WO2019144370A1 - Mems压电扬声器及其制备方法 - Google Patents

Mems压电扬声器及其制备方法 Download PDF

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Publication number
WO2019144370A1
WO2019144370A1 PCT/CN2018/074277 CN2018074277W WO2019144370A1 WO 2019144370 A1 WO2019144370 A1 WO 2019144370A1 CN 2018074277 W CN2018074277 W CN 2018074277W WO 2019144370 A1 WO2019144370 A1 WO 2019144370A1
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layer
piezoelectric
substrate
bottom electrode
structural
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PCT/CN2018/074277
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English (en)
French (fr)
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刘端
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刘端
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Priority to PCT/CN2018/074277 priority Critical patent/WO2019144370A1/zh
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R17/00—Piezoelectric transducers; Electrostrictive transducers

Definitions

  • the present disclosure relates to the field of microelectronic mechanical system technologies, and in particular, to a MEMS piezoelectric speaker and a method of fabricating the same.
  • MEMS devices are new devices fabricated using microelectronics and micromachining technology. Compared with traditional devices, it has the characteristics of small size, light weight, low cost, low power consumption, high reliability, suitable for mass production, easy integration and intelligentization.
  • MEMS speakers have the advantages of small size and low power. MEMS speakers are classified according to their working principles, including MEMS electromagnetic speakers and piezoelectric speakers. MEMS piezoelectric speakers have the advantages of low power consumption and simple processing. However, low sensitivity is one of the main reasons that affect the industrialization of MEMS speakers. Promoting the industrialization of MEMS piezoelectric speakers means improving the sensitivity of MEMS piezoelectric speakers. Therefore, improving the sensitivity of MEMS piezoelectric speakers is an urgent technical problem in the industrialization process of MEMS piezoelectric speakers.
  • the present disclosure provides a MEMS piezoelectric speaker and a method of fabricating the same to improve the sensitivity of a MEMS piezoelectric speaker.
  • the present disclosure provides a MEMS piezoelectric speaker comprising: a substrate having a central region as a hollow region; an organic diaphragm layer positioned above the hollow region of the substrate, spaced from the substrate; and a structural beam a spoke-like distribution formed on the substrate to support the organic vibrating membrane.
  • the structural beam comprises, in order from bottom to top, a composite dielectric layer and a piezoelectric unit, wherein the gap between the structural beams is a structural groove;
  • the structural beam and the organic diaphragm layer constitute a piezoelectric composite diaphragm.
  • the piezoelectric unit includes, in order from bottom to top, a bottom electrode, a piezoelectric layer, and a top electrode; or the piezoelectric unit includes, in order from bottom to top, a bottom electrode, a piezoelectric layer, and The top electrode has at least one insulating spacer between the bottom electrode and the piezoelectric layer or the top electrode and the piezoelectric layer.
  • the piezoelectric layer is made of one or more of the following materials: zinc oxide, aluminum nitride, lead zirconate titanate, relaxed piezoelectric material, perovskite piezoelectric
  • the material, or the organic piezoelectric material; and/or the bottom electrode and the top electrode are: a metal single layer film, a metal multilayer film, a non-metal conductive film, or a combination of a metal and a non-metal conductive film.
  • the piezoelectric layer has a thickness of between 0.01 ⁇ m and 60 ⁇ m; and/or the bottom electrode and the top electrode have a thickness of between 0.01 ⁇ m and 5 ⁇ m.
  • the material of the organic vibrating membrane layer is one of the following materials: polyimide, parylene, polyurethane, or other organic film; and/or thickness of the organic vibrating membrane layer Between 0.01 ⁇ m and 30 ⁇ m; and/or the composite dielectric layer includes, in order from bottom to top, a first silicon nitride layer, a silicon oxide layer, and a second silicon nitride layer; a first silicon nitride layer and a silicon oxide layer; And the thickness of the second silicon nitride layer is between 0.01 ⁇ m and 30 ⁇ m, respectively; or the composite dielectric layer comprises, in order from bottom to top, a first silicon oxide layer, a silicon nitride layer, and a second silicon dioxide layer; and/ Or the thickness of the first silicon oxide layer, the silicon nitride layer and the second silicon oxide layer are respectively between 0.01 ⁇ m and 30 ⁇ m; or the composite dielectric layer comprises, in order from bottom to top, a silicon
  • the silicon layer, the oxide layer; and/or the thickness of the silicon layer and the oxide layer are respectively between 0.01 ⁇ m and 30 ⁇ m; or the composite dielectric layer comprises a silicon nitride layer, a silicon oxide layer, polysilicon, phosphosilicate glass, boron One of silicon glass or a single combination of two or more of them
  • the layer or multilayer structure, and/or the thickness of the silicon nitride layer, the silicon oxide layer, the polysilicon, the phosphosilicate glass, and the borosilicate glass are respectively between 0.01 ⁇ m and 30 ⁇ m.
  • the MEMS piezoelectric speaker further includes: a mask layer for dry or wet body etching on the back side of the substrate; and an insulating isolation layer formed on the bottom electrode Located around the piezoelectric layer, supporting the top electrode, and isolating the bottom electrode and the top electrode; wherein the composite dielectric layer, the bottom electrode, the insulating isolation layer and the top electrode above the insulating isolation layer form an outer frame, the outer frame and the structural beam Achieve support for organic diaphragms.
  • an opening is included in the insulating spacer such that the bottom electrode is exposed, the opening being a bottom electrode pad.
  • the number of structural slots is between 2 and 30.
  • the present disclosure further provides a method for fabricating a MEMS piezoelectric speaker, the method comprising: fabricating a structural beam having a spoke-like distribution on a front surface of a substrate, the structural beam comprising: from bottom to top: a composite dielectric layer and a piezoelectric unit, wherein a gap between the structural beams is a structural groove; an organic vibration film layer is formed over the structural beam; and the substrate is etched such that a central region of the substrate facing the organic vibration film layer is a hollow region .
  • fabricating the structural beam on the front side of the substrate includes: forming a composite dielectric layer on the front surface of the substrate; sequentially forming a patterned bottom electrode and a piezoelectric layer on the composite dielectric layer, the patterned bottom electrode The intermediate portion is distributed in a spoke shape, and a peripheral edge region is formed around the periphery.
  • the patterned piezoelectric layer is located above the middle portion of the bottom electrode, and has the same shape as the middle portion of the bottom electrode, and the size can be adjusted; around the piezoelectric layer Forming an insulating isolation layer; forming a patterned top electrode over the piezoelectric layer and the insulating isolation layer, the patterned top electrode being spoke-shaped, the patterned top electrode and the patterned bottom and piezoelectric layers
  • the shape is the same, the size can be adjusted; and the composite dielectric layer under the gap between the spokes is etched to form a structural groove, the unetched region forms a spoke-shaped structural beam; an organic vibration film layer is formed above the structural beam,
  • the organic diaphragm layer covers the entire hollow area or only covers a partial area above the structural groove.
  • etching the substrate such that the central region of the substrate facing the organic vibrating film layer is a hollow region comprising: filling the filling sacrificial layer in the structural groove, depositing an organic vibrating film on the structural beam and filling the sacrificial layer, and depositing on the back surface for deposition a dry or wet body etching mask layer, a patterned mask layer, performing body etching such that a central region of the substrate facing the organic vibrating film layer is a hollow region, and the sacrificial layer is removed;
  • the mask layer of the dry or wet body etching is retained or removed in the final device; a top end of the piezoelectric unit is further included, and an opening is formed on the insulating isolation layer to expose the bottom electrode
  • the opening is a bottom electrode pressure welding hole.
  • the MEMS piezoelectric speaker provided by the present disclosure and the preparation method thereof have the following beneficial effects:
  • the structural beam includes a piezoelectric unit, and the gap between the structural beams is a structural groove, and the structural groove makes The stress of the diaphragm is released, and the piezoelectric unit on the structural beam is easily subjected to electrical load, and the piezoelectric composite diaphragm is likely to generate a large amplitude of vibration, thereby improving the sensitivity of the piezoelectric speaker;
  • 1A-1D are various views of a MEMS piezoelectric speaker having four structural slots and four structural beams, in accordance with an embodiment of the present disclosure.
  • 1A is a cross-sectional view of a MEMS piezoelectric speaker taken along line A-A, in accordance with an embodiment of the present disclosure.
  • FIG. 1B is a cross-sectional view of the MEMS piezoelectric speaker taken along line B-B, according to an embodiment of the present disclosure.
  • FIG. 1C is a top plan view of a MEMS piezoelectric speaker shown in accordance with an embodiment of the present disclosure.
  • FIG. 1D is a bottom view of a MEMS piezoelectric speaker shown in accordance with an embodiment of the present disclosure.
  • FIG. 2 is a flow chart of a method of fabricating a MEMS piezoelectric speaker according to an embodiment of the present disclosure.
  • 3 to 15 are schematic structural views corresponding to respective steps of preparing a MEMS piezoelectric speaker.
  • Fig. 3 is a schematic cross-sectional view taken along the A-A plane after the oxide layer is grown on the substrate.
  • FIG. 4 is a schematic cross-sectional view taken along the A-A plane after the composite dielectric layer is grown on the front side of the substrate.
  • Fig. 5A is a schematic cross-sectional view taken along the A-A plane after the bottom electrode is grown on the composite dielectric layer.
  • Figure 5B is a top plan view of the bottom electrode after growth on the composite dielectric layer.
  • Fig. 6A is a schematic cross-sectional view taken along the A-A plane after the piezoelectric layer is grown on the bottom electrode.
  • Fig. 6B is a plan view of the piezoelectric layer grown on the bottom electrode.
  • Fig. 7A is a schematic cross-sectional view taken along the A-A plane after the insulating spacer is grown around the piezoelectric layer.
  • Fig. 7B is a plan view of the insulating spacer layer grown around the piezoelectric layer.
  • Fig. 8A is a schematic cross-sectional view taken along line A-A after forming a top electrode over the piezoelectric layer and the insulating spacer.
  • Fig. 8B is a plan view showing the formation of a top electrode over the piezoelectric layer and the insulating spacer.
  • FIG. 9A is a schematic cross-sectional view taken along line B-B of the composite dielectric layer after forming the structural trench.
  • FIG. 9B is a plan view of the etched composite dielectric layer forming a structural trench.
  • Fig. 10A is a schematic cross-sectional view taken along line B-B after forming a sacrificial layer in the structure trench.
  • Fig. 10B is a plan view showing the formation of a filling sacrificial layer in the structure trench.
  • Fig. 11A is a schematic cross-sectional view taken along line B-B of the organic vibrating film layer formed above the filling sacrificial layer.
  • FIG. 11B is a plan view of the organic vibration film layer formed above the filling sacrificial layer.
  • FIG. 12 is a schematic cross-sectional view taken along line B-B after etching the back oxide layer to form a mask layer.
  • Fig. 13 is a schematic cross-sectional view taken along line B-B of the base etching.
  • Figure 14 is a cross-sectional view of the MEMS piezoelectric speaker taken along the B-B plane after the sacrificial layer is etched.
  • Figure 15 is a cross-sectional view of the MEMS piezoelectric speaker taken along the A-A plane after the sacrificial layer is etched.
  • low sensitivity is one of the main reasons that affect the industrialization of MEMS loudspeakers.
  • the high stress of the diaphragm and the low vibration amplitude are the direct causes of low sensitivity.
  • the vibration amplitude and radiated sound pressure of the MEMS speaker are increased, thereby increasing the sensitivity and contributing to the industrialization of the MEMS piezoelectric speaker.
  • the present disclosure provides a MEMS piezoelectric speaker and a method for fabricating the same.
  • the structural beam is supported under the diaphragm of the MEMS piezoelectric speaker, and the structural beam is distributed according to the spoke shape, and the structural groove is a structural groove between the structural beams.
  • the groove causes the stress of the diaphragm located above it to be released, and the piezoelectric unit on the structural beam is easily subjected to an electric load, and the piezoelectric composite diaphragm is likely to generate a large amplitude of vibration, thereby improving the sensitivity of the piezoelectric speaker.
  • back side of the substrate corresponds to the lower surface of the substrate in the drawing
  • front side of the substrate corresponds to the upper surface of the substrate
  • numerical range “between” includes the end point value
  • a MEMS piezoelectric speaker is provided.
  • 1A-1D are various views of a MEMS piezoelectric speaker having four structural slots and four structural beams, in accordance with an embodiment of the present disclosure.
  • 1A is a cross-sectional view of the MEMS piezoelectric speaker taken along the AA plane according to an embodiment of the present disclosure
  • FIG. 1B is a cross-sectional view of the MEMS piezoelectric speaker along the BB plane according to an embodiment of the present disclosure.
  • 1C is a top view of a MEMS piezoelectric speaker according to an embodiment of the present disclosure
  • FIG. 1D is a bottom view of the MEMS piezoelectric speaker according to an embodiment of the present disclosure.
  • the MEMS piezoelectric speaker of the present disclosure includes: a substrate 10 having a central region as a hollow region; a mask layer 60 on the back surface of the substrate 10; and an organic vibrating film layer 50 on the substrate 10 Above the hollow region, there is a distance from the substrate 10; and the structural beam is distributed in a spoke shape, formed on the substrate 10, and supports the organic vibration film 50, which comprises the composite dielectric layer 20 and the piezoelectric layer from bottom to top.
  • the unit 30, the gap portion between the structural beams is a structural groove 70; wherein the structural beam and the organic diaphragm layer 50 constitute a piezoelectric composite diaphragm.
  • the substrate 10 is a silicon substrate.
  • the substrate 10 of the present disclosure is not limited to the example of the embodiment, and may be an SOI substrate or other substrate.
  • the selection of the substrate 10 is performed according to actual needs.
  • the composite dielectric layer 20 includes, in order from bottom to top, a first silicon nitride layer 21, a silicon oxide layer 22, and a second silicon nitride layer 23, wherein the silicon oxide layer is preferably A silicon oxide layer grown under low temperature conditions is used.
  • the thicknesses of the first silicon nitride layer 21, the silicon oxide layer 22, and the second silicon nitride layer 23 are each between 0.01 ⁇ m and 30 ⁇ m.
  • the number of layers of the composite dielectric layer 20 of the present disclosure is not limited, and the material of each layer is not limited to the above embodiment.
  • the number of layers of the composite dielectric layer and the materials of the layers can be selected according to actual needs.
  • the composite dielectric layer 20 includes, in order from bottom to top, a first silicon oxide layer, a silicon nitride layer, and a second silicon oxide layer.
  • the first silicon oxide layer, the silicon nitride layer and the second silicon oxide layer have a thickness of between 0.01 ⁇ m and 30 ⁇ m, respectively.
  • the composite dielectric layer includes, in order from bottom to top, a silicon layer, an oxide layer or an oxide layer, a silicon layer, and an oxide layer.
  • the thickness of the silicon layer and the oxide layer are respectively between 0.01 ⁇ m and 30 ⁇ m.
  • the composite dielectric layer is a single layer or a multilayer structure including one of a silicon nitride layer, a silicon oxide layer, polysilicon, phosphosilicate glass, borosilicate glass, or any two of them.
  • the thickness of the silicon nitride layer, the silicon oxide layer, the polycrystalline silicon, the phosphosilicate glass, and the borosilicate glass is between 0.01 ⁇ m and 30 ⁇ m, respectively.
  • the piezoelectric unit 30 includes, in order from bottom to top, a bottom electrode 31, a piezoelectric layer 32, and a top electrode 33.
  • an insulating isolation layer may also be included between the electrodes of the piezoelectric unit and the piezoelectric layer.
  • the bottom electrode 31 and the top electrode 32 are a metal single layer film, a metal multilayer film, a non-metal conductive film, or a combination of a metal and a non-metal conductive film.
  • the material of the piezoelectric layer 32 is optional but not limited to one or more of the following materials: zinc oxide, aluminum nitride, lead zirconate titanate, relaxed piezoelectric material, perovskite type pressure An electrical material or an organic piezoelectric material; the piezoelectric layer has a thickness of between 0.01 ⁇ m and 60 ⁇ m.
  • the material of the bottom electrode 31 and the top electrode 33 may be selected from, but not limited to, one or a combination of the following materials: aluminum, copper, gold, platinum, molybdenum, chromium, titanium, lanthanum nickelate (LNO), and other metal or non-metal conductive films.
  • the thickness is between 0.01 ⁇ m and 5 ⁇ m.
  • the bottom electrode 31 and the top electrode 33 may also be an aluminum, a gold/chromium composite layer, or a platinum/titanium composite layer, and when the adhesion layer of the bottom electrode or the top electrode is a chromium layer, a titanium layer, or another conductive film layer, The thickness is between 0.01 ⁇ m and 1 ⁇ m.
  • the thickness of the aluminum electrode is between 0.01 ⁇ m and 5 ⁇ m
  • the thickness of the chromium layer or the titanium layer is between 0.01 ⁇ m and 1 ⁇ m
  • the thickness of the gold layer or the platinum layer is between 0.05 ⁇ m and 5 ⁇ m.
  • the structures and materials of the piezoelectric layer, the bottom electrode, and the top electrode exemplified in the embodiments are described by way of example only, and other novel materials and structures capable of functioning as a piezoelectric function and an electrode function are in this embodiment. Within the protection range of the disclosed piezoelectric unit.
  • the bottom electrode 31 has a patterned shape, and the intermediate portion is distributed in a spoke shape, and an edge region continuous therewith is formed around the periphery, as shown in FIG. 5B.
  • the piezoelectric layer 32 covers the intermediate portion of the bottom electrode 31 and also has a spoke-like distribution, as shown in Fig. 6B.
  • the top electrode 33 has a patterned shape overlying the piezoelectric layer 32 and beyond the periphery of the piezoelectric layer 32, that is, beyond the intermediate portion of the bottom electrode 31, for facilitating the between the top electrode 33 and the bottom electrode 31.
  • the pattern of the top electrode 33 is set to a shape as shown in FIG. 8B, and a lead end is provided on the pattern of the top electrode 33. It should be noted that the size of the bottom electrode, the piezoelectric layer, and the top electrode can be adaptively adjusted.
  • the MEMS piezoelectric speaker further includes an insulating isolation layer 40 formed on the bottom electrode 31 around the piezoelectric layer 32 to support the top electrode 33, as shown in FIGS. 1A and 1B. And separating the bottom electrode 31 and the top electrode 33; the lead end of the top electrode 33 is located on the insulating isolation layer 40; the composite dielectric layer 30, the bottom electrode 31, the insulating isolation layer 40 and the partial top electrode 33 constitute an outer frame, and the structure The beams collectively support the organic diaphragm 50.
  • the function of the insulating isolation layer is to realize the isolation between the bottom electrode and the top electrode and the support of the top electrode, and the height, the range of the surface of the bottom electrode, and the material are not limited, as long as the above functions can be achieved.
  • the MEMS piezoelectric speaker may not include an insulating isolation layer, and the original piezoelectric layer pattern is changed so as not to cover only the intermediate portion of the bottom electrode, and also in the edge region of the bottom electrode.
  • the piezoelectric layer is deposited such that the piezoelectric layer located at the edge region of the bottom electrode functions as an insulating spacer.
  • the material of the insulating spacer 40 may be selected from, but not limited to, one of the following materials: silicon oxide, silicon nitride, polyimide, parylene, polyurethane, or piezoelectric material, and the like.
  • the material of the organic vibrating film layer 50 is optional but not limited to one of the following materials: polyimide, parylene, polyurethane, or other organic film; the thickness of the organic vibrating film layer 50 is between Between 0.01 ⁇ m and 10 ⁇ m.
  • the shape of the organic vibrating membrane layer 50 is circular, and the shape of the hollow region in the central portion of the base 10 is also circular, and the two correspond to each other.
  • the hollow region of the central region of the substrate may have a square shape or other shape, and may be adaptively modified or adjusted according to the actual needs of the speaker. Accordingly, the shape of the organic diaphragm layer is the same as that of the hollow region. It is also possible to carry out adaptive modification or adjustment according to actual needs, and the speaker including the hollow region of each shape and the organic vibration film layer is within the protection scope of the present disclosure.
  • the thickness of the mask layer 60 is between 0.01 ⁇ m and 20 ⁇ m.
  • the structural beams are distributed in a spoke shape, and the number of corresponding structural grooves is between 2 and 30. In this embodiment, the number of structural grooves is four. The portion of the center of the spoke helps to enhance the strength of the support.
  • a bottom electrode pressing hole 41 is provided in the device of the MEMS piezoelectric speaker. Referring to FIGS. 1A and 1C, an opening is formed in the insulating isolation layer 40 such that the bottom electrode 31 is exposed. The opening is a bottom electrode bonding hole 41 for facilitating the device to perform electricity between the top electrode 33 and the bottom electrode 31. Sexual connection.
  • a method of fabricating a MEMS piezoelectric speaker is provided.
  • FIG. 2 is a flow chart of a method of fabricating a MEMS piezoelectric speaker according to an embodiment of the present disclosure.
  • 3 to 15 are schematic structural views corresponding to respective steps of preparing a MEMS piezoelectric speaker.
  • a method for manufacturing a MEMS piezoelectric speaker of the present disclosure includes:
  • Step S202 forming a mask layer on the back surface of the substrate
  • the oxide layer is used as the mask layer 60 as an example.
  • the mask layer of the present disclosure may also be other mask layers, and is not limited thereto.
  • the step S202 comprises: depositing an oxide layer on the upper and lower surfaces of the substrate, and then removing the oxide layer on the upper surface to obtain a substrate having an oxide layer on the back surface.
  • Fig. 3 is a schematic cross-sectional view taken along the A-A plane after the oxide layer is grown on the substrate.
  • the first silicon nitride layer 21, the silicon oxide layer 22, and the second silicon nitride layer 23 are selected, and the substrate 10 is determined to be a silicon material.
  • the base silicon is cleaned by standard cleaning method, boiled and cleaned with an acidic cleaning solution and an alkaline cleaning solution, and washed with deionized water, and finally dried with nitrogen; then, using a thermal oxidation furnace in the base silicon 10
  • an oxide layer is deposited as a mask layer 60.
  • a photoresist is coated on the mask layer 60 on the back side of the base silicon, and the front mask layer 60 is removed by a wet process, and finally removed. The photoresist on the mask layer 60 on the back side.
  • the substrate 10 of the present disclosure is not limited to the examples of the embodiments, and may be an SOI substrate or other substrate.
  • the matching of the substrate 10 and the composite dielectric layer 20 is performed according to the film structure of the composite dielectric layer 20 and the bonding state between it and the substrate 10, the ease of preparation, and the like.
  • the thickness of the mask layer 60 is 0.2 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 1.5 ⁇ m, 3 ⁇ m, or 3.5 ⁇ m, and the like, respectively.
  • Step S204 forming a composite dielectric layer on the upper surface of the substrate
  • FIG. 4 is a schematic cross-sectional view taken along the A-A plane after the composite dielectric layer is grown on the front side of the substrate.
  • a first silicon nitride layer 21, a silicon oxide layer 22, and a second silicon nitride layer 23 are sequentially deposited on the front surface of the base silicon by a plasma chemical vapor deposition (PECVD) method to form a composite dielectric layer 20, Among them, the silicon oxide layer 22 is preferably grown under low temperature conditions.
  • PECVD plasma chemical vapor deposition
  • the materials of the composite dielectric layer of other embodiments are also sequentially deposited according to a thin film deposition technique such as PECVD, which is a conventional preparation process and will not be described herein.
  • the thicknesses of the first silicon nitride layer 21, the silicon oxide layer 22, and the second silicon nitride layer 23 are respectively between 0.01 ⁇ m and 10 ⁇ m.
  • the first silicon nitride layer 21 and the second silicon nitride layer 23 each have a thickness of 0.5 ⁇ m, and the low temperature prepared silicon oxide layer 22 has a thickness of 0.2 ⁇ m; or the first silicon nitride layer 21 and the first The thickness of the silicon nitride layer 23 is 1 ⁇ m, and the thickness of the silicon oxide layer 22 prepared at a low temperature is 0.5 ⁇ m; or the first silicon nitride layer 21, the second silicon nitride layer 23, and the low temperature silicon oxide layer 22 are prepared.
  • the thickness is 0.5 ⁇ m; or the thicknesses of the first silicon nitride layer 21 and the second silicon nitride layer 23 are both 1.5 ⁇ m, and the thickness of the silicon oxide layer 22 prepared at a low temperature is 0.2 ⁇ m; or the first silicon nitride layer 21
  • the thickness of the second silicon nitride layer 23 is 1 ⁇ m, and the thickness of the silicon oxide layer 22 prepared at a low temperature is 0.2 ⁇ m or the like.
  • Step S206 forming a bottom electrode on the composite dielectric layer
  • Fig. 5A is a schematic cross-sectional view taken along the A-A plane after the bottom electrode is grown on the composite dielectric layer.
  • Figure 5B is a top plan view of the bottom electrode after growth on the composite dielectric layer.
  • a bottom electrode film is deposited on the second silicon nitride layer 23 by a metal thin film deposition technique, and the bottom electrode film is patterned by standard photolithography and etching processes to form the bottom electrode 31; or A photoresist is coated on the silicon nitride layer 23, and the photoresist is patterned by a standard photolithography process, then the bottom electrode metal film is deposited, and finally the photoresist is etched away by a lift-off technique to form the bottom electrode 31.
  • the intermediate portion of the patterned bottom electrode 31 is spoke-shaped and has a radiation center from which a plurality of strips are emitted, and a peripheral edge region is formed around the periphery.
  • the shape can be seen as shown in the pattern in FIG. 5B.
  • the above strips can be deformed according to actual needs, for example, changed to a fan shape, a wave shape or other shapes. Shapes conforming to radiation from one center to the periphery are all within the spoke-like protection of the present disclosure. Additionally, the present disclosure does not limit the distribution of the plurality of strips of the radiation.
  • the plurality of strips radiated from the center of the radiation may be uniformly distributed or unevenly distributed, preferably evenly distributed.
  • the material of the bottom electrode 31 is optional but not limited to one or a combination of the following materials: aluminum, gold/chromium composite layer, or platinum/titanium composite layer, wherein, preferably, the thickness of the aluminum electrode is between 0.01 Between ⁇ m and 5 ⁇ m, the thickness of the chromium layer or the titanium layer is between 0.01 ⁇ m and 1 ⁇ m, and the thickness of the gold layer or the platinum layer is between 0.05 ⁇ m and 5 ⁇ m.
  • the bottom electrode 31 is an aluminum electrode having a thickness of 0.2 ⁇ m or 0.3 ⁇ m; or the bottom electrode 31 is a gold/chromium composite layer having a thickness corresponding to 0.2 ⁇ m / 0.02 ⁇ m or 0.3 ⁇ m / 0.05 ⁇ m;
  • the electrode 31 is made of a platinum/titanium composite layer, and the thickness thereof corresponds to 0.2 ⁇ m/0.05 ⁇ m or 0.3 ⁇ m/0.05 ⁇ m, respectively.
  • Step S208 forming a piezoelectric layer on the bottom electrode
  • Fig. 6A is a schematic cross-sectional view taken along the A-A plane after the piezoelectric layer is grown on the bottom electrode.
  • Fig. 6B is a plan view of the piezoelectric layer grown on the bottom electrode.
  • a piezoelectric layer material is deposited on the bottom electrode 31, and a patterned piezoelectric layer 32 is formed by a standard photolithography etching process or a lift-off process.
  • the patterned piezoelectric layer 32 has the same shape as the intermediate portion of the bottom electrode 31, and is also spoke-like, having a radiation center from which a plurality of strips are emitted, as shown in the pattern in FIG. 6B. .
  • the piezoelectric layer 32 is made of zinc oxide and has a thickness of 1 ⁇ m, 2 ⁇ m or 3 ⁇ m; or the piezoelectric layer 32 is made of lead zirconate titanate and has a thickness of 4 ⁇ m; or the piezoelectric layer 32 is made of an organic piezoelectric material having a thickness of 1 ⁇ m. Or 2 ⁇ m; or the piezoelectric layer 32 is made of a relaxed ferroelectric material and has a thickness of 1 ⁇ m; or the piezoelectric layer 32 is made of aluminum nitride and has a thickness of 2 ⁇ m.
  • Step S210 forming an insulating isolation layer around the piezoelectric layer
  • Fig. 7A is a schematic cross-sectional view taken along the A-A plane after the insulating spacer is grown around the piezoelectric layer.
  • Fig. 7B is a plan view of the insulating spacer layer grown around the piezoelectric layer.
  • an insulating spacer layer is deposited on the front surface of the substrate 10, and patterned, and an insulating spacer layer 40 is formed around the piezoelectric layer, and the patterned insulating spacer layer is distributed around the piezoelectric layer, covering The edge region of the bottom electrode 31 is to isolate the bottom electrode 31 and the top electrode 33 and support the top electrode 33.
  • the thickness of the insulating isolation layer 40 prepared in this embodiment is the same as the thickness of the piezoelectric layer 32, as shown in FIG. 7A. It should be noted that the present disclosure does not limit the thickness of the insulating isolation layer and the range of coverage of the bottom electrode, and is merely described herein.
  • the insulating isolation layer functions to isolate the top electrode from the bottom electrode and to support the top electrode, as long as other structures or materials that can perform the same function are within the protection scope of the present disclosure.
  • the insulating isolation layer 40 is selected from the group consisting of polyxylene, silicon nitride, silicon oxide, polyimide, or piezoelectric materials;
  • Step S212 forming a top electrode over the piezoelectric layer and the insulating isolation layer;
  • Fig. 8A is a schematic cross-sectional view taken along line A-A after forming a top electrode over the piezoelectric layer and the insulating spacer.
  • Fig. 8B is a plan view showing the formation of a top electrode over the piezoelectric layer and the insulating spacer.
  • a top electrode film layer is deposited on the piezoelectric layer and the insulating isolation layer by a metal thin film deposition technique, and the top electrode film layer is patterned by a standard photolithography etching process to form a top electrode 32.
  • a photoresist on the piezoelectric layer and the insulating isolation layer, patterning the photoresist by a standard photolithography process, then depositing a top electrode metal film, and finally etching the photoresist by a lift-off technique to form a top electrode 32.
  • the top electrode 33 is deposited on the piezoelectric layer 32 and a portion of the insulating isolation layer 40, covering the piezoelectric layer 32 and a portion of the insulating isolation layer 40, the pattern of which is also spoke-shaped, and the spokes thereof.
  • the gap between the gaps coincides with the gap between the piezoelectric layer 32 and the spokes of the bottom electrode 31 to expose the second silicon nitride layer 23 on the top layer of the lower composite dielectric film layer 20; in addition, the top electrode 33 and the bottom are facilitated.
  • the electrical connection between the electrodes 31 is further provided with a lead end on the pattern of the top electrode 33, as shown in the shape shown in Fig. 8B.
  • the top electrode 33 is an aluminum electrode having a thickness of 0.2 ⁇ m or 0.3 ⁇ m; or the top electrode 33 is a platinum/titanium composite layer having a thickness corresponding to 0.2 ⁇ m/0.05 ⁇ m; or the top electrode 33 is made of gold.
  • the thickness of the /chromium composite layer corresponds to 0.2 ⁇ m / 0.05 ⁇ m or 0.3 ⁇ m / 0.05 ⁇ m, respectively.
  • Step S214 etching away the composite dielectric layer of the partial region to form a structural trench, and the unetched region forms a spoke-shaped structural beam;
  • FIG. 9A is a schematic cross-sectional view taken along line B-B of the composite dielectric layer after forming the structural trench.
  • FIG. 9B is a plan view of the etched composite dielectric layer forming a structural trench.
  • Drying or wet etching sequentially etching a portion of the composite dielectric layer to form a structure trench, the etching depth and the thickness of the sum of the first silicon nitride layer, the silicon oxide layer and the second silicon nitride layer Similarly, the number of structural slots is 2-30. In some examples, the number of preferred structural grooves is: 10, 9, 8, 6, 5, 4, 3, 2, and the like.
  • a portion of the second silicon nitride layer 23, the silicon oxide layer 22, and the first silicon nitride layer 21 are sequentially etched away along the BB cross-section, up to the upper surface of the substrate 10, as shown in FIG.
  • Fig. 9B the structural grooves are obtained, and the depth of the etching is indicated by a double-headed arrow below the broken line in Fig. 9A.
  • the composite dielectric film layer 40 under the gap portion between the spokes corresponding to the patterned top electrode 33, the piezoelectric layer 32, and the bottom electrode 31 is etched, and the remaining unetched regions are formed.
  • a consistent spoke-shaped structural beam, the BB profile of the radiation center of the structural beam is shown in FIG.
  • the structural beam includes, in order from bottom to top, a first silicon nitride layer 21, a silicon oxide layer 22, and a second nitrogen.
  • the silicon layer 23, the bottom electrode 31, the piezoelectric layer 32, and the top electrode 33 comprise, in order from bottom to top, a composite dielectric layer 20 and a piezoelectric unit 30.
  • the gap portion between the structural beams is the structural groove 70, and the nominal thickness of the structural groove obtained here is equal to the sum of the thicknesses of the composite dielectric layer 20 and the piezoelectric layer 30, which is different from the depth of the above etching.
  • Step S216 filling the filling sacrificial layer in the structure slot
  • Fig. 10A is a schematic cross-sectional view taken along line B-B after forming a sacrificial layer in the structure trench.
  • Fig. 10B is a plan view showing the formation of a filling sacrificial layer in the structure trench.
  • zinc oxide is used as the filling sacrificial layer 71
  • a zinc oxide film is deposited in the structural trench 70, and patterned by a stripping or etching process to fill the zinc oxide in the structural trench 70, as shown in FIG. 10A and FIG. 10B.
  • the material filling the sacrificial layer may be selected from, but not limited to, metal oxide, porous silicon, polycrystalline silicon, or the like.
  • the height of the filling sacrificial layer 71 is aligned with the height of the structural beam, but the present disclosure does not limit the height of the filling sacrificial layer, as long as the filling can be realized in the actual process and the organic vibrating film layer can be formed thereon. All are within the protection scope of the present disclosure.
  • Step S218 forming an organic vibration film layer over the filling sacrificial layer and the structural beam;
  • FIG. 11A is a schematic cross-sectional view taken along line B-B after forming an organic vibrating film layer over the filling sacrificial layer.
  • FIG. 11B is a plan view of the organic vibration film layer formed above the filling sacrificial layer.
  • a soft organic vibrating film 50 is deposited over the sacrificial layer and the structural beam, and patterned into the shape shown in FIG. 11B, covering the top electrode 33 except the lead end.
  • the part is coated with photoresist on the front side.
  • the organic vibrating membrane layer of the present disclosure may cover the entire hollow region or cover only a partial region including the structural trough, and may be adapted according to actual needs.
  • the organic vibrating film layer 50 is made of polyimide and has a thickness of 1 ⁇ m, 1.5 ⁇ m or 2 ⁇ m; or the organic vibrating film layer 50 is made of parylene, polyurethane, and has a thickness of 1 ⁇ m, 1.5 ⁇ m or 2 ⁇ m, etc. It should be noted that the material of the organic vibrating membrane 50 may be other organic membrane materials, and is not limited to the embodiment.
  • the patterned organic vibrating film layer 50 has a circular shape, and the shape of the hollow region in the central portion of the substrate 10 is also etched into a circular shape, and the two correspond to each other.
  • the hollow region of the central region of the substrate may have a square shape or other shape, and may be adaptively modified or adjusted according to the actual needs of the speaker.
  • the shape of the organic diaphragm layer may also be performed according to actual needs. Adaptive modifications or adjustments, including hollow regions of various shapes and organic diaphragm layers, are within the scope of the present disclosure.
  • Step S220 pattern etching the mask layer and the substrate on the back surface of the substrate to form a hollow region of a central portion corresponding to the organic vibration film layer;
  • FIG. 12 is a schematic cross-sectional view taken along line B-B after etching the back oxide layer to form a mask layer.
  • Fig. 13 is a schematic cross-sectional view taken along line B-B of the base etching.
  • a photoresist is coated on the oxide layer on the back surface of the substrate, and the photoresist is patterned by double-sided exposure technology and standard photolithography, and patterned by dry or wet etching.
  • the back oxide layer and the photoresist are removed to form a patterned oxide layer comprising a hollow region in a central region corresponding to the mechanical diaphragm layer.
  • the central region of the substrate is further etched by a wet or dry etching process, and as a result, as shown in Fig. 13, a substrate 10 having a central region as a hollow region is formed.
  • Step S222 forming a bottom electrode pressing hole on the front surface of the substrate
  • a photoresist is coated on the front surface of the substrate, and the insulating isolation layer 40 is patterned and etched to form a bottom electrode bonding hole 41. As shown in FIG. 1A and FIG. 1C, the bottom electrode bonding hole 41 is formed to make the bottom electrode. It is exposed to facilitate subsequent wiring work between the top electrode 33 and the bottom electrode 31.
  • Step S224 removing the filling sacrificial layer to complete preparation of the MEMS piezoelectric speaker
  • Figure 14 is a cross-sectional view of the MEMS piezoelectric speaker taken along the B-B plane after the sacrificial layer is etched.
  • Figure 15 is a cross-sectional view of the MEMS piezoelectric speaker taken along the A-A plane after the sacrificial layer is etched.
  • the filling sacrificial layer is removed by wet etching to obtain a released organic vibrating membrane supported by the structural beam, and the gap between the structural beams is a structural groove, see FIG. 14
  • the top view and the bottom view of the obtained MEMS piezoelectric speaker are shown in Figs. 1C and 1D, respectively.
  • the present disclosure provides a MEMS piezoelectric speaker and a method for fabricating the same, which are supported by a structural beam under a diaphragm of a MEMS piezoelectric speaker, and the structural beam is distributed in a spoke shape, and the structural beam includes a pressure.
  • the electric unit, the gap portion between the structural beams is a structural groove, the structural groove releases the stress of the diaphragm located above it, and the piezoelectric unit on the structural beam is easy to generate a large amplitude under the action of the electric load.
  • the vibration thereby increasing the sensitivity of the piezoelectric speaker; in addition, the use of the organic diaphragm layer as the top layer, suspended above the structure groove, while substantially not affecting the vibration amplitude, but also increases the radiation area of the diaphragm, significantly improving the sensitivity.
  • the MEMS piezoelectric speaker and the preparation method thereof of the present disclosure further include other processes and steps according to actual needs, and are not described herein because they are not related to the innovation of the present disclosure.
  • the directional terms mentioned in the embodiments such as “upper”, “lower”, “front”, “back”, “left”, “right”, etc., are only referring to the directions of the drawings, not It is intended to limit the scope of protection of the present disclosure.
  • the same elements are denoted by the same or similar reference numerals. Conventional structures or configurations will be omitted when it may cause confusion to the understanding of the present disclosure.
  • the shapes and sizes of the components in the drawings do not reflect the true size and proportion, but merely illustrate the contents of the embodiments of the present disclosure.
  • any reference signs placed between parentheses should not be construed as a limitation.

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Abstract

一种MEMS压电扬声器及其制备方法。其中，MEMS压电扬声器，包括：基底（10），其中央区域为空心区域；有机振动膜层（50），位于基底（10）的空心区域的上方，与基底（10）存在间距；以及结构梁，呈辐条状分布，形成于基底（10）之上，支撑有机振动膜层（50），该结构梁自下而上依次包含：复合介质层（20）和压电单元（30），在结构梁之间的空隙部分为结构槽（70）；其中，结构梁和有机振动膜层（50）构成压电复合振动膜。该MEMS压电扬声器的结构槽（70）使得压电复合振动膜的应力得到释放，同时结构梁上的压电单元在电负载的作用下，容易使整个压电复合振动膜产生较大幅度的振动，从而提高压电扬声器的灵敏度。

Description

MEMS压电扬声器及其制备方法 技术领域
本公开涉及微电子机械系统技术领域，尤其涉及一种MEMS压电扬声器及其制备方法。
背景技术
微机电系统(MEMS，Microelectro Mechanical Systems)器件是采用微电子和微机械加工技术制造出来的新型器件。与传统的器件相比，它具有体积小、重量轻、成本低、功耗低、可靠性高、适于批量化生产、易于集成和实现智能化的特点。MEMS扬声器具有体积小、功率小等优点。MEMS扬声器按照工作原理进行分类主要包括：MEMS电磁式扬声器和压电式扬声器。MEMS压电式扬声器具有功耗低、加工工艺简单等优点。但是灵敏度低是影响MEMS扬声器产业化的一个主要原因。推动MEMS压电扬声器的产业化意味着需要提高MEMS压电扬声器的灵敏度，因此提高MEMS压电扬声器的灵敏度是MEMS压电扬声器的产业化进程中亟需解决的技术问题。
发明内容
(一)要解决的技术问题
针对上述问题，本公开提供了一种MEMS压电扬声器及其制备方法，以提高MEMS压电扬声器的灵敏度。
(二)技术方案
根据本公开的一个方面，本公开提供了一种MEMS压电扬声器，包括：基底，其中央区域为空心区域；有机振动膜层，位于基底的空心区域的上方，与基底存在间距；以及结构梁，呈辐条状分布，形成于基底之上，支撑有机振动膜，该结构梁自下而上依次包含：复合介质层和压电单元，在结构梁之间的空隙部分为结构槽；其中，所述结构梁和有机振动膜层构成压电复合振动膜。
在本公开的一些实施例中，压电单元自下而上依次包括：底电极、压电层、以及顶电极；或者该压电单元自下而上依次包括：底电极、压电层、以及顶电极，且在底电极与压电层或顶电极与压电层之间至少存在一绝缘 隔离层。
在本公开的一些实施例中，压电层的材料为以下材料中的一种或几种：氧化锌、氮化铝、锆钛酸铅、驰豫型压电材料、钙钛矿型压电材料、或有机压电材料；和/或底电极和顶电极为：金属单层膜、金属多层膜、非金属导电膜、或金属与非金属导电膜的组合。
在本公开的一些实施例中，压电层的厚度介于0.01μm～60μm之间；和/或底电极和顶电极的厚度介于0.01μm～5μm之间。
在本公开的一些实施例中，有机振动膜层的材料为如下材料中的一种：聚酰亚胺、聚对二甲苯、聚氨酯、或者其它有机膜；和/或有机振动膜层的厚度介于0.01μm～30μm之间；和/或复合介质层自下而上依次包括：第一氮化硅层、氧化硅层、以及第二氮化硅层；第一氮化硅层、氧化硅层以及第二氮化硅层的厚度分别介于0.01μm～30μm之间；或者复合介质层自下而上依次包括：第一氧化硅层、氮化硅层、以及第二氧化硅层；和/或该第一氧化硅层、氮化硅层以及第二氧化硅层的厚度分别介于0.01μm～30μm之间；或者复合介质层自下而上依次包括：硅层、氧化层，或氧化层、硅层、氧化层；和/或该硅层和氧化层的厚度分别介于0.01μm～30μm之间；或者复合介质层为包含氮化硅层、氧化硅层、多晶硅、磷硅玻璃、硼硅玻璃中的一种或者是其中两种或多种任意组合的单层或者多层结构，和/或该氮化硅层、氧化硅层、多晶硅、磷硅玻璃、硼硅玻璃的厚度分别介于0.01μm～30μm之间。
在本公开的一些实施例中，该MEMS压电扬声器，还包括：掩膜层，用于干法或湿法体刻蚀，位于基底的背面；以及绝缘隔离层，形成于底电极之上，位于压电层周围，支撑顶电极，并隔离底电极与顶电极；其中，复合介质层、底电极、绝缘隔离层以及位于绝缘隔离层上方的顶电极构成外框，该外框与结构梁共同实现对有机振动膜的支撑。
在本公开的一些实施例中，在绝缘隔离层上包含一开口，使得底电极暴露出来，该开口为底电极压焊孔。
在本公开的一些实施例中，结构槽的数量介于2～30个之间。
根据本公开的另一个方面，本公开还提供了一种MEMS压电扬声器的制备方法，该制备方法包括：在基底正面制作呈辐条状分布的结构梁， 该结构梁自下而上依次包含：复合介质层和压电单元，在结构梁之间的空隙部分为结构槽；在结构梁上方制作有机振动膜层；以及刻蚀基底，使有机振动膜层正对的基底的中央区域为空心区域。
在本公开的一些实施例中，在基底正面制作结构梁，包括：在基底正面形成复合介质层；在复合介质层上依次形成图案化的底电极和压电层，该图案化的底电极的中间区域呈辐条状分布，周围形成与之连续的边缘区域，该图案化的压电层位于底电极的中间区域上方，与底电极中间区域的形状相同，大小可调整；在压电层的周围形成绝缘隔离层；在压电层和绝缘隔离层上方形成图案化的顶电极，该图案化的顶电极呈辐条状分布，所述图案化的顶电极与图案化的底电极和压电层的形状相同，大小可调整；以及刻蚀掉辐条之间的间隙下方的复合介质层，形成结构槽，未被刻蚀的区域形成辐条状分布的结构梁；在结构梁上方制作有机振动膜层，有机振动膜层覆盖整个空心区域或者仅覆盖包含结构槽上方的部分区域。以及刻蚀基底，使有机振动膜层正对的基底的中央区域为空心区域，包括：将填充牺牲层填充于结构槽，在结构梁和填充牺牲层上方沉积有机振动膜，在背面沉积用于干法或者湿法体刻蚀的掩膜层，图形化掩膜层，进行体刻蚀，使有机振动膜层正对的基底的中央区域为空心区域，并去除填充牺牲层；所述用于干法或者湿法体刻蚀的掩膜层在最终的器件中保留或者去除；在压电单元的顶电极上还包含一引线端，对应在绝缘隔离层上制备一开口，使得底电极暴露出来，该开口为底电极压焊孔。
(三)有益效果
从以上技术方案可以看出，本公开提供的MEMS压电扬声器及其制备方法具有下列有益效果：
(1)在MEMS压电扬声器的振动膜下方采用结构梁实现支撑，且结构梁呈辐条状分布，该结构梁包含压电单元，在结构梁之间的空隙部分为结构槽，该结构槽使得振动膜的应力得到释放，同时结构梁上的压电单元在电负载的作用下，压电复合振动膜容易产生较大幅度的振动，从而提高压电扬声器的灵敏度；
(2)采用有机振动膜层作为顶层，悬于结构槽上方，在基本不影响振动幅度的同时，又增加了振动膜的辐射面积，明显提高了灵敏度。
附图说明
图1A-图1D为根据本公开一实施例所示的含有4个结构槽和4个结构梁的MEMS压电扬声器的各个视图。
图1A为根据本公开一实施例所示的MEMS压电扬声器沿着A-A面剖开的剖面示意图。
图1B为根据本公开一实施例所示的MEMS压电扬声器沿着B-B面剖开的剖面示意图。
图1C为根据本公开一实施例所示的MEMS压电扬声器的俯视图。
图1D为根据本公开一实施例所示的MEMS压电扬声器的仰视图。
图2为根据本公开一实施例所示的MEMS压电扬声器的制备方法流程图。
图3-图15为制备MEMS压电扬声器的各个步骤对应的结构示意图。
图3为在基片上生长氧化层后沿着A-A面剖开的剖面示意图。
图4为在基底正面生长复合介质层后沿着A-A面剖开的剖面示意图。
图5A为在复合介质层上生长底电极后沿着A-A面剖开的剖面示意图。
图5B为在复合介质层上生长底电极后的俯视图。
图6A为在底电极上生长压电层后沿着A-A面剖开的剖面示意图。
图6B为在底电极上生长压电层后的俯视图。
图7A为在压电层周围生长绝缘隔离层后沿着A-A面剖开的剖面示意图。
图7B为在压电层周围生长绝缘隔离层后的俯视图。
图8A为在压电层和绝缘隔离层上方形成顶电极后沿着A-A面剖开的剖面示意图。
图8B为在压电层和绝缘隔离层上方形成顶电极后的俯视图。
图9A为刻蚀复合介质层形成结构槽后沿着B-B面剖开的剖面示意图。
图9B为刻蚀复合介质层形成结构槽后的俯视图。
图10A为在结构槽内形成填充牺牲层后沿着B-B面剖开的剖面示意图。
图10B为在结构槽内形成填充牺牲层后的俯视图。
图11A为在填充牺牲层上方形成有机振动膜层后沿着B-B面剖开的 剖面示意图。
图11B为在填充牺牲层上方形成有机振动膜层后的俯视图。
图12为刻蚀背面氧化层形成掩膜层后沿着B-B面剖开的剖面示意图。
图13为进行基底刻蚀后沿着B-B面剖开的剖面示意图。
图14为填充牺牲层腐蚀后，MEMS压电扬声器沿着B-B面剖开的剖面示意图。
图15为填充牺牲层腐蚀后，MEMS压电扬声器沿着A-A面剖开的剖面示意图。
【符号说明】
10-基底；
20-复合介质层；
21-第一氮化硅层；           22-氧化硅层；
23-第二氮化硅层；
30-压电单元；
31-底电极；                 32-压电层；
33-顶电极；
40-绝缘隔离层；             41-底电极压焊孔；
50-有机振动膜层；           60-掩膜层；
70-结构槽；                 71-填充牺牲层。
具体实施方式
为使本公开的目的、技术方案和优点更加清楚明白，以下结合具体实施例，并参照附图，对本公开进一步详细说明。
需要说明的是，在附图或说明书描述中，相似或相同的部分都使用相同的图号。且在附图中，实施例的形状或是厚度可扩大，并以简化或是方便标示。再者，附图中未绘示或描述的元件或实现方式，为所属技术领域中普通技术人员所知的形式。另外，虽然本文可提供包含特定值的参数的示范，但应了解，参数无需确切等于相应的值，而是可在可接受的误差容限或设计约束内近似于相应的值。
目前灵敏度低是影响MEMS扬声器产业化的一个主要原因，而振动膜的应力高，振动幅度低是造成灵敏度低的直接原因。通过结构和制备技 术优化，增加MEMS扬声器的振动幅度和辐射声压，从而提高灵敏度，有助于推动MEMS压电扬声器的产业化。
本公开提供了一种MEMS压电扬声器及其制备方法，在MEMS压电扬声器的振动膜下方采用结构梁实现支撑，且结构梁按照辐条状进行分布，在结构梁之间为结构槽，该结构槽使得位于其上方的振动膜的应力得到释放，同时结构梁上的压电单元在电负载的作用下，压电复合振动膜容易产生较大幅度的振动，从而提高压电扬声器的灵敏度。
本公开中，术语“基底的背面”在附图中对应为基底的下表面，“基底的正面”对应为基底的上表面；数值范围“介于之间”包括端点值。
在本公开的第一个示例性实施例中，提供了一种MEMS压电扬声器。
图1A-图1D为根据本公开一实施例所示的含有4个结构槽和4个结构梁的MEMS压电扬声器的各个视图。其中，图1A为根据本公开一实施例所示的MEMS压电扬声器沿着A-A面剖开的剖面示意图；图1B为根据本公开一实施例所示的MEMS压电扬声器沿着B-B面剖开的剖面示意图；图1C为根据本公开一实施例所示的MEMS压电扬声器的俯视图；图1D为根据本公开一实施例所示的MEMS压电扬声器的仰视图。
参照图1A-图1D所示，本公开的MEMS压电扬声器，包括：基底10，其中央区域为空心区域；掩膜层60，位于基底10的背面；有机振动膜层50，位于基底10的空心区域的上方，与基底10存在间距；以及结构梁，呈辐条状分布，形成于基底10之上，支撑有机振动膜50，该结构梁自下而上依次包含：复合介质层20和压电单元30，在结构梁之间的空隙部分为结构槽70；其中，该结构梁和有机振动膜层50构成压电复合振动膜。
下面结合附图来对本公开的MEMS压电扬声器的各部分进行详细介绍。
本实施例中，基底10为硅基底。但本公开的基底10不局限于实施例的举例，还可以是SOI基片或者其他基片，为了得到不同的复合介质层20，根据实际需要进行基底10的选择。
参照图1A所示，本实施例中，复合介质层20自下而上依次包括：第一氮化硅层21、氧化硅层22、以及第二氮化硅层23，其中，氧化硅层优选采用低温条件下生长的氧化硅层。第一氮化硅层21、氧化硅层22以及 第二氮化硅层23的厚度分别介于0.01μm～30μm之间。
需要说明的是，本公开的复合介质层20的层数不做限制，每层的材料也不局限于上述实施例。可以根据实际需要对复合介质层的层数和各层材料进行选择。比如说，在一实例中，复合介质层20自下而上依次包括：第一氧化硅层、氮化硅层、以及第二氧化硅层。优选的，该第一氧化硅层、氮化硅层以及第二氧化硅层的厚度分别介于0.01μm～30μm之间。或者在一实例中，复合介质层自下而上依次包括：硅层、氧化层或氧化层、硅层、氧化层。优选的，硅层和氧化层的厚度分别介于0.01μm～30μm之间。或者在一实例中，复合介质层为包含氮化硅层、氧化硅层、多晶硅、磷硅玻璃、硼硅玻璃中的一种或者是其中任意两种的单层或者多层结构。优选的，氮化硅层、氧化硅层、多晶硅、磷硅玻璃、硼硅玻璃的厚度分别介于0.01μm～30μm之间。
参照图1B所示，本实施例中，压电单元30自下而上依次包括：底电极31、压电层32、以及顶电极33。在其它实施例中，在压电单元的电极和压电层之间还可以包括绝缘隔离层。底电极31和顶电极32为：金属单层膜、金属多层膜、非金属导电膜、或金属与非金属导电膜的组合。本实施例中，压电层32的材料可选但不限于以下材料中的一种或几种：氧化锌、氮化铝、锆钛酸铅、驰豫型压电材料、钙钛矿型压电材料、或有机压电材料；压电层的厚度介于0.01μm～60μm之间。底电极31和顶电极33的材料可选但不限于如下材料之一或其组合：铝、铜、金、铂、钼、铬、钛、镍酸镧(LNO)以及其它金属或非金属导电膜，当底电极和顶电极为金属或非金属导电膜时，厚度介于0.01μm～5μm之间。底电极31和顶电极33也可以为铝、金/铬复合层、或者铂/钛复合层，所述底电极或顶电极的粘附层为铬层、钛层、或者其它导电膜层时，厚度介于0.01μm～1μm之间。
其中，优选的，铝电极的厚度介于0.01μm～5μm之间，铬层或钛层的厚度介于0.01μm～1μm之间，金层或铂层的厚度介于0.05μm～5μm之间。
需要说明的是，实施例中所列举的压电层、底电极、以及顶电极的结构和材料仅作为示例进行说明，凡是能起到压电功能、电极功能的其它新型材料和结构均在本公开的压电单元的保护范围之内。
本实施例中，底电极31为图案化的形状，中间区域呈辐条状分布，周围形成与之连续的边缘区域，参见图5B所示。压电层32覆盖于底电极31的中间区域，也呈辐条状分布，参见图6B所示。顶电极33为图案化的形状，覆盖于压电层32之上，并超出压电层32的外围，即超出底电极31的中间区域，出于便于进行顶电极33与底电极31之间的电性连接的目的，将顶电极33的图案设置为如图8B所示的形状，在顶电极33的图案上设有一引线端。需要说明的是，底电极、压电层、顶电极的大小可以进行适应性调整。
在本公开的其它实施例中，参照图1A和图1B所示，该MEMS压电扬声器还包括：绝缘隔离层40，形成于底电极31之上，位于压电层32周围，支撑顶电极33，并隔离底电极31与顶电极33；顶电极33的引线端位于该绝缘隔离层40之上；复合介质层30、底电极31、绝缘隔离层40以及部分顶电极33构成外框，与结构梁共同实现对有机振动膜50的支撑。需要说明的是，绝缘隔离层的作用是实现底电极和顶电极之间的隔离和顶电极的支撑，其高度、覆盖底电极的范围大小、以及材料均不作限制，只要能起到上述作用即可；另外，在一些实施例中，该MEMS压电扬声器可以不含有绝缘隔离层，改变原来的压电层的图案，使其不仅仅覆盖于底电极的中间区域，在底电极的边缘区域也沉积压电层，从而使位于底电极的边缘区域的压电层起到绝缘隔离层的作用。在一些实例中，绝缘隔离层40的材料可选但不限于如下材料中的一种：氧化硅、氮化硅、聚酰亚胺、聚对二甲苯、聚氨酯、或压电材料等。
本实施例中，有机振动膜层50的材料可选但不限于如下材料中的一种：聚酰亚胺、聚对二甲苯、聚氨酯、或其他有机膜；有机振动膜层50的厚度介于0.01μm～10μm之间。
参照图1C所示，本实施例中，优选的，有机振动膜层50的形状为圆形，基底10的中央区域的空心区域的形状也为圆形，二者互相对应。在其它实施例中，基底的中央区域的空心区域的形状可以为方形或其他形状，可根据扬声器的实际需要进行适应性修改或调整，相应的，有机振动膜层的形状与空心区域的形状相同，也可根据实际需要进行适应性修改或调整，包含各个形状的空心区域和有机振动膜层的扬声器均在本公开的保护范 围之内。
本实施例中，掩膜层60的厚度介于0.01μm～20μm之间。
结构梁呈辐条状分布，对应的结构槽的数量介于2～30之间，本实施例中，结构槽的数目为4个。该辐条中心的部分有助于增强支撑的强度。
在本公开的其它实施例中，为了便于将底电极31与顶电极33进行电性连接，在MEMS压电扬声器的器件中设置有底电极压焊孔41。参照图1A和图1C所示，在绝缘隔离层40上具有一开口，使得底电极31暴露出来，该开口为底电极压焊孔41，便于器件进行顶电极33与底电极31之间的电性连接。
在本公开的第二个示例性实施例中，提供了一种MEMS压电扬声器的制备方法。
图2为根据本公开一实施例所示的MEMS压电扬声器的制备方法流程图。图3-图15为制备MEMS压电扬声器的各个步骤对应的结构示意图。
参照图2、图3-图15所示，本公开的MEMS压电扬声器的制备方法，包括：
步骤S202：在基底背面形成掩膜层；
本实施例中，以氧化层作为掩膜层60进行示例说明，本公开的掩膜层还可以是其他掩膜层，不以此为限。
本实施例中，该步骤S202包括：在基底的上、下表面沉积氧化层，然后去除上表面的氧化层，得到背面含有氧化层的基底。
图3为在基片上生长氧化层后沿着A-A面剖开的剖面示意图。
本实施例中，针对复合介质层20为第一氮化硅层21、氧化硅层22和第二氮化硅层23，进行基底10的选择，确定基底采用硅材料。首先，用标准清洗方法对基底硅进行清洗，分别利用酸性清洗液和碱性清洗液进行煮沸清洗，并用去离子水进行清洗，最后用氮气吹干；然后，利用热氧化炉分别在基底硅10的正面和背面上沉积氧化层作为掩膜层60，参见图3所示，在基底硅背面的掩膜层60上涂覆光刻胶，用湿法工艺去除正面的掩膜层60，最后去除背面的掩膜层60上的光刻胶。
但本公开的基底10不局限于实施例的举例，还可以是SOI基片或者其他基片。根据复合介质层20的膜层结构以及它与基底10之间的结合状 态、制备的难易程度等效果进行基底10和复合介质层20的匹配选择。
在一些实例中，掩膜层60的厚度分别为0.2μm、0.5μm、1μm、1.5μm、3μm或3.5μm等。
步骤S204：在基底上表面形成复合介质层；
图4为在基底正面生长复合介质层后沿着A-A面剖开的剖面示意图。
参照图4所示，利用等离子体化学气相沉积(PECVD)的方法先后在基底硅正面沉积第一氮化硅层21、氧化硅层22和第二氮化硅层23，形成复合介质层20，其中，氧化硅层22优选在低温条件下进行生长。针对其他实施例的复合介质层的材料，同样按照薄膜沉积技术比如PECVD的方法依次进行沉积，属于常规的制备工艺，这里不再赘述。
本实施例中，第一氮化硅层21、氧化硅层22以及第二氮化硅层23的厚度分别介于0.01μm～10μm之间。
在一些实例中，第一氮化硅层21和第二氮化硅层23的厚度均为0.5μm，低温制备的氧化硅层22的厚度为0.2μm；或者第一氮化硅层21和第二氮化硅层23的厚度均为1μm，低温制备的氧化硅层22的厚度为0.5μm；或者第一氮化硅层21、第二氮化硅层23以及的低温制备的氧化硅层22厚度均为0.5μm；或者第一氮化硅层21和第二氮化硅层23的厚度均为1.5μm，低温制备的氧化硅层22的厚度为0.2μm；或者第一氮化硅层21和第二氮化硅层23的厚度均为1μm，低温制备的氧化硅层22的厚度为0.2μm等。
步骤S206：在复合介质层上形成底电极；
图5A为在复合介质层上生长底电极后沿着A-A面剖开的剖面示意图。图5B为在复合介质层上生长底电极后的俯视图。
参照图5A和图5B所示，在第二氮化硅层23上用金属薄膜沉积技术沉积底电极膜，并用标准光刻和刻蚀工艺图案化底电极膜，形成底电极31；或者在第二氮化硅层23上涂覆光刻胶，并用标准光刻工艺图案化光刻胶，然后再沉积底电极金属膜，最后用剥离技术刻蚀掉光刻胶，形成底电极31。
该图案化的底电极31的中间区域呈辐条状分布，具有一个辐射中心，从该辐射中心发射出多个条形，周围形成与之连续的边缘区域，形状可参见图5B中的图案所示。当然，上述条形可以根据实际需要进行变形，例 如改为扇形、波浪形或者其他形状。符合从一个中心向四周辐射的形状均在本公开的辐条状的保护范围之内。另外，本公开也不限定该辐射的多个条形的分布。从辐射中心辐射出来的多个条形可以均匀分布，也可以不均匀分布，优选均匀分布。
本实施例中，底电极31的材料可选但不限于如下材料之一或其组合：铝、金/铬复合层、或者铂/钛复合层，其中，优选的，铝电极的厚度介于0.01μm～5μm之间，铬层或钛层的厚度介于0.01μm～1μm之间，金层或铂层的厚度介于0.05μm～5μm之间。
在一些实例中，底电极31选用铝电极，厚度为0.2μm或0.3μm；或者底电极31选用金/铬复合层，其厚度分别对应为0.2μm/0.02μm或0.3μm/0.05μm；或者底电极31选用铂/钛复合层，其厚度分别对应为0.2μm/0.05μm或0.3μm/0.05μm等。
步骤S208：在底电极上形成压电层；
图6A为在底电极上生长压电层后沿着A-A面剖开的剖面示意图。图6B为在底电极上生长压电层后的俯视图。
参照图6A和图6B所示，本实施例中，在底电极31上沉积压电层材料，并利用标准光刻刻蚀工艺或剥离工艺，形成图案化的压电层32。
该图案化的压电层32的形状与底电极31中间区域的形状相同，也呈辐条状分布，具有一个辐射中心，从该辐射中心发射出多个条形，参加图6B中的图案所示。
在一些实例中，压电层32选用氧化锌，厚度为1μm、2μm或3μm；或者压电层32选用锆钛酸铅，厚度为4μm；或者压电层32选用有机压电材料，厚度为1μm或2μm；或者压电层32选用弛豫铁电材料，厚度为1μm；或者压电层32选用氮化铝，厚度为2μm等。
步骤S210：在压电层的周围形成绝缘隔离层；
图7A为在压电层周围生长绝缘隔离层后沿着A-A面剖开的剖面示意图。图7B为在压电层周围生长绝缘隔离层后的俯视图。
参照图7A和图7B所示，在基片10的正面沉积绝缘隔离层，并且图案化，在压电层的周围形成绝缘隔离层40，图案化的绝缘隔离层分布在压电层周围，覆盖底电极31的边缘区域，以隔离底电极31和顶电极33，并 支撑顶电极33。其中，本实施例制备的该绝缘隔离层40的厚度与压电层32的厚度一样，如图7A所示。需要说明的是，本公开不限制该绝缘隔离层的厚度以及覆盖底电极的范围大小，这里仅作为示意进行说明。该绝缘隔离层起到隔离顶电极与底电极，并支撑顶电极的作用，只要能起到相同作用的其它结构或材料均在本公开的保护范围之内。
在一些实例中，该绝缘隔离层40选用对聚二甲苯、氮化硅、氧化硅、聚酰亚胺、或压电材料等；
步骤S212：在压电层和绝缘隔离层上方形成顶电极；
图8A为在压电层和绝缘隔离层上方形成顶电极后沿着A-A面剖开的剖面示意图。图8B为在压电层和绝缘隔离层上方形成顶电极后的俯视图。
本实施例中，在压电层和绝缘隔离层上，用金属薄膜沉积技术沉积顶电极膜层，并用标准光刻刻蚀工艺图案化该顶电极膜层，形成顶电极32。或者在压电层和绝缘隔离层上涂覆光刻胶，并用标准光刻工艺图案化光刻胶，然后再沉积顶电极金属膜，最后用剥离技术刻蚀掉光刻胶，形成顶电极32。
参照图8A和图8B所示，该顶电极33沉积于压电层32和部分绝缘隔离层40之上，覆盖压电层32和部分绝缘隔离层40，其图案也呈辐条状分布，其辐条之间的空隙与压电层32、底电极31的辐条之间的空隙位置重合，暴露出下方复合介质膜层20顶层的第二氮化硅层23；另外，为了便于进行顶电极33与底电极31之间的电性连接，在顶电极33的图案上还设置一引线端，参照图8B所示的形状所示。
在一些实例中，该顶电极33选用铝电极，厚度为0.2μm或0.3μm；或者该顶电极33选用铂/钛复合层，其厚度分别对应0.2μm/0.05μm；或者该顶电极33选用金/铬复合层，其厚度分别对应0.2μm/0.05μm或0.3μm/0.05μm等。
步骤S214：刻蚀掉部分区域的复合介质层，形成结构槽，未被刻蚀的区域形成辐条状分布的结构梁；
图9A为刻蚀复合介质层形成结构槽后沿着B-B面剖开的剖面示意图。图9B为刻蚀复合介质层形成结构槽后的俯视图。
利用干法或者湿法工艺刻蚀，依次刻蚀掉部分区域的复合介质层形成 结构槽，刻蚀的深度与第一氮化硅层、氧化硅层和第二氮化硅层之和的厚度相同，结构槽的数量为2-30个。在一些实例中，优选的结构槽的数量为：10个、9个、8个、6个、5个、4个、3个、2个等。
参照图9A所示，沿着B-B剖面来看，依次刻蚀掉部分区域的第二氮化硅层23、氧化硅层22和第一氮化硅层21，直至基底10的上表面，如图9B所示，得到结构槽，刻蚀的深度在图9A中以虚线以下的双向箭头标示。其中，对应图案化的顶电极33、压电层32、以及底电极31的辐条之间的空隙部分下方的复合介质膜层40被刻蚀，剩下的未被刻蚀的区域则形成了具有一致的辐条状分布的结构梁，图9A中显示出了该结构梁辐射中心的B-B剖面，该结构梁自下而上依次包含：第一氮化硅层21、氧化硅层22、第二氮化硅层23、底电极31、压电层32以及顶电极33，即自下而上依次包含：复合介质层20和压电单元30。整体来看，该结构梁之间的空隙部分即为结构槽70，这里得到的结构槽的名义厚度等于复合介质层20和压电层30的厚度之和，与上述刻蚀的深度不同。
步骤S216：将填充牺牲层填充于结构槽内；
图10A为在结构槽内形成填充牺牲层后沿着B-B面剖开的剖面示意图。图10B为在结构槽内形成填充牺牲层后的俯视图。
本实施例中，采用氧化锌作为填充牺牲层71，在结构槽70内沉积氧化锌膜，并用剥离或腐蚀工艺进行图形化制作，使氧化锌填充在结构槽70内，参照图10A和图10B所示。填充牺牲层的材料可选但不限于：金属氧化物、多孔硅、多晶硅等。本实施例中，优选的，填充牺牲层71的高度与结构梁的高度对齐，但本公开不限制填充牺牲层的高度，只要在实际工艺中能够实现填充并在其上方可以形成有机振动膜层，均在本公开的保护范围之内。
步骤S218：在填充牺牲层和结构梁上方形成有机振动膜层；
图11A为在填充牺牲层上方形成有机振动膜层后沿着B-B面剖开的剖面示意图。图11B为在填充牺牲层上方形成有机振动膜层后的俯视图。
参照图11A所示，本实施例中，在填充牺牲层和结构梁的上方沉积软的有机振动膜50，并将其图案化为图11B中所示形状，覆盖顶电极33除引线端之外的部分，并在正面涂覆光刻胶。
本公开的有机振动膜层可以覆盖整个空心区域或者仅覆盖包含结构槽上方的部分区域即可，可根据实际需要进行适应性修改。
在一些实例中，该有机振动膜层50选用聚酰亚胺，其厚度为1μm、1.5μm或2μm；或者该有机振动膜层50选用聚对二甲苯、聚氨酯，其厚度为1μm、1.5μm或2μm等。需要说明的是，有机振动膜50的材料还可以是其他有机膜材料，不局限于实施例。
优选的，图案化有机振动膜层50的形状为圆形，将基底10的中央区域的空心区域的形状也刻蚀为圆形，二者互相对应。在其它实施例中，基底的中央区域的空心区域的形状可以为方形或其他形状，可根据扬声器的实际需要进行适应性修改或调整，相应的，有机振动膜层的形状也可根据实际需要进行适应性修改或调整，包含各个形状的空心区域和有机振动膜层的扬声器均在本公开的保护范围之内。
步骤S220：图案化刻蚀基底背面的掩膜层和基底，形成与有机振动膜层对应的中央部分的空心区域；
图12为刻蚀背面氧化层形成掩膜层后沿着B-B面剖开的剖面示意图。图13为进行基底刻蚀后沿着B-B面剖开的剖面示意图。
参照图12所示，在基片背面的氧化层上涂覆光刻胶，并采用双面曝光技术和标准光刻技术图案化光刻胶，用干法或者湿法刻蚀工艺图案化刻蚀背面氧化层，并去除光刻胶，形成图案化的氧化层，该图案化的氧化层包含与机振动膜层对应的中央区域的空心区域。将该图案化的氧化层作为掩膜层60，进一步利用湿法或者干法刻蚀的工艺将基底的中央区域刻蚀，结果如图13所示，形成中央区域为空心区域的基底10。
步骤S222：在基底正面形成底电极压焊孔；
在基片正面涂敷光刻胶，并且图形化刻蚀绝缘隔离层40，刻蚀形成底电极压焊孔41，结合图1A和图1C所示，形成的底电极压焊孔41使得底电极暴露出来，便于器件后续进行顶电极33与底电极31之间的接线工作。
步骤S224：去除填充牺牲层，完成MEMS压电扬声器的制备；
图14为填充牺牲层腐蚀后，MEMS压电扬声器沿着B-B面剖开的剖面示意图。图15为填充牺牲层腐蚀后，MEMS压电扬声器沿着A-A面剖开的剖面示意图。
本实施例中，将填充牺牲层利用湿法腐蚀的方法去除，得到释放后的有机振动膜，该有机振动膜由结构梁支撑，在该结构梁之间的空隙部分为结构槽，参见图14与图15所示，得到的MEMS压电扬声器的俯视图和仰视图分别参照图1C和图1D所示。
综上所述，本公开提供了一种MEMS压电扬声器及其制备方法，通过在MEMS压电扬声器的振动膜下方采用结构梁实现支撑，且结构梁呈辐条状进行分布，该结构梁包含压电单元，在结构梁之间的空隙部分为结构槽，该结构槽使得位于其上方的振动膜的应力得到释放，同时结构梁上的压电单元在电负载的作用下，容易产生较大幅度的振动，从而提高压电扬声器的灵敏度；另外，采用有机振动膜层作为顶层，悬于结构槽上方，在基本不影响振动幅度的同时，又增加了振动膜的辐射面积，明显提高了灵敏度。
当然，根据实际需要，本公开的MEMS压电扬声器及其制备方法还包含其他的工艺和步骤，由于同本公开的创新之处无关，此处不再赘述。还需要说明的是，实施例中提到的方向用语，例如“上”、“下”、“前”、“后”、“左”、“右”等，仅是参考附图的方向，并非用来限制本公开的保护范围。贯穿附图，相同的元素由相同或相近的附图标记来表示。在可能导致对本公开的理解造成混淆时，将省略常规结构或构造。并且图中各部件的形状和尺寸不反映真实大小和比例，而仅示意本公开实施例的内容。另外，在权利要求中，不应将位于括号之间的任何参考符号构造成对权利要求的限制。
说明书与权利要求中所使用的序数例如“第一”、“第二”、“第三”等的用词，以修饰相应的元件，其本身并不意味着该元件有任何的序数，也不代表某一元件与另一元件的顺序、或是制造方法上的顺序，该些序数的使用仅用来使具有某命名的一元件得以和另一具有相同命名的元件能做出清楚区分。此外，除非特别描述或必须依序发生的步骤，上述步骤的顺序并无限制于以上所列，且可根据所需设计而变化或重新安排。并且上述实施例可基于设计及可靠度的考虑，彼此混合搭配使用或与其他实施例混合搭配使用，即不同实施例中的技术特征可以自由组合形成更多的实施例。
以上所述的具体实施例，对本公开的目的、技术方案和有益效果进行 了进一步详细说明，所应理解的是，以上所述仅为本公开的具体实施例而已，并不用于限制本公开，凡在本公开的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本公开的保护范围之内。

Claims (10)

  1. 一种MEMS压电扬声器，其特征在于，包括：
    基底，其中央区域为空心区域；
    有机振动膜层，位于基底的空心区域的上方，与基底存在间距；以及
    结构梁，呈辐条状分布，形成于基底之上，支撑有机振动膜，该结构梁自下而上依次包含：复合介质层和压电单元，在结构梁之间的空隙部分为结构槽；
    其中，所述结构梁和有机振动膜层构成压电复合振动膜。
  2. 根据权利要求1所述的MEMS压电扬声器，其中：
    所述压电单元自下而上依次包括：底电极、压电层、以及顶电极；或者
    所述压电单元自下而上依次包括：底电极、压电层、以及顶电极，且在底电极与压电层或顶电极与压电层之间至少存在一绝缘隔离层。
  3. 根据权利要求2所述的MEMS压电扬声器，其中：
    所述压电层的材料为以下材料中的一种或几种：氧化锌、氮化铝、锆钛酸铅、钙钛矿型压电材料、驰豫型压电材料、或有机压电材料；和/或
    所述底电极和顶电极为：金属单层膜、金属多层膜、非金属导电膜、或金属与非金属导电膜的组合。
  4. 根据权利要求3所述的MEMS压电扬声器，其中：
    所述压电层的厚度介于0.01μm～60μm之间；和/或
    所述底电极和顶电极的厚度介于0.01μm～5μm之间。
  5. 根据权利要求1所述的MEMS压电扬声器，其中：
    所述有机振动膜层的材料为如下材料中的一种：聚酰亚胺、聚对二甲苯、聚氨酯、或者其它有机膜；和/或
    所述有机振动膜层的厚度介于0.01μm～30μm之间；和/或
    所述复合介质层自下而上依次包括：第一氮化硅层、氧化硅层、以及第二氮化硅层；和/或所述第一氮化硅层、氧化硅层、以及第二氮化硅层的厚度分别介于0.01μm～30μm之间；
    或者所述复合介质层自下而上依次包括：第一氧化硅层、氮化硅层、 以及第二氧化硅层；和/或所述第一氧化硅层、氮化硅层以及第二氧化硅层的厚度分别介于0.01μm～30μm之间；
    或者所述复合介质层自下而上依次包括：硅层、氧化层，或氧化层、硅层、氧化层；和/或所述硅层和氧化层的厚度分别介于0.01μm～30μm之间；
    或者所述复合介质层为包含氮化硅层、氧化硅层、多晶硅、磷硅玻璃、硼硅玻璃中的一种或者是其中两种或多种任意组合的单层或者多层结构，和/或所述氮化硅层、氧化硅层、多晶硅、磷硅玻璃、硼硅玻璃的厚度分别介于0.01μm～30μm之间。
  6. 根据权利要求2所述的MEMS压电扬声器，还包括：
    掩膜层，用于干法或湿法体刻蚀，位于基底的背面；以及
    绝缘隔离层，形成于底电极之上，位于压电层周围，支撑顶电极，并隔离底电极与顶电极；
    其中，复合介质层、底电极、绝缘隔离层以及位于绝缘隔离层上方的顶电极构成外框，该外框与结构梁共同实现对有机振动膜的支撑。
  7. 根据权利要求6所述的MEMS压电扬声器，其中，在所述绝缘隔离层上包含一开口，使得底电极暴露出来，该开口为底电极压焊孔。
  8. 根据权利要求1至7任一项所述的MEMS压电扬声器，其中，所述结构槽的数量介于2～30个之间。
  9. 一种如权利要求1至8任一项所述的MEMS压电扬声器的制备方法，包括：
    在基底正面制作呈辐条状分布的结构梁，该结构梁自下而上依次包含：复合介质层和压电单元，在结构梁之间的空隙部分为结构槽；
    在结构梁上方制作有机振动膜层；以及
    刻蚀基底，使有机振动膜层正对的基底的中央区域为空心区域。
  10. 根据权利要求9所述的制备方法，其中：
    所述在基底正面制作呈辐条状分布的结构梁，包括：
    在基底正面形成复合介质层；
    在复合介质层上依次形成图案化的底电极和压电层，该图案化的底电极的中间区域呈辐条状分布，周围形成与之连续的边缘区域，该图案化 的压电层位于底电极的中间区域上方，与底电极中间区域的形状相同，大小可调整；
    在压电层的周围形成绝缘隔离层；
    在压电层和绝缘隔离层上方形成图案化的顶电极，该图案化的顶电极呈辐条状分布，所述图案化的顶电极与图案化的底电极和压电层的形状相同，大小可调整；以及
    刻蚀掉辐条之间的间隙下方的复合介质层，形成结构槽，未被刻蚀的区域形成辐条状分布的结构梁；
    所述在结构梁上方制作有机振动膜层，以及刻蚀基底，使有机振动膜层正对的基底的中央区域为空心区域，包括：将填充牺牲层填充于结构槽，在结构梁和填充牺牲层上方沉积有机振动膜，在背面沉积用于干法或者湿法体刻蚀的掩膜层，图形化掩膜层，进行体刻蚀，使有机振动膜层正对的基底的中央区域为空心区域，并去除填充牺牲层；所述用于干法或者湿法体刻蚀的掩膜层在最终的器件中保留或者去除；
    在所述压电单元的顶电极上还包含一引线端，对应在绝缘隔离层上制备一开口，使得底电极暴露出来，该开口为底电极压焊孔。
PCT/CN2018/074277 2018-01-26 2018-01-26 Mems压电扬声器及其制备方法 WO2019144370A1 (zh)

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JP2008035159A (ja) * 2006-07-28 2008-02-14 Star Micronics Co Ltd エレクトレットコンデンサマイクロホン
CN106028243A (zh) * 2015-03-25 2016-10-12 Dsp集团有限公司 微型扬声器声调制器
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