside of the anti-cracking beam 412 is a working plane, the parallelism is good, the anti-cracking beam 412 is similar to a series of annularly distributed micro springs (similar to trampoline), the toughness of the whole floating bridge area 41 can be enhanced, the floating bridges on two sides of the anti-cracking beam 412 are connected, so that the connection is firmer, the floating bridge area 41 is not easy to crack, that is, the floating bridge area 41 cannot float up and down due to the driving of electrostatic force, so that the floating bridge area 41 is not cracked.

In addition, when the embodiment in which the upper surface (away from the substrate 1) of the anti-cracking beam 412 is concave 4122 and the lower surface (close to the substrate 1) is convex 4121 as shown in fig. 1 is adopted, the contact between the first reflective layer 2 and the second reflective layer 4 can be changed from the surface contact to the point contact, and the floating bridge region 41 of the second reflective layer 4 is not easily adhered to the first reflective layer 2 due to electrostatic adsorption by the point contact, so that the risk of cracking of the floating bridge region 41 can be further reduced.

More preferably, in an exemplary embodiment, as shown in fig. 3, a spacer layer 5 is further disposed between the substrate 1 and the first reflective layer 2.

In this exemplary embodiment, the material of the isolation layer 5 is silicon dioxide.

More preferably, in an exemplary embodiment, as shown in fig. 4, the first reflective layer 2 is a first DBR dielectric film, and the second reflective layer 4 is a second DBR dielectric film; the first DBR dielectric film and the second DBR dielectric film comprise polycrystalline silicon layers 6 and silicon nitride layers 7 which are alternately arranged; the rupture prevention beam 412 is located in each layer of the second DBR dielectric film and includes a concave surface 4122 and a convex surface 4121.

Specifically, in the exemplary embodiment shown in fig. 4, the first DBR dielectric film includes seven layers, namely, a polysilicon layer 6, a silicon nitride layer 7, and a polysilicon layer 6 in order from the direction from the substrate 1 to the direction away from the substrate 1; the second DBR dielectric film comprises six layers, namely a polysilicon layer 6, a silicon nitride layer 7, a polysilicon layer 6 and a silicon nitride layer 7 in sequence from the direction close to the substrate 1 to the direction far away from the substrate 1.

Compared to the single Poly layer of the prior art, the first reflective layer 2 and the second reflective layer 4 of the present application are realized by multiple layers, and the anti-reflection effect of the multi-layer film structure on the light wavelength is more, and the anti-cracking effect of the anti-cracking beam 412 can be further improved, because each layer comprises the anti-cracking spring structure of the concave surface 4122 and the convex surface 4121.

More preferably, in an exemplary embodiment, the annular rupture prevention beam 412 is a plurality of concentric rings.

In particular, this way it is possible to have the effect that the entire pontoon area 41 has a reduced risk of rupture of the pontoon area 41. Wherein fig. 5 and 6 respectively show two exemplary embodiments thereof: as shown in fig. 5, the top view of the floating bridge region 41 formed by the release holes 411 is circular, and the rupture preventing beams 412 are concentric circles separating the floating bridge region 41 into an inner ring and an outer ring, so that the entire floating bridge region 41 can be subjected to the rupture preventing beams 412. As shown in fig. 6, the floating bridge region 41 formed by the relief holes 411 has a circular shape in plan view, and the rupture prevention beams 412 have a plurality of concentric square rings.

In addition, based on the implementation of any of the above exemplary embodiments, the material of the sacrificial layer 3 is silicon dioxide.

Referring to fig. 7, fig. 7 shows a flowchart of a method for manufacturing a MEMS filter according to still another exemplary embodiment of the present invention, including:

s1: as shown in fig. 8, a first reflective layer 2 and a sacrificial layer 3 are sequentially grown on a substrate 1; the sacrificial layer 3 is provided with an annular first concave portion 32 or an annular first convex portion 33 at an upper portion thereof as shown in fig. 9 and 10, respectively.

Wherein the first concave portion 32 or the first convex portion 33 is used for manufacturing the rupture prevention beam 412 later. The substrate 1 adopts a double polished silicon wafer, and the thickness of the wafer is 400 microns; after the wafer is cleaned, the growth of the first reflecting layer 2 can be carried out by an LPCVD machine, and the thickness of the film layer is manufactured according to the design requirement; the preparation of the sacrificial layer 3 can be carried out in a PECVD mode, the thickness of the film layer is manufactured according to the design requirement, and the silicon dioxide of the sacrificial layer 3 is prepared in a PECVD mode, so that the etching selectivity between the sacrificial layer 3 and the reflecting layer in the subsequent etching process of the floating bridge region 41 of the sacrificial layer 3 can be improved, and the manufacturing of the subsequent floating bridge region 41 is facilitated.

When the first recess 32 is formed, etching may be performed on the sacrificial layer 3 by dry etching; when the first convex portion 33 is formed, a part of the sacrificial layer 3 may be grown more in a partially grown manner (any other realizable manner may be used, and the method is not limited thereto).

In the subsequent process of growing the second reflective layer 4, the upper multilayer film forms a groove or a bump at the position of the first concave portion 32 or the first convex portion 33, and the subsequent sacrificial layer 3 is etched to form a floating bridge region 42 at the corresponding position of the second reflective layer 4.

S3: a second reflection layer 4 is grown on the sacrificial layer 3, and concave-convex portions (vertical direction) are formed at positions corresponding to the first concave portions 32 on the second reflection layer 4 or concave-convex portions are formed at positions corresponding to the first convex portions 33 on the second reflection layer 4, and the concave-convex portions serve as rupture prevention beams 412, as shown in fig. 11 (the same is true only for the case where concave-convex portions are formed at positions corresponding to the first concave portions 32 on the second reflection layer 4).

Specifically, in this step, the growth may be performed using an LPCVD tool.

S5: a release hole 411 is formed around the rupture prevention beam 412 on the second reflection layer 4 as shown in fig. 12.

Wherein the release holes 411 are between about 1.5 and 3 microns in size and the hole-to-hole spacing is between about 10 and 30 microns; the etching solution is not easy to enter after the holes are too small, and the second reflecting layer 4 is not firm enough and is easy to damage after the holes are too large and are manufactured later; the hole spacing is too large, the sacrificial layer 3 is not easy to dig, the hole spacing is too small, the small holes are too dense, and the second reflecting layer 4 is easy to damage after being manufactured.

The release holes 411 are formed in the form of dry etching. It should be noted that, the dry etching needs to reach a part of the sacrificial layer 3, the etching time can be properly adjusted according to the thickness of the sacrificial layer 3, the depth of the sacrificial layer 3 is deep, then the subsequent cavity 31 is made by wet etching, the side wall of the cavity 31 has a slope, the depth of the sacrificial layer 3 is shallow, and the side wall of the cavity 31 is straight in angle during the subsequent etching, but at least the sacrificial layer is needed to be 500-1000 angstroms.

S7: a cavity 31 is formed in the sacrificial layer 3 through the release hole 411, and a floating bridge region 41 is formed in the second reflective layer 4 corresponding to the cavity 31, as shown in fig. 13.

In yet another specific exemplary embodiment, the forming of the cavity 31 in the sacrificial layer 3 through the release hole 411 in step S7 includes:

s71: immersing the device in a BOE solution, and removing part of the sacrificial layer 3 by wet etching to form a cavity 31;

s72: and (5) after taking out, washing the excessive BOE solution by using deionized water.

BOE solution concentration is 1% -10% for about 3-4 hours. In this process, the second reflective layer 4 of the device is easily broken, and wet etching is performed in a still mild manner during etching, so that cleaning actions such as bubbling and shaking are strictly prohibited.

More preferably, in an exemplary embodiment, after the second reflective layer 4 is grown on the sacrificial layer 3, and before the step of forming the release hole 411, the method further includes: s6: the upper electrode 8 and the lower electrode 9 are manufactured, and specifically include:

s61: as shown in fig. 14, an upper electrode hole 42 is bored in the second reflection layer 4, and a lower electrode hole 43 is bored in the second reflection layer 4 and the sacrifice layer 3;

s62: as shown in fig. 15, the upper electrode 8 and the lower electrode 9 are formed in the upper electrode hole 42 and the lower electrode hole 43.

Specifically, in this exemplary embodiment, the fabrication of the MEMS filter requires the upper electrode 8 and the lower electrode 9, and thus the preparation is selected between the steps S5 and S7. Wherein the material of the upper electrode 8 and the lower electrode 9 is Al.

More preferably, in an exemplary embodiment, the release hole 411 is formed around the rupture preventing beam 412 on the second reflecting layer 4, and specifically includes:

s51: as shown in fig. 16, a protective metal layer 10 is formed on the second reflecting layer 4 where the fabrication of the upper electrode 8 and the lower electrode 9 is completed;

s52: forming a photoresist layer on the protective metal layer 10;

s53: sequentially forming a photoresist layer, a protective metal layer 10 and a second reflecting layer 4 to form a release hole 411;

s54: removing the photoresist layer;

s8: and removing the protective metal layer.

Specifically, since the scheme of step S7, i.e. "forming the cavity 31 in the sacrificial layer 3 through the release hole 411", is preferably implemented by wet etching (BOE solution), the metal electrodes (the upper electrode 8 and the lower electrode 9) are easily etched by the BOE solution due to their strong chemical activity (for example, when Al is used); the second reflective layer 4 also has a risk of being etched by the BOE solution (especially in the case of the example embodiment described later, the uppermost layer is a silicon nitride film), so in this example embodiment, protection needs to be provided for the electrode and the second reflective layer 4, otherwise damage to the electrode and the second reflective layer 4 is easily caused during the process of manufacturing the cavity 31, and the performance of the product is affected.

In step S51, the protective metal layer 10 is preferably a gold layer, after the wafer is cleaned, a layer of pure gold is sputtered on the front surface of the wafer by using a magnetron sputtering machine, the gold layer is manufactured by adopting a sputtering method, and the side edge of the wafer can also be sputtered with metal, so that the wafer side edge protection effect is achieved.

For step S52, when the etching hole photoresist layer is manufactured, the thickness of the photoresist and the etching selection ratio of the subsequent dry etching multilayer film need to be considered, the residual photoresist is ensured after the subsequent dry etching enters the sacrificial layer 3, and if the residual photoresist is not available, the electrode and the second reflecting layer 4 below the photoresist are etched after the photoresist is etched; if the photoresist layer is too thick, the development of the etching holes is easily problematic, and the photoresist at the bottom of the etching holes cannot be completely developed, which affects the subsequent etching of the release holes 411.

For step S53, the gold layer at the release hole 411 is not removed before etching by several methods, and the gold layer needs to be etched by dry method in the dry etching process, the etching rate of the gold layer by dry method is low, the etching time is long, the photoresist is easy to be insufficient in step S52, and the gold particles on the wafer surface are easy to remain by dry etching, if the etching hole is blocked, the subsequent cavity formation of the sacrificial layer is affected, so the gold layer at the position of the etching hole needs to be removed first. In an exemplary embodiment, a diluted potassium iodide solution (1% -10% strength) is used to remove the gold layer at the location of the etch holes, the time being dependent on the gold layer thickness. Examples: a gold layer of 2000 a thickness is immersed in a dilute potassium iodide solution for about 7-8 seconds, the gold layer at the etched holes is etched clean, and the gold layer at the photoresist covered locations is not etched.

The second reflecting layer 4 is provided with an opening in step S53 by dry etching, an ICP etching machine is used, and the etching gas is CF ₄ &O ₂ The gas flow is 0-2000sccm, the RF power of the upper electrode is 100-600W, the RF power of the lower electrode is 0-200W, and the process pressure is 10mtorr-1.5Par. The etching time can be properly adjusted according to the thickness of the entering sacrificial layer 3, the depth of the entering sacrificial layer 3 is deep, the cavity side wall has a gradient when the subsequent wet etching is performed, the depth of the entering sacrificial layer 3 is shallow, the cavity side wall angle is straight when the subsequent etching is performed, but at least 500-1000 angstroms of the entering sacrificial layer is needed.

And (3) for removing the photoresist layer in the step S54, adopting an 80 ℃ NMP solution flushing process, wherein the flushing pressure is 300-1500Psi, and the flushing time is about 3-10min. Excess NMP solution is rinsed with IPA solution and finally wafer is dried by a dryer, oven or nitrogen gun. Finally adopt O ₂ The ashing process removes photoresist residues on the wafer surface to prevent photoresist residues in the etched holes.

For the step S8 of removing the protective metal layer 10 (i.e. gold layer) at the position of the release hole 411, after the deionized water washes out the redundant BOE solution, dilute potassium iodide solution (with concentration of 1% -10%) is added to remove the protective gold layer of the wafer, and the time is determined according to the thickness of the gold layer. After the gold layer is removed, the gold layer is put into deionized water solution for cleaning, and redundant potassium iodide solution is cleaned. And finally, adopting hot nitrogen to dry. The hot nitrogen drying temperature is not too high, the blow-drying air pressure is not too high, and the hot nitrogen drying temperature is 50-80 ℃ for about 5-10min.

Correspondingly, in the growth phase of step S1, the substrate 1 is front-side grown with a first DBR dielectric film: the substrate 1 adopts a double polished silicon wafer, and the thickness of the wafer is 400 microns; after the wafer is cleaned, adopting an LPCVD machine to grow SiO in sequence ₂ The (sacrificial layer)/polysilicon layer 6/silicon nitride layer 7/polysilicon layer 6, the thickness of the film layer is made according to the design requirement, the polysilicon layer 6 on the uppermost layer of the front surface of the first DBR dielectric film is heavily doped with B or P by an ion implantation machine after being grown, the doping concentration is made according to the design requirement, and then the rapid annealing process is used for annealing to improve the conductivity of the doped layer.

In the growth phase of step S3, for growing the second DBR dielectric film: after cleaning, a LAPECVD machine is adopted to grow a polysilicon layer 6 on the front surface, ion implantation heavy doping B or P is carried out on the polysilicon layer 6, the doping concentration is carried out according to design requirements, RTA rapid annealing is carried out on a wafer, and then LPCVD is adopted to manufacture second DBR dielectric films of the silicon nitride layer 7, the polysilicon layer 6, the silicon nitride layer 7, the polysilicon layer 6 and the silicon nitride layer 7 on the front and back surfaces of the wafer.

In the electrode manufacturing process, the heavily doped polysilicon layer 6 of the second DBR dielectric film is used as the conductive layer of the upper electrode 8, and the heavily doped polysilicon layer 6 of the first DBR dielectric film is used as the conductive layer of the lower electrode 9.

The concentric rings make the spring structure more firm.

It is apparent that the above examples are given by way of illustration only and not by way of limitation, and that other variations or modifications may be made in the various forms based on the above description by those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present invention.

Claims

1. A MEMS filter, characterized by: comprising the following steps:

a substrate;

a first reflective layer over the substrate;

the second reflection layer is positioned on the sacrificial layer, a floating bridge area with a release hole is arranged at the position of the second reflection layer corresponding to the cavity, and an annular anti-cracking beam penetrating through the second reflection layer is arranged in the floating bridge area; digging holes on the second reflecting layer to form upper electrode holes, and digging holes on the second reflecting layer and the sacrificial layer to form lower electrode holes; forming upper and lower electrodes in the upper and lower electrode holes;

one of the upper surface and the lower surface of the anti-cracking beam is concave, and the other surface is convex;

the first reflecting layer is a first DBR dielectric film, and the second reflecting layer is a second DBR dielectric film; the first DBR dielectric film and the second DBR dielectric film comprise polycrystalline silicon layers and silicon nitride layers which are alternately arranged; each layer of the rupture prevention beam positioned on the second DBR dielectric film comprises a concave surface and a convex surface; or: the annular anti-cracking beam is a plurality of concentric rings.

2. A MEMS filter as claimed in claim 1, wherein: an isolation layer is also provided between the substrate and the first reflective layer.

3. A preparation method of an MEMS filter is characterized in that: comprising the following steps:

forming a cavity in the sacrificial layer through the release hole, and forming a floating bridge area by a second reflecting layer corresponding to the cavity;

after the second reflective layer is grown on the sacrificial layer, and before the step of forming the release hole, the method further includes: the manufacturing of the upper electrode and the lower electrode specifically comprises the following steps:

forming upper and lower electrodes in the upper and lower electrode holes;

the first reflecting layer is a first DBR dielectric film, and the second reflecting layer is a second DBR dielectric film; the first DBR dielectric film and the second DBR dielectric film comprise polycrystalline silicon layers and silicon nitride layers which are alternately arranged; each layer of the rupture prevention beam positioned on the second DBR dielectric film comprises a concave surface and a convex surface; or the annular anti-cracking beam is a plurality of concentric rings.

4. A method of manufacturing a MEMS filter according to claim 3, wherein: the forming of the cavity in the sacrificial layer through the release hole includes:

5. A method of manufacturing a MEMS filter according to claim 3, wherein: forming release holes around the rupture prevention beam on the second reflective layer, specifically including:

forming a photoresist layer on the protective metal layer;

removing the photoresist layer;

and removing the protective metal layer.