F-P cavity filter based on piezoelectric effect and preparation method thereof

Abstract

The invention relates to the technical field of filtering, in particular to an F-P cavity filter based on a piezoelectric effect and a preparation method of the F-P cavity filter. An upper polar plate; the first reflecting layer and the second reflecting layer are arranged in the supporting frame, are parallel to each other all the time and are used for jointly limiting a Fabry-Perot resonant cavity; the driving assembly is connected between the upper polar plate and the supporting frame, and a driving unit is arranged in the driving assembly; the driving unit is formed by combining a telescopic layer and at least one non-piezoelectric layer, and the telescopic layer comprises a piezoelectric layer, a bottom electrode located at the bottom of the piezoelectric layer and a top electrode located at the top of the piezoelectric layer; the at least one non-piezoelectric layer is configured to be attached to the bottom electrode and / or the top electrode. The piezoelectric driving structure can realize miniaturization of the filter, the structure is simplified, the overall size and weight are reduced, and the device reliability is high.

Description

Technical Field

[0001] The present application relates to the field of filtering technology, and in particular to a FP cavity filter based on piezoelectric effect and a preparation method of the FP cavity filter based on piezoelectric effect. Background Art

[0002] MEMS (Micro-Electro-Mechanical System) driving technology is the technical guarantee for realizing the adjustable filtering function of MEMS-based FP (Fabry Pérot) cavity filter chip. The MEMS-based FP cavity filter uses the principle of micro-nanostructure to control optical parameters such as interference, diffraction and dispersion to achieve filtering effect. The filtering performance can be customized by changing the size, shape and material of the micro-nanostructure. The filter has the advantages of strong customization of filtering performance, simple structure and high spatial resolution, and has shown significant advantages in spectral detection. How to further simplify and miniaturize the structure of the FP filter, make the optical wavelength linearly adjustable over a wide range, and ensure high sensitivity to external forces and reliability has become a research hotspot. Summary of the invention

[0003] In view of the above situation, it is desirable to provide a FP cavity filter based on piezoelectric effect and a method for preparing the FP cavity filter based on piezoelectric effect.

[0004] According to one aspect of the present application, a FP cavity filter based on piezoelectric effect is provided, comprising a supporting frame; an upper electrode plate; a first reflective layer and a second reflective layer, both of which are arranged in the supporting frame and are always parallel to each other, so as to jointly define a Fabry-Perot resonant cavity; the first reflective layer is arranged on the upper electrode plate; a driving component connected between the upper electrode plate and the supporting frame, wherein a driving unit is arranged in the driving component; the driving unit is formed by a combination of a telescopic layer and at least one non-piezoelectric layer, wherein the telescopic layer comprises a piezoelectric layer, a bottom electrode located at the bottom of the piezoelectric layer, and a top electrode located at the top of the piezoelectric layer; the at least one non-piezoelectric layer is configured to be arranged in contact with the bottom electrode and / or the top electrode, so that after the electric field between the bottom electrode and the top electrode changes, the piezoelectric layer either stretches and drives the at least one non-piezoelectric layer to bend in the opposite direction of the side where the non-piezoelectric layer is located, or shortens and drives the at least one non-piezoelectric layer to bend in the direction where the non-piezoelectric layer is located, thereby driving the upper electrode plate to move away from or toward the second reflective layer to change the size of the Fabry-Perot resonant cavity.

[0005] In addition to or instead of one or more features described herein, a further embodiment of the FP cavity filter may include that the drive assembly includes at least two drive brackets, the at least two drive brackets are respectively connected between the support frame and the upper pole plate and are each provided with the drive unit, wherein there is at least a pair of the drive brackets respectively arranged on opposite sides of the upper pole plate.

[0006] In addition to or instead of one or more features described herein, a further embodiment of the FP cavity filter may include that the structures of the at least two drive brackets are consistent; and / or, the number of the drive brackets is four, and the four drive brackets are arranged in a centrally symmetrical manner relative to the geometric center of the upper plate.

[0007] In addition to or instead of one or more features described herein, a further embodiment of the FP cavity filter may include that each of the driving brackets includes at least one driving sub-bracket; the at least one driving sub-bracket is respectively connected between the supporting frame and the upper plate and is provided with the driving unit.

[0008] In addition to or instead of one or more features described herein, a further embodiment of the FP cavity filter may include that each of the driving sub-brackets includes a driving arm, a first connecting arm and a second connecting arm, and the driving unit is provided on the driving arm; the driving arm is connected to the upper pole plate through the first connecting arm, and is connected to the support frame through the second connecting arm.

[0009] In addition to or instead of one or more features described herein, a further embodiment of the FP cavity filter may include that the driving arm is provided with a first extension arm and a second extension arm, the first extension arm and the second extension arm each having a relative connecting end and a free end, the connecting end of the first extension arm and the connecting end of the second extension arm are connected to each other, the free end of the first extension arm is connected to the first connecting arm, and the free end of the second extension arm is connected to the second connecting arm; the first extension arm and the second extension arm are both configured as the driving unit and are capable of opening away from each other in opposite directions.

[0010] In addition to or as an alternative to one or more features described herein, further embodiments of the FP cavity filter may include that before being spread apart from each other, the first extension arm and the second extension arm extend in the same plane, and the opposite direction is perpendicular to the same plane; and / or, the first extension arm and the second extension arm of the driving arm are configured to be combined into a U-shape; and / or, the first connecting arm of the driving sub-bracket of the same driving bracket is connected to the middle of the connected edge of the upper electrode plate, and the second connecting arm is connected to the middle of the connected edge of the supporting frame; and / or, each of the second connecting arms is connected to the supporting frame through a planar electrode; and / or, the The first extension arm and the second extension arm are both formed by extending a telescopic layer and two non-piezoelectric layers in combination; the telescopic layers of the first extension arm and the second extension arm each have a first extension segment close to their respective connection ends and a second extension segment close to their respective free ends, the two non-piezoelectric layers of the first extension arm are respectively attached to the opposite sides of its telescopic layer, and respectively cover the first extension segment and the second extension segment of the telescopic layer; the two non-piezoelectric layers of the second extension arm are respectively attached to the opposite sides of its telescopic layer, and respectively cover the first extension segment and the second extension segment of the telescopic layer; the first extension segments of the telescopic layers of the first extension arm and the second extension arm are bent toward each other.

[0011] In addition to or as an alternative to one or more features described herein, further embodiments of the FP cavity filter may include that the telescopic layers of the first extension arm and the second extension arm both have a middle section covered by two non-piezoelectric layers at the same time.

[0012] In addition to or as an alternative to one or more features described herein, a further embodiment of the FP cavity filter may include that each of the driving brackets includes two driving sub-brackets, and the two driving sub-brackets are symmetrical structures with the center line of the upper plate as the symmetry axis.

[0013] According to another aspect of the present application, a method for preparing an FP cavity filter based on piezoelectric effect is provided, comprising: forming the non-piezoelectric layer, the bottom electrode, the piezoelectric layer, the top electrode and another non-piezoelectric layer layer by layer from bottom to top on the top surface of an SOI silicon wafer to constitute the driving unit; forming the first reflective layer on the top surface of the SOI silicon wafer; forming a cavity located below the first reflective layer on the bottom surface of the SOI silicon wafer; forming the second reflective layer on a base silicon wafer; bonding the SOI silicon wafer to the base silicon wafer to form the cavity into the Fabry-Perot resonant cavity defined by the first reflective layer and the second reflective layer; etching the top surface of the SOI silicon wafer to form the upper electrode plate provided with the first reflective layer, and suspending the upper electrode plate under the support of the driving component; the driving unit is provided in the driving component.

[0014] One of the above technical solutions has the following advantages or beneficial effects: In view of the shortcomings of the existing technology, the present application proposes a piezoelectric driven FP cavity filter in which the upper plate always moves parallel to the second reflective layer, which can keep the first reflective layer and the second reflective layer always parallel, and by setting a driving component including a driving unit, the movement range of the upper plate can be large, thereby improving the filtering efficiency and light utilization of the filter. At the same time, the driving unit is formed by a combination of a telescopic layer and at least one non-piezoelectric layer. The piezoelectric driving structure can realize the miniaturization of the entire filter, facilitate further simplification of the structure, reduce the overall volume and weight, improve the impact resistance and reliability of the device, and has great development potential in the future. The present application is the same as the conventional MEMS processing technology, and is compatible with the COMS (complementary metal oxide semiconductor) process.

[0015] Other advantages of the present application and the technical effects of the preferred embodiments will be further described in the following specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0017] Figure 1 is a three-dimensional schematic diagram of an FP cavity filter provided by at least one embodiment of the present application;

[0018] Figure 2 is a schematic plan view of a driving bracket provided in at least four embodiments of the present application;

[0019] Figure 3 yes Figure 2 (a) A schematic plan view of the driving bracket provided;

[0020] Figure 4 is a schematic top view of a driving arm provided by at least one embodiment of the present application;

[0021] Figure 5 is a cross-sectional schematic diagram of a second extension arm (before the driving arm is opened) provided in at least one embodiment of the present application;

[0022] Figure 6 is a front view schematic diagram of a driving arm (after being opened) provided by at least one embodiment of the present application;

[0023] Figure 7It is a process schematic diagram of a method for preparing a FP cavity filter provided in at least one embodiment of the present application.

[0024] Among them, the reference numerals in the figure are:

[0025] 1: Substrate silicon 2: Oxide buried layer

[0026] 3: Top silicon 4: Non-piezoelectric layer

[0027] 5: Bottom electrode 6: Piezoelectric layer

[0028] 7: Top electrode 8: Another non-piezoelectric layer

[0029] 9: First reflective layer 10: Base silicon wafer

[0030] 11: Second reflective layer 600: Telescopic layer

[0031] 60: Planar electrode 31: Upper electrode

[0032] 41: Driving sub-bracket 411: Driving arm

[0033] 412: first connecting arm 413: second connecting arm

[0034] 4111: first extension arm 4112: second extension arm

[0035] 1a: Connecting end 1b: Free end

[0036] 50: connected edge of the upper plate 80: connected edge of the support frame

[0037] 20: Second extension section 30: Middle section

[0038] 21: First extension section 500: FP cavity

[0039] 100: Centerline DETAILED DESCRIPTION

[0040] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0041] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0042] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0043] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0044] In addition, in the description of the present application, “plurality” means two or more than two, unless otherwise clearly and specifically defined.

[0045] by Figures 1 to 6 Taking the example of the present invention, a FP cavity filter based on the piezoelectric effect is described and introduced. The present invention provides a FP cavity filter, including a support frame, an upper electrode plate 31, a first reflective layer 9 and a second reflective layer 11, which are all arranged in the support frame and are always parallel to each other, so as to jointly define a Fabry-Perot resonant cavity 500; the first reflective layer 9 is arranged on the upper electrode plate 31; a driving component is connected between the upper electrode plate 31 and the support frame, and a driving unit is arranged in the driving component; the driving unit is formed by a combination of a telescopic layer 600 and at least one non-piezoelectric layer 4, and the telescopic layer includes a piezoelectric layer 6, a bottom electrode 5 located at the bottom of the piezoelectric layer 6 , and a top electrode 7 located on the top of the piezoelectric layer 6; at least one non-piezoelectric layer 4 is configured to be fitted on the bottom electrode 5 and / or the top electrode 7, so that after the electric field between the bottom electrode 5 and the top electrode 7 changes, the piezoelectric layer 6 either stretches and drives at least one non-piezoelectric layer 4 to bend in the opposite direction of the side where the non-piezoelectric layer 4 is located, or shortens and drives at least one non-piezoelectric layer 4 to bend in the direction of the side where the non-piezoelectric layer 4 is located, thereby driving the upper electrode plate to move away from or toward the second reflective layer to change the size of the Fabry-Perot resonant cavity 500.

[0046] It should be explained that the piezoelectric layer 6 can be understood as a piezoelectric material layer structure, and the non-piezoelectric layer 4 can be understood as a non-piezoelectric material layer structure. Piezoelectric material is a crystalline material that generates a voltage between the two end faces when subjected to pressure or tension. This material has a converse piezoelectric effect, that is, when an electric field is applied in the polarization direction of the dielectric, these dielectrics will deform, and when the electric field is removed, the deformation of the dielectric disappears. Non-piezoelectric materials do not have this converse piezoelectric effect, and the role of the non-piezoelectric layer 4 includes but is not limited to determining the direction of the bending deformation of the piezoelectric layer 6.

[0047] It should be noted that the non-piezoelectric material can be silicides such as silicon oxide and silicon nitride, and metal oxides such as aluminum oxide and titanium oxide. The bottom electrode 5 and the top electrode 7 can be made of metal conductive materials such as Mo, Ti, Pt, and Au, and the piezoelectric material can be a compound material such as AlN, PZT, ZnO, and LiNbO3.

[0048] Take a specific implementation as an example. Figure 5 As shown, the piezoelectric layer 6 at this time will shorten after the electric field between the bottom electrode 5 and the top electrode 7 changes, which can drive the non-piezoelectric layer 4 to change as shown in FIG. Figure 6 The second extension arm 4112 below is bent and deformed.

[0049] Of course, as long as the upper electrode plate 31 can be ensured to be always parallel to the second reflective layer 11 during translation, the arrangement and attachment of the non-piezoelectric layer 4 and the piezoelectric layer 6, as well as the elongation or shortening of the piezoelectric layer 6 under the action of the electric field are not specifically limited.

[0050] The present application proposes a piezoelectric driven FP cavity filter in which the upper electrode plate 31 always moves parallel to the second reflective layer 11. The filter can keep the first reflective layer 9 and the second reflective layer 11 always parallel to each other. Moreover, by setting a driving component including a driving unit, the upper electrode plate 31 can have a large movement range, thereby improving the filtering efficiency and light utilization of the filter. At the same time, the driving unit is formed by combining a telescopic layer 600 and at least one non-piezoelectric layer 4. The piezoelectric driving structure can realize the miniaturization of the entire filter, facilitate further simplification of the structure, reduce the overall volume and weight, improve the impact resistance and reliability of the device, and has great development potential in the future. The present application is the same as the conventional MEMS processing technology, and is compatible with the COMS (complementary metal oxide semiconductor) process.

[0051] It should be noted that the Bragg reflection layer can be a multi-layer material, mainly composed of high-refractive index materials such as TiO2, Ta2O5, Nb2O5 or SiN thin film, and low-refractive index materials such as SiO2, which are alternately composited.

[0052] In one embodiment of the present application, see Figure 1The driving component includes at least two driving brackets, at least two driving brackets are respectively connected between the supporting frame and the upper electrode plate 31 and are each provided with a driving unit, wherein there is at least a pair of driving brackets respectively arranged on opposite sides of the upper electrode plate 31; such an arrangement allows driving brackets to be arranged on opposite sides of the upper electrode plate 31, thereby ensuring the structural stability and high reliability of the upper electrode plate 31 during the translation process; of course, the driving component may also include a component that changes the electric field between the bottom electrode 5 and the top electrode 7, but since it is not the focus of this application, no specific explanation is given.

[0053] In one embodiment of the present application, please continue to refer to Figure 1 , the structures of at least two driving brackets are consistent, so as to facilitate the processing and preparation of the filter.

[0054] In one embodiment of the present application, please continue to refer to Figure 1 The number of the driving brackets is four, and the four driving brackets are arranged centrally and symmetrically relative to the geometric center of the upper electrode plate 31. Figure 1 As shown, the structure can be understood as the upper plate 31 is connected to the inner side of the support frame through the driving bracket in the four directions of up, down, left and right. The structure is stable and reliable and convenient for batch processing. Figure 1 It can be seen that the upper electrode plate 31 and the support frame can both be set to a rectangular shape, and can further be set to a regular shape, so as to further facilitate processing and manufacturing.

[0055] Furthermore, the four groups of piezoelectric drive supports can be centrally symmetrically distributed around the FP cavity 500, and the upper plates 31 of the four groups of piezoelectric drive arms 411 and the geometric center of the FP cavity 500 are on a vertical line. In the four groups of piezoelectric drive supports, each group of drive supports can use two groups of fully symmetrical multi-membrane layer structure drive arms 411.

[0056] In one embodiment of the present application, see Figure 2 , each driving bracket includes at least one driving sub-bracket 41; at least one driving sub-bracket 41 is respectively connected between the supporting frame and the upper plate 31 and is provided with a driving unit; Figure 2 (a) Figure 2 (b) shows the case where the number of driving sub-brackets 41 is two, Figure 2 (c) shows the case where the number of driving sub-brackets 41 is four, Figure 2 (d) shows the case where the number of driving sub-brackets 41 is three. Of course, the number of driving sub-brackets 41 can also be one or more than four. When setting the number of driving sub-brackets 41, it can be determined based on factors such as the specific structure of the driving sub-brackets 41, the size of the driving force actually required for the translation of the plate 31, the preparation cost and difficulty, etc., and no sole limitation is made here.

[0057] In one embodiment of the present application, please continue to refer to Figure 2 Each driving sub-bracket 41 includes a driving arm 411, a first connecting arm 412 and a second connecting arm 413, and a driving unit is provided on the driving arm 411; the driving arm 411 is connected to the upper plate 31 through the first connecting arm 412, and is connected to the support frame through the second connecting arm 413; this structure enables the driving arm 411 to be connected to the upper plate 31 and the support frame through the first connecting arm 412 and the second connecting arm 413, respectively, which is helpful for the structural design of the driving arm 411, and the driving arm 411 can be set to Figure 2 The structure shown in (d) (the two ends of the structure can be understood as the first connecting arm 412 and the second connecting arm 413) can also be set as Figure 2 (a) Figure 2 (b) Figure 2 (c) and other structures that can be opened (this structure can satisfy the upper electrode plate 31 with a larger deflection angle), and can also be set as Figure 2 Structure other than that shown.

[0058] In one embodiment of the present application, see Figure 3 The driving arm 411 is provided with a first extension arm 4111 and a second extension arm 4112. The first extension arm 4111 and the second extension arm 4112 each have a connecting end 1a and a free end 1b opposite to each other. The connecting end 1a of the first extension arm 4111 and the connecting end 1a of the second extension arm 4112 are connected to each other. The free end 1b of the first extension arm 4111 is connected to the first connecting arm 412. The free end 1b of the second extension arm 4112 is connected to the second connecting arm 413. The first extension arm 4111 and the second extension arm 4112 are both configured as driving units and can move along opposite directions. It should be noted that the first extension arm 4111 and the second extension arm 4112 can be opened away from each other in opposite directions, which can be achieved by the design of the driving unit of the first extension arm 4111 and the second extension arm 4112. From the above content, it can be seen that the installation position of the non-piezoelectric layer 4 affects the bending direction of the driving unit. The installation positions of the non-piezoelectric layer 4 of the first extension arm 4111 and the second extension arm 4112 can be set to be opposite, so that the first extension arm 4111 and the second extension arm 4112 can be opened away from each other in opposite directions. This structure can make the upper plate 31 have a larger translation amplitude, further making the filter of the present application applicable to a wider range of fields and scenarios.

[0059] In one embodiment of the present application, please refer to Figures 4 to 6Before they are opened away from each other, the first extension arm 4111 and the second extension arm 4112 extend in the same plane, and are perpendicular to the same plane in opposite directions. This structure can further enable the upper electrode plate 31 to have a larger translation amplitude. At the same time, the structure is simple, easy to process and manufacture, and the translation process of the upper electrode plate 31 is more stable and reliable.

[0060] In one embodiment of the present application, see Figure 3 The first extension arm 4111 and the second extension arm 4112 of the driving arm 411 are configured to be combined into a U shape. The structure is simple and easy to implement, and the connection between the first extension arm 4111 and the second extension arm 4112 has a smooth transition, which reduces fatigue stress, increases the service life of the driving arm 411, and has a stable and reliable structure.

[0061] In one embodiment of the present application, see Figure 3 The first connecting arms 412 of the driving sub-bracket 41 of the same driving bracket are all connected to the middle of the connected edge 50 of the upper pole plate 31, and the second connecting arms 413 are all connected to the middle of the connected edge 80 of the supporting frame. On the one hand, the first connecting arms 412 of the driving sub-bracket 41 of the same driving bracket can concentrate on effectively and smoothly transmitting the driving force to the upper pole plate 31 to enable it to translate stably; on the other hand, it can ensure that the driving sub-bracket 41 of the same driving bracket is more stably stressed when moving between the upper pole plate 31 and the supporting frame, and the overall structural stability is strong.

[0062] In one embodiment of the present application, see Figure 1 Each second connecting arm 413 is connected to the supporting frame via a planar electrode 60 .

[0063] In one embodiment of the present application, see Figure 6The first extension arm 4111 and the second extension arm 4112 are both formed by extending a telescopic layer 600 and two non-piezoelectric layers 4; the telescopic layers 600 of the first extension arm 4111 and the second extension arm 4112 have a first extension segment 21 close to their respective connection ends 1a and a second extension segment 20 close to their respective free ends 1b; the two non-piezoelectric layers 4 of the first extension arm 4111 are respectively attached to the opposite sides of its telescopic layer 600, and are respectively covered on the first extension segment 21 and the second extension segment 20 of the telescopic layer 600; the two non-piezoelectric layers 4 of the second extension arm 4112 are respectively attached to the opposite sides of its telescopic layer 600, and are respectively covered on the first extension segment 21 and the second extension segment 20 of the telescopic layer 600; the first extension segments 21 of the telescopic layers 600 of the first extension arm 4111 and the second extension arm 4112 are bent towards each other. It should be explained that bending towards each other means bending in the direction of each other. This structure not only ensures the large-scale translation of the upper electrode plate 31, but also can further reduce the stress at the connection between the first extension arm 4111 and the second extension arm 4112. The structure is reasonable, stable and easy to implement. For ease of understanding, the multi-layer driving arm 411 is similar to a sandwich structure composed of a non-piezoelectric layer 4, a bottom electrode 5, a piezoelectric layer 6, a top electrode 7 and another non-piezoelectric layer 8. Figure 5 shown.

[0064] In one embodiment of the present application, please continue to refer to Figure 6 The telescopic layers 600 of the first extension arm 4111 and the second extension arm 4112 both have a middle section 30 covered by two non-piezoelectric layers. By setting this structure, the bending deformation critical part of the telescopic layers 600 of the first extension arm 4111 and the second extension arm 4112 can be better protected and transitioned, thereby improving the structural stability and service life of the first extension arm 4111 and the second extension arm 4112.

[0065] In one embodiment of the present application, see Figure 3 Each driving bracket includes two driving sub-brackets 41. The two driving sub-brackets 41 are symmetrical structures with the center line 100 of the upper plate 31 as the symmetry axis. The center line 100 of the upper plate 31 can be understood as the symmetry axis of the upper plate 31. Figure 1 When the upper plate 31 is a square, there are two center lines 100. If the upper plate 31 is a circle, there may be several center lines 100. In this case, the two driving sub-brackets 41 may also be a symmetrical structure with the center line 100 of the circular upper plate 31 as the symmetry axis. This symmetrical structure is easy to process and implement, and the two driving sub-brackets 41 have good balance consistency during the process of applying driving force to the upper plate 31, which helps to achieve stable and reliable deflection of the upper plate 31.

[0066] On the other hand, the present application also proposes a method for preparing an FP cavity filter based on the piezoelectric effect, which may specifically include: forming a non-piezoelectric layer 4, a bottom electrode 5, a piezoelectric layer 6, a top electrode 7 and another non-piezoelectric layer 8 layer by layer from bottom to top on the top surface of the SOI silicon wafer to constitute a driving unit; forming a first reflective layer 9 on the top surface of the SOI silicon wafer; forming a cavity located below the first reflective layer 9 on the bottom surface of the SOI silicon wafer; forming a second reflective layer 11 on the base silicon wafer 10; bonding the SOI silicon wafer to the base silicon wafer 10 so that the cavity is formed into a Fabry-Perot resonant cavity 500 jointly defined by the first reflective layer 9 and the second reflective layer 11; etching the top surface of the SOI silicon wafer to form an upper electrode plate 31 provided with a first reflective layer 9, and suspending the upper electrode plate 31 under the support of the driving component; the driving component is provided with the above-mentioned driving unit.

[0067] As a specific implementation, see Figure 7 The manufacturing method of the FP cavity filter can adopt silicon-based semiconductor preparation technology, mainly including photolithography, sputtering, stripping, chemical vapor deposition, etching, bonding and other processes. The preparation process flow is as follows: Figure 7 (a)-(m) are shown below:

[0068] Step 1: Use a six-inch silicon-on-insulator (SOI) wafer as a substrate to fabricate the front cavity surface of the FP cavity MEMS with an upper electrode plate 31. Use the SCA cleaning process to clean the surface of the SOI silicon wafer, such as Figure 7 As shown in (a); wherein the thickness of the substrate silicon 1 is about 300μm-600μm, the thickness of the oxide buried layer 2 (SiO2) is about 0.5μm-2μm, and the thickness of the top silicon 3 is about 10μm-60μm; the substrate silicon 1, the oxide buried layer 2, and the top silicon 3 together constitute an SOI silicon wafer.

[0069] Step 2, positive-sequence SiO2 (non-piezoelectric layer 4) growth, using plasma enhanced chemical vapor deposition (PECVD) method to grow a layer of SiO2 layer on the surface of a six-inch wafer (i.e., SOI silicon wafer, whose cross-section includes but is not limited to a circle, and the cross-sectional shape can be selected according to actual needs) as the positive-sequence SiO2 of the piezoelectric drive arm, the film thickness is about 1μm~2μm.

[0070] Step 3: The first photolithography is performed using positive photoresist AZ5214. A series of photolithography processes such as coating, photolithography, and development are performed on the surface of the SOI substrate on which SiO2 is grown, so that the areas where SiO2 needs to be removed are exposed and the areas where SiO2 does not need to be removed are covered with photoresist.

[0071] Step 4: Etch the positive-sequence SiO2 of the driving arm using a wet etching process; the photolithographic wafer can be etched with a buffered oxide etchant (BOE) to remove the SiO2 not covered by the photoresist, and a positive-sequence SiO2 pattern layer (i.e., non-piezoelectric layer 4) is obtained after etching. Figure 7 (b) as shown.

[0072] Step 5: Second photolithography, using AZ5214 as reverse glue after two exposures. The first exposure requires a photolithography mask, and the second exposure is maskless flood exposure. At the same time, negative photoresist can also be used for one mask exposure. The photoresist on the piezoelectric drive arm is removed, and the other places are covered with photoresist.

[0073] Step 6: Growth of the bottom electrode 5: electron beam evaporation or magnetron sputtering is used to deposit a layer of Mo as the bottom electrode 5 on the surface of the wafer, and the film thickness is about 0.1 μm to 0.2 μm.

[0074] Step 7, Mo metal stripping, the wafer is placed in acetone and soaked, ultrasonicated, and then cleaned with anhydrous ethanol and deionized water in turn, and dried; after the stripping is completed, the bottom electrode 5 of the piezoelectric drive arm is formed, as shown in FIG. Figure 7 (c) as shown.

[0075] Step 8: Growth of piezoelectric film: metal organic chemical vapor deposition (MOCVD) is used to deposit a layer of AlN as a piezoelectric film on the surface of the wafer, and the film thickness is about 1 μm to 2 μm.

[0076] Step 9: The third photolithography is performed. Through the photolithography process, the photoresist on the piezoelectric drive arm is left, and the photoresist in other places is completely removed.

[0077] Step 10: Wet etching of the piezoelectric film: wet etching of AlN with phosphoric acid (H3PO4) solution to completely remove the AlN outside the piezoelectric drive arm, leaving the AlN (piezoelectric layer 6) on the piezoelectric drive arm. Figure 7 (d) as shown.

[0078] Step 11, the fourth photolithography, using AZ5214 as a reverse glue after two exposures, the first exposure requires a photolithography mask, the second exposure is a maskless flood exposure; at the same time, negative photoresist can also be used for a single mask exposure. The photoresist on the piezoelectric drive arm is removed, and the other places are covered with photoresist.

[0079] Step 12: Growth of the top electrode 7: electron beam evaporation or magnetron sputtering is used to deposit a layer of Mo as the top electrode 7 on the surface of the wafer, and the film thickness is about 0.1 μm to 0.2 μm.

[0080] Step 13, the top electrode 7Mo metal is stripped, the wafer is placed in acetone and soaked, ultrasonicated, and then cleaned with anhydrous ethanol and deionized water in turn, and dried; after the stripping is completed, the top electrode 7 of the piezoelectric drive arm is formed, as shown in FIG. Figure 7 (e) as shown.

[0081] Step 14: Growth of reversed SiO2 (another non-piezoelectric layer 8). A PECVD process is used to grow SiO2 on the surface of the wafer to be used as reversed SiO2 for the piezoelectric drive arm. The thickness of the reversed SiO2 is about 1 μm-2 μm.

[0082] Step 15, the fifth photolithography, through the photolithography process, the photoresist in the place where the reversed SiO2 needs to be removed is removed, and the place where the SiO2 needs to be left is covered with photoresist.

[0083] Step 16, reverse SiO2 etching, using a dry etching process to etch the SiO2 not covered by the photoresist, and after etching, another non-piezoelectric layer 8 is obtained, such as Figure 7 (f) as shown.

[0084] Step 17, the sixth photolithography, through the photolithography process, the photoresist is removed from the place where the top silicon 3 needs to be removed, and the rest of the place is covered by the photoresist.

[0085] Step 18: etching the Si on the front cavity surface, using a dry etching process to etch the Si not covered by the photoresist. Figure 7 (g) as shown.

[0086] Step 19, the seventh photolithography, through the photolithography process, the photoresist is removed from the place where the top silicon 3 is removed, and the rest of the place is covered with photoresist.

[0087] Step 20, the front cavity surface Bragg reflection surface (first reflection layer 9) is deposited by magnetron sputtering, and high refractive index and low refractive index materials are alternately deposited, wherein the high refractive index material is prepared by magnetron sputtering TiO2 target material, or Ta2O5 target material, or Nb2O5 target material, or SiN target material to prepare TiO2 film, or Ta2O5 film, or Nb2O5 film, or SiN film; the low refractive index material is deposited by PECVD SiO2 film.

[0088] Step 21, the front cavity surface Bragg reflection surface is peeled off, the wafer is placed in acetone and soaked, ultrasonicated, and then washed with anhydrous ethanol and deionized water in turn, and dried; the first reflection layer 9 is formed, and after the peeling is completed, Figure 7 (h) shown.

[0089] Step 22 , the eighth photolithography process is performed on the back side of the SOI wafer to define the area of ​​the FP cavity 500 that needs to be etched.

[0090] Step 23, using DRIE deep silicon etching process, etching the wafer from the back side, etching the substrate silicon 1 to the middle SiO2 layer; then, using SiO2 etching equipment, etching the SiO2 in the middle of the wafer, and after etching, Figure 7 (i) as shown.

[0091] Step 24: Use a six-inch silicon wafer as the back cavity surface of the FP cavity 500 to manufacture the MEMS back cavity surface of the FP cavity 500 with a Bragg reflection layer. Use the RCA cleaning process to clean the surface of the base silicon wafer 10, such as Figure 7 (g) shows that the thickness of the silicon wafer 10 is about 300μm-600μm.

[0092] Step 25, ninth photolithography, through the photolithography process, define the position of the rear cavity surface Bragg reflection layer (second reflection layer 11) of the FP cavity 500, remove the photoresist where the Bragg reflection layer is needed, and cover the rest with photoresist.

[0093] Step 26, rear cavity surface Bragg reflection surface deposition, using magnetron sputtering to alternately deposit high refractive index and low refractive index materials, wherein the high refractive index material is prepared by magnetron sputtering TiO2 target material, or Ta2O5 target material, or Nb2O5 target material, or SiN target material to prepare TiO2 film, or Ta2O5 film, or Nb2O5 film, or SiN film; the low refractive index material is deposited by PECVD SiO2 film.

[0094] Step 27, the back cavity surface Bragg reflection surface is peeled off, the wafer is placed in acetone and soaked, ultrasonicated, and then washed with anhydrous ethanol and deionized water in turn, and dried; the second reflection layer 10 is formed, and after the peeling is completed, Figure 7 (k) as shown.

[0095] Step 28, wafer bonding, bonding the SOI wafer with the front cavity surface and the wafer with the back cavity surface to form an integral chamber, such as Figure 7 (l) as shown.

[0096] Step 29, the front side of the wafer is released, and the front side of the wafer is etched; the unnecessary top silicon 3 is etched away, and at this time, the front cavity surface with the Bragg reflection layer will be in a suspended state under the support of the piezoelectric drive arm, such as Figure 7 (m) shown.

[0097] Step 30: Slicing: using laser scribing to cut the prepared wafer into single core particles.

[0098] Step 31: Pressure welding and packaging.

[0099] Step 32: Chip testing.

[0100] It can be seen that a specific embodiment of the piezoelectric driven FP cavity filter proposed in the present application can be divided into a rear cavity surface with a Bragg reflection layer, a front cavity surface with a Bragg reflection layer, and then the two cavity surfaces are bonded together to form the middle FP cavity 500. The front cavity surface of the FP cavity 500 has an upper electrode plate 31 in the middle of the hollow area, and four groups of piezoelectric driving arms 411 are connected around it. The four groups of piezoelectric driving arms 411 connect the upper electrode plate 31 and the side of the FP cavity 500 to form a movable upper electrode plate 31, which can move up and down under the drive of piezoelectricity, thereby changing the size of the FP cavity 500.

[0101] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the implementation methods of the present application. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation methods here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A FP cavity filter based on piezoelectric effect, characterized in that: include: Support frame; Upper plate; The first reflection layer and the second reflection layer are both arranged in the support frame and are always parallel to each other, so as to jointly define a Fabry-Perot resonant cavity; the first reflection layer is arranged on the upper plate; A driving assembly connected between the upper plate and the supporting frame, wherein a driving unit is provided in the driving assembly; The driving unit is formed by combining a telescopic layer and at least one non-piezoelectric layer, wherein the telescopic layer includes a piezoelectric layer, a bottom electrode located at the bottom of the piezoelectric layer, and a top electrode located at the top of the piezoelectric layer; The at least one non-piezoelectric layer is configured to be fitted on the bottom electrode and / or the top electrode so that after the electric field between the bottom electrode and the top electrode changes, the piezoelectric layer either stretches and drives the at least one non-piezoelectric layer to bend in the opposite direction to the side where the non-piezoelectric layer is located, or shortens and drives the at least one non-piezoelectric layer to bend in the direction where the non-piezoelectric layer is located, thereby driving the upper electrode to move away from or toward the second reflective layer to change the size of the Fabry-Perot resonant cavity.

2. The FP cavity filter according to claim 1, characterized in that: The driving assembly includes at least two driving brackets, which are respectively connected between the supporting frame and the upper plate and are both provided with the driving unit, wherein there is at least one pair of the driving brackets respectively arranged on opposite sides of the upper plate.

3. The FP cavity filter according to claim 2, characterized in that: The structures of the at least two driving brackets are consistent; and / or, the number of the driving brackets is four, and the four driving brackets are arranged in a centrally symmetrical manner relative to the geometric center of the upper electrode plate.

4. The FP cavity filter according to claim 2 or 3, characterized in that: Each of the driving brackets includes at least one driving sub-bracket; the at least one driving sub-bracket is respectively connected between the supporting frame and the upper plate and is provided with the driving unit.

5. The FP cavity filter according to claim 4, characterized in that: Each of the driving sub-brackets includes a driving arm, a first connecting arm and a second connecting arm, and the driving unit is provided on the driving arm; the driving arm is connected to the upper pole plate through the first connecting arm, and is connected to the supporting frame through the second connecting arm.

6. The FP cavity filter according to claim 5, characterized in that: The driving arm is provided with a first extension arm and a second extension arm, each of the first extension arm and the second extension arm has a relative connecting end and a free end, the connecting end of the first extension arm and the connecting end of the second extension arm are connected to each other, the free end of the first extension arm is connected to the first connecting arm, and the free end of the second extension arm is connected to the second connecting arm; the first extension arm and the second extension arm are both configured as the driving unit and can be opened away from each other in opposite directions.

7. The FP cavity filter according to claim 6, characterized in that: Before being opened away from each other, the first extension arm and the second extension arm extend in the same plane, and the opposite direction is perpendicular to the same plane; and / or, the first extension arm and the second extension arm of the driving arm are configured to be combined into a U-shape; And / or, the first connecting arms of the driving sub-brackets of the same driving bracket are all connected to the middle of the connected edge of the upper plate, and the second connecting arms are all connected to the middle of the connected edge of the supporting frame; And / or, each of the second connecting arms is connected to the supporting frame via a planar electrode; And / or, the first extension arm and the second extension arm are both formed by extending a combination of one telescopic layer and two non-piezoelectric layers; the telescopic layers of the first extension arm and the second extension arm each have a first extension segment close to their respective connection ends and a second extension segment close to their respective free ends, the two non-piezoelectric layers of the first extension arm are respectively attached to the opposite sides of its telescopic layer, and respectively cover the first extension segment and the second extension segment of the telescopic layer; the two non-piezoelectric layers of the second extension arm are respectively attached to the opposite sides of its telescopic layer, and respectively cover the first extension segment and the second extension segment of the telescopic layer; the first extension segments of the telescopic layers of the first extension arm and the second extension arm are bent toward each other.

8. The FP cavity filter according to claim 7, characterized in that: The telescopic layers of the first extension arm and the second extension arm both have a middle section covered by two non-piezoelectric layers at the same time.

9. The FP cavity filter according to claim 4, characterized in that: Each of the driving brackets includes two driving sub-brackets, and the two driving sub-brackets are symmetrical structures with the center line of the upper pole plate as the symmetry axis.

10. A method for preparing the FP cavity filter according to any one of claims 1 to 9, comprising: The non-piezoelectric layer, the bottom electrode, the piezoelectric layer, the top electrode and another non-piezoelectric layer are formed layer by layer from bottom to top on the top surface of the SOI silicon wafer to form the driving unit; forming the first reflective layer on the top surface of the SOI silicon wafer; forming a chamber located below the first reflective layer on the bottom surface of the SOI silicon wafer; forming the second reflective layer on the base silicon wafer; Bonding the SOI silicon wafer and the substrate silicon wafer so that the chamber is formed into the Fabry-Perot resonant cavity defined by the first reflective layer and the second reflective layer; The top surface of the SOI silicon wafer is etched to form the upper plate provided with the first reflective layer, and the upper plate is suspended in the air under the support of the driving component; the driving unit is provided in the driving component.

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