Memsmach-zehnder filter and method of manufacturing the same

Abstract

The application relates to the technical field of filtering, in particular to a MEMS Fabry-Perot filter and a preparation method thereof. The filter comprises a support frame, an upper pole plate, a first reflection layer and a second reflection layer, which are arranged in the support frame and always parallel to each other, and are used for jointly defining a Fabry-Perot resonant cavity; a driving assembly is connected between the upper pole plate and the support 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 electrothermal layer; the telescopic layer comprises a second electrothermal layer, a resistance layer, a first insulating layer arranged between the resistance layer and the second electrothermal layer, and a second insulating layer arranged on the side of the resistance layer away from the second electrothermal layer; the thermal expansion coefficient of the first electrothermal layer is smaller than the thermal expansion coefficient of the second electrothermal layer, and the at least one first electrothermal layer is attached to the second electrothermal layer and / or the second insulating layer. The electrothermal driving structure can realize filter miniaturization, structural simplification, overall volume and weight reduction, and high device reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of filtering, in particular to a MEMS Fabry-Perot filter and a preparation method of the MEMS Fabry-Perot filter. BACKGROUND

[0002] The MEMS (Micro-Electro-Mechanical System) Fabry-Perot filter, referred to as MEMS-FP filter in the present document, realizes filtering effect by using the principle of micro-nano structure regulation of interference, diffraction and dispersion of optical parameters, and the filtering performance can be customized by changing the size, shape and material characteristics of the micro-nano structure. The filter has the advantages of strong customization ability of filtering performance, simple structure and high spatial resolution, and shows significant advantages in spectral detection. How to further simplify, miniaturize and linearly adjust a wide range of optical wavelengths of the structure of the MEMS-FP filter while ensuring high resistance to external force sensitivity and reliability has become a research hotspot. SUMMARY

[0003] In view of the above, it is desirable to provide a MEMS Fabry-Perot filter and a preparation method of 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 always parallel to each other to jointly define a Fabry-Perot resonant cavity, the first reflective layer is arranged on the upper plate, a driving assembly is connected between the upper plate and the support frame, and a driving unit is arranged in the driving assembly. The driving unit is formed by a telescopic layer and at least one first electrothermal layer. The telescopic layer includes a second electrothermal layer, a resistance layer, a first insulating layer between the resistance layer and the second electrothermal layer, and a second insulating layer on the side of the resistance layer away from the second electrothermal layer. The thermal expansion coefficient of the first electrothermal layer is less than the thermal expansion coefficient of the second electrothermal layer. The at least one first electrothermal layer is arranged to be attached to the second electrothermal layer and / or the second insulating layer, so that the second electrothermal layer bends in the opposite direction of the side where the at least one first electrothermal layer is located after the electric field of the resistance layer changes, or shortens and drives the at least one first electrothermal layer to bend towards the side where the at least one first electrothermal layer is located, thereby driving the upper plate to translate away from or towards the second reflective layer to change the size of the Fabry-Perot resonant cavity.

[0005] In addition to one or more of the features described herein, or as an alternative, further embodiments of the MEMS Fabry-Perot filter can include that the drive assembly includes at least two drive supports, each of the at least two drive supports being connected between the support frame and the upper plate and each of the at least two drive supports being provided with the drive unit, wherein at least one pair of the at least two drive supports are arranged on opposite sides of the upper plate.

[0006] In addition to one or more of the features described herein, or as an alternative, further embodiments of the MEMS Fabry-Perot filter can include that the at least two drive supports are identical in structure; and / or, the number of the drive supports is four, the four drive supports being arranged in a central symmetric manner with respect to a geometric center of the upper plate.

[0007] In addition to one or more of the features described herein, or as an alternative, further embodiments of the MEMS Fabry-Perot filter can include that each of the drive supports includes at least one drive sub-support, each of the at least one drive sub-support being connected between the support frame and the upper plate and each of the at least one drive sub-support being provided with the drive unit.

[0008] In addition to one or more of the features described herein, or as an alternative, further embodiments of the MEMS Fabry-Perot filter can include that each of the drive sub-supports includes a drive arm, a first connecting arm, and a second connecting arm, the drive arm being provided with the drive unit; the drive arm being connected to the upper plate via the first connecting arm and being connected to the support frame via the second connecting arm.

[0009] In addition to one or more of the features described herein, or as an alternative, further embodiments of the MEMS Fabry-Perot filter can include that the drive arm is provided with a first extension arm and a second extension arm, each of the first extension arm and the second extension arm having opposite connecting ends and free ends, the connecting end of the first extension arm and the connecting end of the second extension arm being connected to each other, the free end of the first extension arm being connected to the first connecting arm, and the free end of the second extension arm being connected to the second connecting arm; the first extension arm and the second extension arm being configured as the drive unit and being capable of being opened away from each other in opposite directions.

[0010] In addition to one or more of the features described herein, or as an alternative, further embodiments of the MEMS Fabry-Perot filter can include that the first extension arm and the second extension arm extend in the same plane before being splayed apart from each other, the opposite directions being perpendicular to the same plane; and / or, the first extension arm and the second extension arm of the drive arm are configured to combine into a U-shape; and / or, the first connecting arms of the drive sub-frames of the same drive frame are connected to the middle of the connected edges of the upper plate, and the second connecting arms are connected to the middle of the connected edges of the support frame; and / or, each of the second connecting arms is connected to the support frame through a planar electrode; and / or, the first extension arm and the second extension arm are formed by a telescopic layer and two first electrothermal layers; the telescopic layer of the first extension arm and the second extension arm each has a first extension section near the respective connecting end and a second extension section near the respective free end, the two first electrothermal layers of the first extension arm are respectively attached to the opposite sides of the telescopic layer and respectively cover the first extension section and the second extension section of the telescopic layer; the two first electrothermal layers of the second extension arm are respectively attached to the opposite sides of the telescopic layer and respectively cover the first extension section and the second extension section of the telescopic layer; and the first extension sections of the telescopic layers of the first extension arm and the second extension arm are curved towards each other.

[0011] In addition to one or more of the features described herein, or as an alternative, further embodiments of the MEMS Fabry-Perot filter can include that the telescopic layer of the first extension arm and the second extension arm each has a middle section covered by the two first electrothermal layers.

[0012] In addition to one or more of the features described herein, or as an alternative, further embodiments of the MEMS Fabry-Perot filter can include that each of the drive frames includes two drive sub-frames, and the two drive sub-frames are symmetric 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 manufacturing a MEMS Fabry-Perot filter is provided, comprising: forming the first electrothermal layer, the first insulating layer, the resistance layer, the second insulating layer, the second electrothermal layer and another first electrothermal layer in order from bottom to top on the top surface of an SOI silicon wafer to form the driving unit; forming the first reflecting layer on the top surface of the SOI silicon wafer; forming a cavity 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 and the base silicon wafer to form 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 suspended under the support of the driving assembly; and the driving assembly is provided with the driving unit.

[0014] One of the above technical solutions has the following advantages or beneficial effects: in view of the existing technical deficiencies, the present application proposes an electrothermal driving MEMS Fabry-Perot filter in which the upper plate always moves parallel to the second reflecting layer, which can keep the first reflecting layer and the second reflecting layer always parallel, and by providing a driving assembly containing the driving unit, the moving range of the upper plate can be large, and the filtering efficiency and light utilization rate of the filter are improved. At the same time, the driving unit is formed by combining the expansion layer and at least one first electrothermal layer, and the electrothermal driving structure can realize the miniaturization of the entire filter, which is convenient for further simplifying the structure, reducing the overall volume and weight, improving 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 also compatible with the COMS (Complementary Metal Oxide Semiconductor) process.

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

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0017] Figure 1 is a perspective view of the MEMS Fabry-Perot filter provided by at least one embodiment of the present application;

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

[0019] Figure 3 Figure 1 is a plan view of a driving support provided by the present application; Figure 2 Figure 2 is a plan view of a driving support provided by the present application;

[0020] Figure 4 Figure 3 is a plan view of a driving arm provided by at least one embodiment of the present application;

[0021] Figure 5 Figure 4 is a sectional view of a second extension arm (before the driving arm is opened) provided by at least one embodiment of the present application;

[0022] Figure 6 Figure 5 is a front view of a driving arm (after being opened) provided by at least one embodiment of the present application;

[0023] Figure 7 Figure 6 is a process diagram of a method for manufacturing a MEMS Fabry-Perot filter provided by at least one embodiment of the present application.

[0024] In the figures, the reference signs are as follows:

[0025] 1: substrate silicon 2: buried oxide layer

[0026] 3: top silicon layer 4: first electrothermal layer

[0027] 5: resistive layer 6: second electrothermal layer

[0028] 7: another first electrothermal layer 8: first reflective layer

[0029] 9: base silicon wafer 10: second reflective layer

[0030] 60: planar electrode 31: upper plate

[0031] 41: driving sub-support 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 side of the upper plate 80: connected side of the support frame

[0036] 20: second extension section 30: intermediate section

[0037] 21: first extension section 500: F-P cavity

[0038] 100: center line 600: telescopic layer

[0039] 11: first insulating layer 12: second insulating layer DETAILED DESCRIPTION

[0040] Embodiments of the present application are described below in detail with reference to examples thereof shown in the attached drawings, wherein the same or similar components are denoted by the same or similar reference numerals throughout. The embodiments described below are examples for explaining the present application and are not intended to be limiting to the present application.

[0041] In addition, the terms "first", "second", etc. are used only for the purpose of description and should not be understood as indicating or implying relative importance or implying a specified number of the technical features indicated. Therefore, the features defined with "first", "second", etc. can explicitly or implicitly include one or more of the features.

[0042] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and therefore should not be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be understood as limiting the present application.

[0043] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting", "fixing", etc. should be understood in a broad sense, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0044] In addition, in the description of the present application, the meaning of "multiple" is two or more, unless otherwise explicitly specified and limited.

[0045] In Figures 1 to 7For example, a MEMS Fabry-Perot filter provided by the present application is described and introduced. The MEMS Fabry-Perot filter provided by the present application comprises a support frame, an upper plate 31, a first reflecting layer 8 and a second reflecting layer 10, which are all arranged in the support frame and always parallel to each other, so as to jointly define a Fabry-Perot resonant cavity 500; the first reflecting layer 8 is arranged on the upper plate 31; a driving assembly is connected between the upper plate 31 and the support frame, and the driving assembly is provided with a driving unit; the driving unit is formed by combination of a telescopic layer 600 and at least one first heating layer 4; the telescopic layer 600 comprises a second heating layer 6, a resistance layer 5, a first insulating layer 11 arranged between the resistance layer 5 and the second heating layer 6, and a second insulating layer 12 arranged on the side of the resistance layer 5 away from the second heating layer 6; the thermal expansion coefficient of the first heating layer 4 is less than the thermal expansion coefficient of the second heating layer 6; the at least one first heating layer 4 is arranged to be attached to the second heating layer 6 and / or the second insulating layer 12, so that after the electric field of the resistance layer 5 changes, the second heating layer 6 is elongated and drives the at least one first heating layer 4 to bend in the opposite direction of the side where the first heating layer 4 is located, or the second heating layer 6 is shortened and drives the at least one first heating layer 4 to bend towards the side where the first heating layer 4 is located, so as to drive the upper plate 31 to translate away from or towards the second reflecting layer 10 to change the size of the Fabry-Perot resonant cavity 500.

[0046] It should be explained that the thermal expansion coefficient refers to the change rate of the length or volume of an object when the temperature changes. For solid substances, the thermal expansion coefficient generally refers to the length change amount caused by unit temperature change under the condition of constant pressure. The material with high thermal expansion coefficient can expand or contract by a larger amount after the temperature rises.

[0047] It should be noted that the thermal expansion coefficient of the first heating layer 4 is less than the thermal expansion coefficient of the second heating layer 6, which can be understood as that, compared with the second heating layer 6, the length change amount of the first heating layer 4 is smaller during the process of temperature rise or fall.

[0048] For example, as shown in a specific embodiment, Figure 5 At this time, the second heating layer 6 will shrink after the resistance layer 5 is powered on and the temperature rises, and the thermal expansion coefficient of the second heating layer 6 is greater than the thermal expansion coefficient of the first heating layer 4, so that the second heating layer 6 expands at a faster rate when heated, causing the first heating layer 4 to deform in the form of the second extension arm 4112 shown below. Figure 6

[0049] Of course, as long as the upper plate 31 can always be parallel to the second reflecting layer 10 during translation, the arrangement and attachment mode of the first heating layer 4 and the second heating layer 6, and the expansion or contraction of the second heating layer 6 after temperature rise are not specifically limited.

[0050] ​The application provides an electrothermal driving MEMS Fabry-Perot filter, in which the upper plate 31 always moves parallel to the second reflecting layer 10, the first reflecting layer 8 and the second reflecting layer 10 are always parallel, the driving assembly containing the driving unit is arranged, the moving range of the upper plate 31 is large, and the filtering efficiency and the light utilization rate of the filter are improved. Meanwhile, the driving unit is formed by combining the telescopic layer 600 and at least one first electrothermal layer 4, the electrothermal driving structure can realize the miniaturization of the whole filter, the structure is further simplified, the overall volume and weight are reduced, the impact resistance and reliability of the device are improved, and the application has great development potential in the future. The application is the same as the conventional MEMS processing technology and is compatible with the COMS (complementary metal oxide semiconductor) technology.

[0051] It should be noted that the thermal expansion coefficient of the first electrothermal layer 4 is smaller than that of the second electrothermal layer 6, the first electrothermal layer 4 can be made of a low-expansion coefficient material, and the second electrothermal layer 6 can be made of a high-expansion coefficient material; the low-expansion coefficient material can be silicon oxide, silicon nitride and the like, and metal oxides such as aluminum oxide and titanium oxide. The high thermal expansion coefficient material can be Al, gold and the like, and alloy and the like. The heating resistor can be Pt, Ti and the like. The Bragg reflecting layer is a multi-film layer material, which is mainly composed of TiO2, Ta2O5, Nb2O5 or SiN thin film high refractive index material, and SiO2 and the like low refractive index material.

[0052] In an embodiment of the application, referring to Figure 1 , the driving assembly comprises at least two driving supports, the at least two driving supports are connected between the support frame and the upper plate 31 and are each provided with a driving unit, and at least one pair of driving supports are arranged on opposite sides of the upper plate 31; in this way, the driving supports are arranged on the opposite sides of the upper plate 31, so that the structural stability and high reliability of the upper plate 31 in the translation process can be ensured; of course, the driving assembly can also comprise an assembly for changing the electric field of the resistor layer 5, and the assembly is not described in detail because it is not the focus of the application.

[0053] In an embodiment of the application, referring to Figure 1 , the structures of the at least two driving supports are consistent, so that the filter can be conveniently processed and prepared.

[0054] In an embodiment of the application, referring to Figure 1 , the number of the driving supports is four, and the four driving supports are arranged in a central symmetry relative to the geometric center of the upper plate 31. As shown in Figure 1 , the structure can be understood as that the upper plate 31 is connected with the inner side of the support frame through the driving supports in the up, down, left and right four directions, the structure is stable and reliable, and is convenient for batch processing; as shown inFigure 1 It can be seen that the upper plate 31 and the support frame can be both rectangular and regular, thereby further facilitating the machining and manufacturing.

[0055] Further, the four groups of electrically heated driving supports can be distributed symmetrically around the F-P cavity 500, and the upper plate 31 of the four groups of electrically heated driving arms 411 and the geometric center of the F-P cavity 500 are on a vertical line. In the four groups of electrically heated driving supports, each group of driving supports can adopt two groups of driving arms 411 with completely symmetrical multi-film layer structures.

[0056] In an embodiment of the present application, please refer to Figure 2 Each driving support includes at least one driving sub-support 41, and the at least one driving sub-support 41 is connected between the support frame and the upper plate 31 and is provided with a driving unit. Figure 2 (a), Figure 2 (b) shows a case where the number of driving sub-supports 41 is two, Figure 2 (c) shows a case where the number of driving sub-supports 41 is four, Figure 2 (d) shows a case where the number of driving sub-supports 41 is three, and of course the number of driving sub-supports 41 can also be one or more than four. When the number of driving sub-supports 41 is set, it can be determined according to the specific structure of the driving sub-support 41, the size of the driving force actually required for the translation of the upper plate 31, the preparation cost and difficulty, and other factors, which are not uniquely limited here.

[0057] In an embodiment of the present application, please continue to refer to Figure 2 Each driving sub-support 41 includes a driving arm 411, a first connecting arm 412, and a second connecting arm 413, and the driving arm 411 is provided with a driving unit; 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 makes the driving arm 411 connected to the upper plate 31 and the support frame through the first connecting arm 412 and the second connecting arm 413, which is helpful for the structural design of the driving arm 411. The driving arm 411 can be provided in the structure shown in Figure 2 (d) (the two ends of this structure can be understood as the first connecting arm 412 and the second connecting arm 413), can also be provided in the structure shown in Figure 2 (a), Figure 2 (b), Figure 2 (c) and other structures capable of being opened (this structure can satisfy a larger deflection angle of the upper plate 31), and can also be provided in a structure other than the structure shown in Figure 3

[0058] In an embodiment of the present application, please refer to Figures 4 to 6 ​, the driving arm 411 is provided with a first extension arm 4111 and a second extension arm 4112, both of which have opposite connecting ends 1a and free ends 1b, the connecting end 1a of the first extension arm 4111 is connected with the connecting end 1a of the second extension arm 4112, the free end 1b of the first extension arm 4111 is connected with the first connecting arm 412, and the free end 1b of the second extension arm 4112 is connected with the second connecting arm 413; both the first extension arm 4111 and the second extension arm 4112 are configured as driving units and can be opened away from each other in opposite directions; it should be pointed out 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 realized by the design form of the driving units of the first extension arm 4111 and the second extension arm 4112, and from the above content, it can be known that the attachment position of the first electric heating layer 4 affects the bending direction of the driving unit, the attachment position 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. The structure can make the upper plate 31 have a larger translation amplitude, further making the filter of the application applied to a wider range of fields and scenes.

[0059] In an embodiment of the present application, please refer to Figure 3 , before being opened away from each other, the first extension arm 4111 and the second extension arm 4112 extend in the same plane, and the opposite directions are perpendicular to the same plane; this structure can further make the upper plate 31 have a larger translation amplitude, and at the same time, the structure is simple, easy to manufacture, and the translation process of the upper plate 31 is more stable and reliable.

[0060] In an embodiment of the present application, please refer to 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, which is simple and easy to realize, and the connection between the first extension arm 4111 and the second extension arm 4112 is smoothly transitioned, reducing fatigue stress and improving the service life of the driving arm 411, and the structure is stable and reliable.

[0061] In an embodiment of the present application, please refer to Figure 1 , the first connecting arms 412 of the driving sub-frames 41 of the same driving bracket are all connected to the middle part of the connected edge 50 of the upper plate 31, and the second connecting arms 413 are all connected to the middle part of the connected edge 80 of the support frame, which can make the first connecting arms 412 of the driving sub-frames 41 of the same driving bracket concentrate the driving force to be effectively and stably transmitted to the upper plate 31, so as to make it stably translate; on the other hand, it can ensure that the driving sub-frames 41 of the same driving bracket are more stable in posture when moving between the upper plate 31 and the support frame, and the overall structure is stable and reliable.

[0062] In one embodiment of the present application, please refer to Figure 6 Each second connecting arm 413 is connected to the support frame through a planar electrode 60.

[0063] In one embodiment of the present application, please refer to Figure 5 The first extension arm 4111 and the second extension arm 4112 are both formed by a combination of a telescopic layer 600 and two first electrothermal layers 4; the telescopic layer 600 of the first extension arm 4111 and the second extension arm 4112 both has a first extension section 21 close to the respective connecting end 1a and a second extension section 20 close to the respective free end 1b, the two first electrothermal layers 4 of the first extension arm 4111 are respectively attached to the opposite sides of the telescopic layer 600 and are respectively covered on the first extension section 21 and the second extension section 20 of the telescopic layer 600; the two first electrothermal layers 4 of the second extension arm 4112 are respectively attached to the opposite sides of the telescopic layer 600 and are respectively covered on the first extension section 21 and the second extension section 20 of the telescopic layer 600; the first extension section 21 of the telescopic layer 600 of the first extension arm 4111 and the second extension arm 4112 is curved towards each other, it is necessary to explain that curved towards each other means curved towards the direction of the other party. This structure not only ensures a large degree of translation of the upper plate 31, but also further reduces the stress of the first extension arm 4111 and the second extension arm 4112 at the connection, the structure is reasonable and stable, and easy to realize. For easy understanding, the multi-film layer driving arm 411 is similar to a sandwich structure composed of a material with low expansion coefficient, a heating resistance material, an upper and lower insulation layer material, and a material with high thermal expansion coefficient, as shown in Figure 6 .

[0064] In one embodiment of the present application, please continue to refer to Figure 3 The telescopic layer 600 of the first extension arm 4111 and the second extension arm 4112 both has a middle section 30 covered by the two first electrothermal layers 4. By setting this structure, the bending deformation critical point of the telescopic layer 600 of the first extension arm 4111 and the second extension arm 4112 can be better protected and transitioned, and the structural stability and service life of the first extension arm 4111 and the second extension arm 4112 are improved.

[0065] In one embodiment of the present application, please refer to Figure 1 Each driving bracket includes two driving sub-brackets 41, and the two driving sub-brackets 41 are a symmetrical structure with the center line 100 of the upper plate 31 as the axis of symmetry. The center line 100 of the upper plate 31 can be understood as the axis of symmetry of the upper plate 31, when the upper plate 31 is Figure 7The center line 100 can exist in two, if the upper plate 31 is a circle, the center line 100 can exist in several, at this time, the two driving sub-supports 41 can also be a symmetrical structure with the center line 100 of the circular upper plate 31 as the symmetrical axis. The symmetrical structure is easy to process and realize, and the two driving sub-supports 41 have better balance consistency in the process of applying driving force to the upper plate 31, which helps to realize the stable and reliable deflection process of the upper plate 31.

[0066] In another aspect, the application also provides a preparation method of the MEMS Fabry-Perot filter, which can specifically include: forming a first electrothermal layer 4, a first insulating layer 11, a resistance layer 5, a second insulating layer 12, a second electrothermal layer 6 and another first electrothermal layer 7 on the top surface of the SOI silicon wafer from bottom to top to form a driving unit; forming a first reflective layer 8 on the top surface of the SOI silicon wafer; forming a cavity 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 and the base silicon wafer to form a Fabry-Perot resonant cavity 500 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 the first reflective layer 8, and making the upper plate 31 suspended under the support of the driving assembly; the driving assembly is provided with the driving unit.

[0067] As a specific embodiment, please refer to Figure 7 The manufacturing method of the MEMS Fabry-Perot filter can adopt a silicon-based semiconductor preparation process, mainly including photolithography, sputtering, stripping, chemical vapor deposition, etching, bonding and the like. The preparation process flow is as shown in Figure 7 (a)-(m), and is specifically as follows:

[0068] Step 1: A six-inch silicon wafer on an insulating substrate (Silicon-On-Insulator, SOI) is used as a substrate to manufacture a front cavity of the F-P cavity MEMS with the upper plate 31. The surface of the silicon wafer is cleaned by using SCA cleaning process, as shown in Figure 7 (a); wherein the thickness of the substrate silicon 1 is about 300-600 μm, the thickness of the buried oxide layer 2 (SiO2) is about 0.5-2 μm, and the thickness of the top layer silicon 3 is about 10-60 μm; the substrate silicon 1, the buried oxide layer 2 and the top layer silicon 3 together constitute the SOI silicon wafer.

[0069] Step 2, growth of normal sequence SiO2 (first electrothermal layer 4). A layer of SiO2 is grown on the surface of a six-inch wafer (it should be noted that the SOI silicon wafer is simply referred to as a wafer herein, and the cross section thereof can not be limited to a circular shape) as the normal sequence SiO2 of the driving arm 411 by using a plasma enhanced chemical vapor deposition (PECVD) method, and the film thickness thereof is about 1 μm to 2 μm.

[0070] Step 3, first photoetching, using a positive photoresist AZ5214; a series of photoetching processes such as coating, photoetching, and developing are performed on the SOI substrate on which the SiO2 is grown, so as to expose the places where the SiO2 needs to be removed and cover the places where the SiO2 does not need to be removed with the photoresist.

[0071] Step 4, etching of the normal sequence SiO2 of the driving arm 411, using a wet etching process; the wafer after photoetching is etched by using a buffered oxide etch (BOE) solution, so as to remove the SiO2 not covered by the photoresist, and a normal sequence SiO2 pattern layer (first electrothermal layer 4) is obtained after etching, as shown in FIG. 2 (b). Figure 7

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

[0073] Step 6, second photoetching, using AZ5214 as a reverse photoresist through two times of exposure, the first time of exposure needs to use a photoetching mask, and the second time of exposure is performed without a mask; meanwhile, a negative photoresist can also be used for one-time mask exposure.

[0074] Step 7, preparation of the heating resistor (resistor layer 5) of the driving arm 411 by using a magnetron sputtering method, and Pt, Ti, or other sputtering targets can be used; a Pt or Ti film is sputtered on the surface of the wafer after photoetching as the heating resistor of the electrothermal driving arm 411, and the thickness thereof is about 0.05 μm to 0.15 μm.

[0075] Step 8, Pt stripping process, the six-inch wafer is placed in acetone for soaking, ultrasonic cleaning, and then sequentially cleaned with anhydrous ethanol and deionized water, and then spin-dried; the resistor layer 5 of the electrothermal driving arm 411 is formed, and after stripping, as shown in FIG. 2 (c). Figure 7

[0076] Step 9, growth of the second insulating silicon oxide (second insulating layer 12), a thin layer of SiO2 is grown on the surface of the wafer as an insulating layer for covering the heating resistor by using a plasma enhanced chemical vapor deposition (PECVD) method, and the film thickness thereof is about 0.01 μm to 0.1 μm.​​

[0077] Step 10, third photoetching, AZ5214 is used for reverse photoresist through twice exposure, the first exposure needs to use photoetching mask, and the second exposure is carried out without mask exposure; meanwhile, negative photoresist can also be used to carry out once mask exposure.

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

[0079] Step 11, Al stripping process, the wafer is placed in acetone for soaking, ultrasonic, and then sequentially cleaned with anhydrous ethanol and deionized water, and spin-drying treatment; the Al and lead (second heating layer 6) of the electric heating driving are formed, and after stripping, as shown in Figure 7 (d).

[0080] Step 12, reverse SiO2 (another first heating layer 7) growth, PECVD process is used to grow SiO2 on the surface of the wafer as reverse SiO2 of the electric heating driving arm 411, and the thickness is about 1 μm-2 μm.

[0081] Step 13, fourth photoetching, through photoetching process, the photoresist in the place where the reverse SiO2 needs to be removed is removed, and the photoresist covers the place where the SiO2 needs to be left.

[0082] Step 14, reverse SiO2 is etched by dry etching process, the SiO2 not covered by the photoresist is etched, and after etching, the reverse SiO2 layer (another first heating layer 7) is obtained, as shown in Figure 7 (e).

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

[0084] Step 16, front cavity Si etching, dry etching process is used to etch the Si not covered by the photoresist, and after etching, as shown in Figure 7 (f).

[0085] Step 17, fifth photoetching, through photoetching process, the photoresist in the place where the top silicon 3 needs to be removed is removed, and the rest is covered by the photoresist.

[0086] Step 18, front cavity Bragg reflection surface (first reflection layer 8) deposition, using magnetron sputtering, alternating deposition of high refractive index and low refractive index material, wherein the high refractive index uses magnetron sputtering TiO2 target, or Ta2O5 target, or Nb2O5 target, or SiN target to prepare TiO2 film, or Ta2O5 film, or Nb2O5 film, or SiN film; the low refractive index material uses PECVD to deposit SiO2 film.

[0087] Step 18, front cavity Bragg reflection surface (first reflection layer 8) stripping, placing the wafer in acetone for soaking, ultrasonic, and then sequentially cleaning with anhydrous ethanol and deionized water, and spin-drying treatment; forming the first reflection layer 8, after stripping as shown in Figure 7 (g).

[0088] Step 19, sixth lithography, performing the sixth lithography process on the back surface of the SOI wafer to define the area to be etched for the F-P cavity 500.

[0089] Step 20, using DRIE deep silicon etching process, etching the wafer from the back surface to etch the substrate silicon 1 to the middle SiO2 layer; then, using SiO2 etching equipment, etching the middle SiO2 of the wafer, after etching as shown in Figure 7 (h).

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

[0091] Step 22, seventh lithography, defining the position of the F-P cavity back cavity Bragg reflection layer (second reflection layer 10) through the lithography process, removing the photoresist where the Bragg reflection layer (second reflection layer 10) is needed, and covering the rest with photoresist.

[0092] Step 23, back cavity Bragg reflection surface (second reflection layer 10) deposition, using magnetron sputtering, alternating deposition of high refractive index and low refractive index material, wherein the high refractive index uses magnetron sputtering TiO2 target, or Ta2O5 target, or Nb2O5 target, or SiN target to prepare TiO2 film, or Ta2O5 film, or Nb2O5 film, or SiN film; the low refractive index material uses PECVD to deposit SiO2 film.

[0093] Step 24, back cavity surface Bragg reflection surface (second reflection layer 10) stripping, the wafer is placed in acetone for soaking, ultrasonic, and then sequentially cleaned with anhydrous ethanol and deionized water, and spin-drying treatment; the second reflection layer 10 is formed, and after stripping, as shown in Figure 7 (j) is 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 integrated cavity, as shown in ​ (k) is shown.

[0095] Step 26, wafer front surface release, etching the front surface of the wafer; the unnecessary top layer of silicon 3 is etched away, at this time, the front cavity surface (upper plate 31) with the Bragg reflection layer will be in a suspended state under the support of the electric heating type driving arm 411, as shown in ​ (m) is shown.

[0096] Step 27, scribing, the prepared wafer is cut into single core particles by laser scribing.

[0097] Step 28, pressure welding, packaging.

[0098] Step 29, chip testing.

[0099] It can be seen that the specific electric heating driven F-P cavity MEMS wavelength tunable filter embodiment proposed in the present application can be divided into a back 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 F-P cavity 500. The front cavity surface of the F-P cavity 500 is the upper plate 31 with a hollow area in the middle, and four groups of electric heating driving arms 411 are connected around it. The four groups of electric heating driving arms 411 connect the upper plate 31 and the side surface of the F-P cavity 500, constituting a movable upper plate 31, which can move up and down under the driving of electric heating, thereby changing the size of the F-P cavity 500.

[0100] Obviously, the above embodiments of the present application are only examples for clear illustration of the present application, and are not a limitation on the embodiments of the present application. For ordinary skilled persons in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to exhaust all the embodiments. Any modification, equivalent replacement and improvement made within the spirit and principles of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A MEMS Fabry-Perot filter, characterized in that, The application relates to a support frame, an upper pole plate, a first reflecting layer and a second reflecting layer, which are arranged in the support frame and are parallel to each other to jointly define a Fabry-Perot resonant cavity, the first reflecting layer is arranged on the upper pole plate, and the upper pole plate can move while being parallel to the second reflecting layer. A driving assembly is connected between the upper pole plate and the support 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 electrothermal layer, the telescopic layer comprises a second electrothermal layer, a resistance layer, a first insulating layer arranged between the resistance layer and the second electrothermal layer, and a second insulating layer arranged on the side of the resistance layer away from the second electrothermal layer. The coefficient of thermal expansion of the first electrothermal layer is smaller than that of the second electrothermal layer, and the at least one first electrothermal layer is arranged on the second electrothermal layer and / or the second insulating layer to drive the second electrothermal layer to be elongated and bent in the direction opposite to the side where the first electrothermal layer is located or to be shortened and bent in the direction of the side where the first electrothermal layer is located after the electric field of the resistance layer changes, so that the upper pole plate is driven to move away from or towards the second reflecting layer to change the size of the Fabry-Perot resonant cavity. The driving assembly comprises at least two driving supports which are connected between the support frame and the upper pole plate and are each provided with the driving unit, and at least one pair of the driving supports are arranged on opposite sides of the upper pole plate. The structures of the at least two driving supports are consistent, and / or the number of the driving supports is four, and the four driving supports are arranged in a central symmetry relative to the geometric center of the upper pole plate. Each of the driving supports comprises at least one driving sub-support which is connected between the support frame and the upper pole plate and is provided with the driving unit.

2. The MEMS Fabry-Perot filter of claim 1, wherein, Each of the driving sub-supports comprises 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 pole plate through the first connecting arm and is connected to the support frame through the second connecting arm.

3. The MEMS Fabry-Perot filter of claim 2, wherein, 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 have opposite connecting ends and free ends, the connecting end of the first extension arm is connected to the connecting end of the second extension arm, 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 arranged to be away from each other in opposite directions.

4. The MEMS Fabry-Perot filter according to claim 2 or 3, characterized in that, Before being away from each other, the first extension arm and the second extension arm extend in the same plane, and the opposite directions are perpendicular to the same plane.

5. The MEMS Fabry-Perot filter of claim 4, wherein, The first extension arm and the second extension arm of the driving arm are arranged to be combined into a U shape.

6. The MEMS Fabry-Perot filter of claim 5, wherein, ​ 7. The MEMS Fabry-Perot filter of claim 6, wherein, ​ ​ And / or, the first connecting arms of the driving sub-supports of the same driving support are connected to the middle of the connected edges of the upper plate, and the second connecting arms are connected to the middle of the connected edges of the support frame; And / or, each of the second connecting arms is connected to the support frame through a planar electrode; And / or, the first extension arm and the second extension arm are formed by a combination of one telescopic layer and two first electrothermal layers; the telescopic layer of the first extension arm and the telescopic layer of the second extension arm each have a first extension section close to the respective connecting end and a second extension section close to the respective free end, the two first electrothermal layers of the first extension arm are respectively attached to the opposite sides of the telescopic layer of the first extension arm and are respectively covered on the first extension section and the second extension section of the telescopic layer, the two first electrothermal layers of the second extension arm are respectively attached to the opposite sides of the telescopic layer of the second extension arm and are respectively covered on the first extension section and the second extension section of the telescopic layer, and the first extension sections of the telescopic layers of the first extension arm and the second extension arm are curved towards each other.

8. The MEMS Fabry-Perot filter of claim 7, wherein, The telescopic layer of the first extension arm and the telescopic layer of the second extension arm each have a middle section covered by the two first electrothermal layers.

9. The MEMS Fabry-Perot filter of claim 4, wherein, Each of the driving supports includes two driving sub-supports, and the two driving sub-supports are symmetric structures with the center line of the upper plate as the axis of symmetry.

10. A method for manufacturing a MEMS Fabry-Perot filter according to any one of claims 1-9, comprising: forming the first electrothermal layer, the first insulating layer, the resistance layer, the second insulating layer, the second electrothermal layer, and another first electrothermal layer on the top surface of the SOI silicon wafer from bottom to top to form the driving unit; forming the first reflective layer on the top surface of the SOI silicon wafer; forming a cavity 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 base silicon wafer to form 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 plate provided with the first reflective layer, and suspending the upper plate under the support of the driving assembly; the driving assembly is provided with the driving unit.

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