MEMS Fabry-Perot filter and preparation method thereof

Abstract

The invention relates to the technical field of filtering, in particular to an MEMS Fabry-Perot filter and a preparation method thereof. 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 first electric heating layer. The telescopic layer comprises a second electric heating layer, a resistive layer, a first insulating layer located between the resistive layer and the second electric heating layer, and a second insulating layer located on the side, away from the second electric heating layer, of the resistive layer. The thermal expansion coefficient of the first electric heating layer is smaller than that of the second electric heating layer, and the at least one first electric heating layer is attached to the second electric heating layer and / or the second insulating layer. The electrothermal 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 MEMS Fabry-Perot filter and a method for preparing the MEMS Fabry-Perot filter. Background Art

[0002] MEMS (Micro-Electro-Mechanical System) Fabry-Perot (FP) filter, referred to as MEMS-FP filter in this article. MEMS-FP filter uses the principle of micro-nano structure to control optical parameters such as interference, diffraction and dispersion to achieve filtering effect. By changing the size, shape and material characteristics of the micro-nano structure, the filtering performance can be customized. 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 MEMS-FP filter, make the optical wavelength linearly adjustable in a large 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 MEMS Fabry-Perot filter and a method for manufacturing the MEMS Fabry-Perot filter.

[0004] According to one aspect of the present application, a MEMS Fabry-Perot filter is provided, comprising a support frame; an upper plate; a first reflective layer and a second reflective layer, both of which are arranged in the support frame and are always parallel to each other, so as to jointly define a Fabry-Perot resonant cavity; the first reflective layer is arranged in the upper plate; a driving component, connected between the upper plate and the support 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 first electric heating layer, wherein the telescopic layer comprises a second electric heating layer, a resistance layer, a first insulating layer between the resistance layer and the second electric heating layer, and a first insulating layer behind the resistance layer. a second insulating layer on the side of the second electric heating layer; the thermal expansion coefficient of the first electric heating layer is smaller than the thermal expansion coefficient of the second electric heating layer, and the at least one first electric heating layer is configured to be fitted on the second electric heating layer and / or the second insulating layer, so that after the electric field of the resistance layer changes, the second electric heating layer either stretches and drives the at least one first electric heating layer to bend in the opposite direction of the side where the first electric heating layer is located, or shortens and drives the at least one first electric heating layer to bend in the direction where the first electric heating layer is located, thereby driving the upper electrode plate to move away from or toward the second reflecting layer to change the size of the Fabry-Perot resonant cavity.

[0005] In addition to one or more features described herein, or as an alternative, a further embodiment of the MEMS Fabry-Perot filter may include that the driving component includes at least two driving brackets, and the at least two driving brackets are respectively connected between the supporting frame and the upper plate and are each provided with the driving unit, wherein there is at least a pair of the driving brackets respectively arranged on opposite sides of the upper plate.

[0006] In addition to or instead of one or more features described herein, further embodiments of the MEMS Fabry-Perot 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 MEMS Fabry-Perot 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 MEMS Fabry-Perot 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 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 MEMS Fabry-Perot 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 instead of one or more features described herein, further embodiments of the MEMS Fabry-Perot 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 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 telescopic layer and two first electric heating layers in combination; the telescopic layers of the first extension arm and the second extension arm have a first extension section close to their respective connection ends and a second extension section close to their respective free ends, the two first electric heating layers of the first extension arm are respectively attached to the opposite sides of its telescopic layer, and respectively cover the first extension section and the second extension section of the telescopic layer; the two first electric heating layers of the second extension arm are respectively attached to the opposite sides of its telescopic layer, and respectively cover the first extension section and the second extension section of the telescopic layer; the first extension sections 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, a further embodiment of the MEMS Fabry-Perot filter may include that the telescopic layers of the first extension arm and the second extension arm both have a middle section that is covered by two first electrothermal layers at the same time.

[0012] In addition to or instead of one or more features described herein, a further embodiment of the MEMS Fabry-Perot 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 axis of symmetry.

[0013] According to another aspect of the present application, a method for preparing a MEMS Fabry-Perot filter is provided, comprising: forming the first electric heating layer, the first insulating layer, the resistance layer, the second insulating layer, the second electric heating layer and another first electric heating 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 reflecting layer on the top surface of the SOI silicon wafer; forming a cavity located below the first reflecting layer on the bottom surface of the SOI silicon wafer; forming the second reflecting layer on a base silicon wafer; bonding the SOI silicon wafer to the base silicon wafer so that the cavity is formed into the Fabry-Perot resonant cavity defined by the first reflecting layer and the second reflecting layer; etching the top surface of the SOI silicon wafer to form the upper plate provided with the first reflecting layer, and suspending the upper plate in the air 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 an electrothermal driven MEMS Fabry-Perot 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 first electrothermal layer, and the electrothermal drive 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 have 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 a MEMS Fabry-Perot 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 in at least one embodiment of the present application;

[0023] Figure 7 It is a process schematic diagram of a method for preparing a MEMS Fabry-Perot 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: First electric heating layer

[0027] 5: Resistance layer 6: Second electric heating layer

[0028] 7: Another first electric heating layer 8: First reflective layer

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

[0030] 60: Planar electrode 31: Upper electrode

[0031] 41: Driving sub-bracket 411: Driving arm

[0032] 412: first connecting arm 413: second connecting arm

[0033] 4111: first extension arm 4112: second extension arm

[0034] 1a: Connecting end 1b: Free end

[0035] 50: connected edge of the upper plate 80: connected edge of the support frame

[0036] 20: Second extension section 30: Middle section

[0037] 21: First extension section 500: FP cavity

[0038] 100: center line 600: telescopic layer

[0039] 11: First insulation layer 12: Second insulation layer 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 7Taking the example, a MEMS Fabry-Perot filter provided by the present application is described and introduced. A MEMS Fabry-Perot filter provided by the present application includes a support frame, an upper plate 31, a first reflective layer 8 and a second reflective layer 10, all of which are 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 8 is arranged on the upper plate 31; a driving component is connected between the upper plate 31 and the support frame, and a driving unit is arranged in the driving component; the driving unit is formed by combining a telescopic layer 600 and at least one first electric heating layer 4, and the telescopic layer 600 includes a second electric heating layer 6, a resistance layer 5, a first insulating layer 11 located between the resistance layer 5 and the second electric heating layer 6, and a first insulating layer 11 located between the resistance layer 5 and the second electric heating layer 6. A second insulating layer 12 facing away from the side of the second electric heating layer 6; the thermal expansion coefficient of the first electric heating layer 4 is smaller than the thermal expansion coefficient of the second electric heating layer 6, and at least one first electric heating layer 4 is configured to be fitted on the second electric heating layer 6 and / or the second insulating layer 12, so that after the electric field of the resistance layer 5 changes, the second electric heating layer 6 either stretches and drives at least one first electric heating layer 4 to bend in the opposite direction of the side where the first electric heating layer 4 is located, or shortens and drives at least one first electric heating layer 4 to bend in the direction where the first electric heating layer 4 is located, thereby driving the upper electrode plate 31 to move away from or toward the second reflecting layer 10 to change the size of the Fabry-Perot resonant cavity 500.

[0046] It should be explained that the coefficient of thermal expansion refers to the rate of change of the length or volume of an object when the temperature changes. For solid substances, the coefficient of thermal expansion usually refers to the change in length caused by a unit temperature change under constant pressure conditions. Materials with high coefficients of thermal expansion can expand or contract more when the temperature rises.

[0047] It should be noted that the thermal expansion coefficient of the first electric heating layer 4 is smaller than that of the second electric heating layer 6 , which can be understood as the length change of the first electric heating layer 4 is smaller than that of the second electric heating layer 6 during the heating or cooling process.

[0048] Take a specific implementation as an example. Figure 5 As shown, at this time, the second electric heating layer 6 will shrink after the resistance layer 5 is energized and heated, and the thermal expansion coefficient of the second electric heating layer 6 is greater than the thermal expansion coefficient of the first electric heating layer 4, resulting in a faster diffusion rate of the second electric heating layer 6 when heated, resulting in shrinkage, driving the first electric heating layer 4 to undergo the following 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 10 during translation, the arrangement and attachment of the first electric heating layer 4 and the second electric heating layer 6, as well as the expansion or contraction of the second electric heating layer 6 after heating, are not specifically limited.

[0050] The present application proposes an electrothermal driven MEMS Fabry-Perot filter in which an upper plate 31 always moves parallel to the second reflective layer 10, which can keep the first reflective layer 8 and the second reflective layer 10 always parallel, and by setting a driving component including a driving unit, the upper plate 31 can have a large range of movement, 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 first electrothermal layer 4, and the electrothermal drive 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 have 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 thermal expansion coefficient of the first electric heating layer 4 is less than that of the second electric heating layer 6. The first electric heating layer 4 can be made of a low expansion coefficient material, and the second electric heating layer 6 can be made of a high expansion coefficient material; the low expansion coefficient material can be silicides such as silicon oxide and silicon nitride, and metal oxides such as aluminum oxide and titanium oxide. The high thermal expansion coefficient material can be metals such as Al and gold, and alloys. The heating resistor can be a metal material with relatively large resistance such as Pt and Ti. The Bragg reflection layer is a multi-layer material, mainly composed of TiO2, Ta2O5, Nb2O5 or SiN thin film high refractive index materials, and low refractive index materials such as SiO2 alternately compounded.

[0052] In one embodiment of the present application, see Figure 1 The 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 the opposite sides of the upper electrode plate 31; such an arrangement allows driving brackets to be arranged on the 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 acts on the changing electric field of the resistance layer 5, 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 electrothermal drive brackets can be centrally symmetrically distributed around the FP cavity 500, and the upper plates 31 of the four groups of electrothermal drive arms 411 and the geometric center of the FP cavity 500 are on a vertical line. In the four groups of electrothermal drive brackets, each group of drive brackets can use two groups of fully symmetrical multi-film 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 3The 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 in 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 form 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 first electric heating layer 4 affects the bending direction of the driving unit. The installation positions of the first electric heating 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, and further make the filter of the present application applied to a wider range of fields and scenarios.

[0059] In one embodiment of the present application, please refer to Figures 4 to 6 Before 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 6 The first extension arm 4111 and the second extension arm 4112 are both formed by extending a telescopic layer 600 and two first electric heating 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 first electric heating layers 4 of the first extension arm 4111 are respectively attached to the opposite sides of its telescopic layer 600, and are respectively covered with the first extension segment 21 and the second extension segment 20 of the telescopic layer 600; the two first electric heating layers 4 of the second extension arm 4112 are respectively attached to the opposite sides of its telescopic layer 600, and are respectively covered with 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 and stable and easy to implement. For ease of understanding, the multi-layer driving arm 411 is similar to a sandwich structure composed of a low thermal expansion coefficient material, a heating resistor material, an upper and lower insulating layer material, and a high thermal expansion coefficient material. 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 first electric heating layers 4. 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 1When 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 a MEMS Fabry-Perot filter, which may specifically include: forming a first electric heating layer 4, a first insulating layer 11, a resistance layer 5, a second insulating layer 12, a second electric heating layer 6 and another first electric heating layer 7 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 8 on the top surface of the SOI silicon wafer; forming a cavity located below the first reflective layer 8 on the bottom surface of the SOI silicon wafer; forming a second reflective layer 10 on the base silicon wafer; bonding the SOI silicon wafer to the base silicon wafer so that the cavity is formed into a Fabry-Perot resonant cavity 500 jointly defined by the first reflective layer 8 and the second reflective layer 10; etching the top surface of the SOI silicon wafer to form an upper plate 31 provided with a first reflective layer 8, and suspending the upper 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 MEMS Fabry-Perot filter can adopt a silicon-based semiconductor manufacturing process, which mainly includes photolithography, sputtering, stripping, chemical vapor deposition, etching, bonding and other processes. The manufacturing process flow is as follows: Figure 7 (a)-(m) are shown below:

[0068] Step 1: Use a six-inch silicon-on-insulator (SOI) 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 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 (first electric heating layer 4) growth. A layer of SiO2 is grown on the surface of a six-inch wafer (it should be explained that the SOI silicon wafer is simply referred to as a wafer here, and its cross section is not limited to a circle) by plasma enhanced chemical vapor deposition (PECVD) as the positive-sequence SiO2 of the driving arm 411, and the film thickness is about 1 μm-2 μm.

[0070] Step 3: The first photolithography uses positive photoresist AZ5214; through a series of photolithography processes such as coating, photolithography, and development on the SOI substrate on which SiO2 is grown, the areas where SiO2 needs to be removed are exposed, and the areas where no removal is required are covered with photoresist.

[0071] Step 4: Etch the positive-sequence SiO2 of the driving arm 411 by wet etching process; the wafer after photolithography can be etched by buffered oxide etchant (BOE) to remove the SiO2 not covered by the photoresist, and obtain the positive-sequence SiO2 pattern layer (first electric heating layer 4) after etching. Figure 7 (b) as shown.

[0072] Step 5: The first insulating silicon oxide (first insulating layer 11) is grown by plasma enhanced chemical vapor deposition (PECVD) to grow a thin layer of SiO2 on the surface of the wafer after SiO2 etching, and the film thickness is about 0.01 μm-0.1 μm.

[0073] Step 6, the second photolithography, using AZ5214 as a 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.

[0074] Step 7: Prepare the heating resistor (resistance layer 5) of the driving arm 411 by magnetron sputtering, and sputtering targets such as Pt and Ti can be used; a layer of Pt or Ti film is sputtered on the surface of the wafer after photolithography as the heating resistor of the electrothermal driving arm 411, and its thickness is about 0.05μm-0.15μm.

[0075] Step 8, Pt stripping process, the six-inch wafer is placed in acetone and soaked, ultrasonicated, and then cleaned with anhydrous ethanol and deionized water in turn, and dried; the resistance layer 5 of the electric heating drive arm 411 is formed, and after the stripping is completed, Figure 7 (c) as shown.

[0076] Step 9: Second insulating silicon oxide (second insulating layer 12) growth is performed. A thin layer of SiO2 is grown on the surface of the wafer as an insulating layer by plasma enhanced chemical vapor deposition (PECVD) to cover the heating resistor. The film thickness is about 0.01 μm-0.1 μm.

[0077] Step 10, the third photolithography, using AZ5214 as a reverse glue after two exposures, the first exposure requires a photolithography mask, and the second exposure is a maskless flood exposure; at the same time, a negative photoresist can also be used for a single mask exposure.

[0078] Step 10, depositing an Al film (the second electric heating layer 6), using electron beam evaporation or magnetron sputtering to grow a layer of Al on the surface of the wafer as the Al (the second electric heating layer 6) on the electric heating drive arm 411, and the electrode lead of the electric heating drive arm 411, the thickness of which is about 1μm-2μm.

[0079] Step 11, Al stripping process, the wafer is placed in acetone and soaked, ultrasonicated, and then cleaned with anhydrous ethanol and deionized water in turn, and dried; the electrothermally driven Al and lead (the second electrothermal layer 6) are formed, and after the stripping is completed, Figure 7 (d) as shown.

[0080] Step 12, growth of reversed SiO2 (another first electrothermal layer 7), using PECVD process to grow SiO2 on the surface of the wafer once to be used as reversed SiO2 of the electrothermal drive arm 411, with a thickness of about 1 μm-2 μm.

[0081] Step 13, the fourth 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.

[0082] Step 14: Inverse SiO2 is etched by dry etching process to etch the SiO2 not covered by the photoresist, and an inverse SiO2 layer (another first electric heating layer 7) is obtained after etching. Figure 7 (e) as shown.

[0083] Step 15, the fifth photolithography, through the photolithography process, the photoresist in the place where the top silicon 3 needs to be removed is removed, and the rest of the place is covered by the photoresist.

[0084] Step 16: front cavity Si etching, using dry etching process to etch the Si not covered by photoresist. Figure 7 (f) as shown.

[0085] Step 17, the fifth 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.

[0086] Step 18, the front cavity surface Bragg reflection surface (first reflection layer 8) 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.

[0087] Step 18, the front cavity Bragg reflection surface (first reflection layer 8) is peeled off, the wafer is placed in acetone and soaked, ultrasonicated, and then cleaned with anhydrous ethanol and deionized water in turn, and dried; the first reflection layer 8 is formed, and after the peeling is completed, Figure 7 (g) as shown.

[0088] Step 19, the sixth 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.

[0089] Step 20, 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 (h) shown.

[0090] Step 21: Use a six-inch silicon wafer (substrate silicon wafer 9) as the back cavity surface of the FP cavity 500 to manufacture a FP cavity MEMS back cavity surface with a Bragg reflection layer (second reflection layer 10). Use the SCA cleaning process to clean the silicon wafer surface, such as Figure 7 (i) shown; wherein the thickness of the base silicon wafer 9 is about 300μm-600μm.

[0091] Step 22, seventh photolithography, through the photolithography process, define the position of the Bragg reflection layer (second reflection layer 10) on the rear cavity surface of the FP cavity, remove the photoresist where the Bragg reflection layer (second reflection layer 10) is needed, and cover the rest with photoresist.

[0092] Step 23, the back cavity surface Bragg reflection surface (second reflection layer 10) 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.

[0093] Step 24, the back cavity Bragg reflection surface (second reflection layer 10) 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 (j) as shown.

[0094] Step 25, 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 (k) as shown.

[0095] Step 26, 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 (upper electrode 31) with the Bragg reflection layer will be in a suspended state under the support of the electrothermal drive arm 411, as shown in FIG. Figure 7 (m) shown.

[0096] Step 27, dicing: using laser dicing to cut the prepared wafer into single core particles.

[0097] Step 28: Pressure welding and packaging.

[0098] Step 29: Chip testing.

[0099] It can be seen that a specific embodiment of the electrothermal driven FP cavity MEMS wavelength tunable filter proposed in the present application can be divided into a rear cavity surface with a Bragg reflection layer and 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 electrothermal drive arms 411 are connected around it. The four groups of electrothermal drive 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 electrothermal drive, thereby changing the size of the FP cavity 500.

[0100] 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 MEMS Fabry-Perot filter, 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 first electric heating layer, wherein the telescopic layer includes a second electric heating layer, a resistance layer, a first insulating layer located between the resistance layer and the second electric heating layer, and a second insulating layer located on a side of the resistance layer away from the second electric heating layer; The thermal expansion coefficient of the first electric heating layer is smaller than the thermal expansion coefficient of the second electric heating layer, and the at least one first electric heating layer is configured to be fitted on the second electric heating layer and / or the second insulating layer, so that after the electric field of the resistance layer changes, the second electric heating layer either stretches and drives the at least one first electric heating layer to bend in the opposite direction of the side where the first electric heating layer is located, or shortens and drives the at least one first electric heating layer to bend in the direction of the side where the first electric heating 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.

2. The MEMS Fabry-Perot 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 MEMS Fabry-Perot 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 MEMS Fabry-Perot 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 MEMS Fabry-Perot 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 arranged on the driving arm; the driving arm is connected to the upper plate through the first connecting arm, and is connected to the supporting frame through the second connecting arm.

6. The MEMS Fabry-Perot 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 MEMS Fabry-Perot 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 first electric heating layers; the telescopic layers of the first extension arm and the second extension arm have a first extension section close to their respective connection ends and a second extension section close to their respective free ends, the two first electric heating layers of the first extension arm are respectively attached to the opposite sides of its telescopic layer, and respectively cover the first extension section and the second extension section of the telescopic layer; the two first electric heating layers of the second extension arm are respectively attached to the opposite sides of its telescopic layer, and respectively cover the first extension section and the second extension section of the telescopic layer; the first extension sections of the telescopic layers of the first extension arm and the second extension arm are bent toward each other.

8. The MEMS Fabry-Perot 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 first electric heating layers at the same time.

9. The MEMS Fabry-Perot 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 a MEMS Fabry-Perot filter according to any one of claims 1 to 9, comprising: The first electric heating layer, the first insulating layer, the resistance layer, the second insulating layer, the second electric heating layer and another first electric heating 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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