A MEMS structure

Abstract

The present application discloses a MEMS structure, comprising a back plate and a piezoelectric composite vibration layer separated by a cavity, wherein the back plate and the piezoelectric composite vibration layer form a capacitive structure, wherein the piezoelectric composite vibration layer comprises a vibration support layer, a first electrode layer, a piezoelectric layer, and a second electrode layer stacked in sequence. The MEMS structure combines the features of a piezoelectric MEMS microphone and a capacitive MEMS microphone, and under the condition of receiving equal sound energy, the MEMS structure obtains more converted electrical energy, thereby increasing the output electrical energy and obtaining a higher sensitivity.

Description

Technical Field

[0001] The present application relates to the technical field of acoustic-to-electric conversion devices, and more specifically, to a MEMS (Micro-Electro-Mechanical System) structure. Background Art

[0002] MEMS microphones mainly include capacitive and piezoelectric types. MEMS capacitive microphones use a diaphragm and a back plate to form a flat capacitor. The diaphragm vibrates under the action of sound waves, causing the distance between the diaphragm and the back plate to change, resulting in a change in the capacitance of the flat capacitor, thereby converting the sound wave signal into an electrical signal. MEMS piezoelectric microphones are microphones made using micro-electromechanical system technology and piezoelectric film technology. Due to the use of semiconductor planar technology and bulk silicon processing technology, they are small in size, small in volume, and have good consistency.

[0003] At present, capacitive MEMS microphones seem to have reached a performance bottleneck and have not made significant improvements in recent years; while the low sensitivity of piezoelectric MEMS microphones has restricted their development. Summary of the invention

[0004] In view of the problems in the related art, the present application proposes a MEMS structure that can achieve higher sensitivity and improve output energy.

[0005] The technical solution of this application is implemented as follows:

[0006] According to one aspect of the present application, a MEMS structure is provided, comprising a back plate and a piezoelectric composite vibration layer separated by a cavity, wherein the back plate and the piezoelectric composite vibration layer constitute a capacitor structure, wherein the piezoelectric composite vibration layer comprises a vibration support layer, a first electrode layer, a piezoelectric layer, and a second electrode layer stacked in sequence.

[0007] The back plate is formed above the substrate, the cavity is formed above the back plate, and the piezoelectric composite vibration layer is formed above the cavity.

[0008] The MEMS structure includes the substrate, a passivation layer formed on the substrate, the back plate formed on the passivation layer, a first spacing layer formed on the passivation layer and separated from the back plate, and the vibration support layer formed on the first spacing layer.

[0009] The piezoelectric composite vibration layer has a first through hole, the first through hole penetrates the vibration support layer, the first electrode layer, the piezoelectric layer and the second electrode layer, and the first through hole is connected to the cavity.

[0010] The piezoelectric composite vibration layer is formed above the substrate, the cavity is formed above the piezoelectric composite vibration layer, and the back plate is formed above the cavity.

[0011] The MEMS structure includes a barrier layer formed above the substrate, the vibration support layer, the first electrode layer, the piezoelectric layer and the second electrode layer formed in sequence above the barrier layer, a second spacer layer formed above the barrier layer and separated from the first electrode layer, and a back plate formed above the second spacer layer.

[0012] Wherein, the back plate includes a supporting structure layer and a polar plate layer above the supporting structure layer.

[0013] Wherein, the back plate has a third through hole penetrating the support structure layer and the polar plate layer.

[0014] The piezoelectric composite vibration layer has a second through hole, the second through hole penetrates the vibration support layer, the first electrode layer, the piezoelectric layer and the second electrode layer, and the second through hole is connected to the cavity.

[0015] The MEMS structure further has a back cavity penetrating the substrate and the barrier layer, and the second through hole is connected to the back cavity. The first electrode layer, the piezoelectric layer and the second electrode layer are suspended above the back cavity.

[0016] The MEMS structure provided in the present application combines the features of a piezoelectric MEMS microphone and a capacitive MEMS microphone. Under the condition of receiving equal sound energy, the MEMS structure obtains more converted electrical energy, thereby increasing the output electrical energy and obtaining higher sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 A three-dimensional cross-sectional view of a MEMS structure provided in Example 1 of the present invention;

[0019] Figure 2 A cross-sectional view of a MEMS structure provided in Example 1 of the present invention;

[0020] Figure 3 A three-dimensional cross-sectional view of a MEMS structure provided in Example 2 of the present invention;

[0021] Figure 4 This is a cross-sectional view of the MEMS structure provided in Example 2 of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application belong to the scope of protection of this application.

[0023] According to an embodiment of the present application, a MEMS structure is provided, which can improve sensitivity and increase output energy. The MEMS structure can be applied to sensors, such as microphones, and can also be applied to actuators, such as speakers. The MEMS structure will be described in detail below.

[0024] See also Figure 1 and Figure 2 The MEMS structure includes a back plate 13 and a piezoelectric composite vibration layer separated by a cavity 14. The back plate 13 and the piezoelectric composite vibration layer constitute a capacitor structure, wherein the piezoelectric composite vibration layer includes a vibration support layer 15, a first electrode layer 16, a piezoelectric layer 17 and a second electrode layer 18 stacked in sequence.

[0025] It can be seen that the piezoelectric composite vibration layer vibrates under the action of sound waves, and converts sound energy into electrical energy based on the piezoelectric effect. Further, the piezoelectric composite vibration layer is used as the diaphragm of the capacitor. At this time, the piezoelectric composite vibration layer and the back plate 13 form a flat capacitor. The vibration of the piezoelectric composite vibration layer causes the capacitor to change, thereby further converting sound energy into electrical energy. Therefore, the MEMS structure combines the structures of the piezoelectric MEMS microphone and the capacitive MEMS microphone. Under the condition of receiving equal sound energy, the MEMS structure obtains more converted electrical energy, thereby increasing the output electrical energy and obtaining a higher sensitivity.

[0026] Based on the different positions of the back plate 13 and the piezoelectric composite vibration layer relative to the cavity 14 , the present application provides two embodiments of the MEMS structure.

[0027] Example 1

[0028] The substrate 10 includes silicon or any suitable silicon-based compound or derivative (eg, silicon wafer, SOI, SiO 2A passivation layer 11 is formed on the substrate 10, and the material of the passivation layer 11 includes silicon dioxide and silicon nitride. A back plate 13 is formed on the passivation layer 11. A first spacer layer 12 is formed on the passivation layer 11 and is separated from the back plate 13, and the material of the first spacer layer 12 includes silicon dioxide or PSG (phospho-silicate Glass).

[0029] The vibration support layer 15 is formed on the first spacer layer 12 and is suspended above the cavity 14. The material of the vibration support layer 15 includes silicon nitride (Si 3 N 4 ), a single-layer or multi-layer composite film structure composed of silicon oxide, single crystal silicon, polycrystalline silicon or other suitable supporting materials. The first electrode layer 16 is formed above the vibration supporting layer 15, the piezoelectric layer 17 is formed above the first electrode layer 16, and the second electrode layer 18 is formed above the piezoelectric layer 17. The first piezoelectric layer 17 can convert the applied pressure into voltage, and the first electrode layer 16 and the second electrode layer 18 can transmit the generated voltage to other integrated circuit devices. The piezoelectric layer 17 includes zinc oxide, aluminum nitride, an organic piezoelectric film, lead zirconate titanate (PZT), a perovskite piezoelectric film or other suitable materials. The materials of the back plate 13, the first electrode layer 16 and the second electrode layer 18 include aluminum, gold, platinum, molybdenum, titanium, chromium, and composite films composed of them or other suitable materials.

[0030] Based on the above description, it can be known that the back plate 13 is formed above the substrate 10 , the cavity 14 is formed above the back plate 13 , and the piezoelectric composite vibration layer is formed above the cavity 14 .

[0031] Preferably, in Embodiment 1, the piezoelectric composite vibration layer has a first through hole 19, the first through hole 19 penetrates the vibration support layer 15, the first electrode layer 16, the piezoelectric layer 17 and the second electrode layer 18, and the first through hole 19 is connected to the cavity 14. The first through hole 19 is used to maintain the air pressure balance between the cavity 14 and the outside.

[0032] The piezoelectric and capacitive MEMS structure includes a group of electrical signals output by a flat plate capacitor and a group of electrical signals output by a piezoelectric composite vibration layer, thereby improving the sensitivity of the MEMS structure.

[0033] Example 2

[0034] It is worth noting that the same components are labeled the same in Example 2 and Example 1, and the materials used are also basically the same, which will not be repeated here.

[0035] See also Figure 3 and Figure 4, the MEMS structure includes a barrier layer 21 formed on a substrate 10. The material of the barrier layer 21 includes thermally oxidized silicon dioxide.

[0036] The MEMS structure further includes a vibration support layer 15 , a first electrode layer 16 , a piezoelectric layer 17 , and a second electrode layer 18 which are sequentially formed on the barrier layer 21 .

[0037] The second spacer layer 24 is formed on the barrier layer 21 and is separated from the first electrode layer 16. The material of the second spacer layer 24 may be the same as that of the first spacer layer 12. The back plate 13 is formed on the second spacer layer 24.

[0038] It can be seen from the above description that the piezoelectric composite vibration layer is formed above the substrate 10 , the cavity 14 is formed above the piezoelectric composite vibration layer, and the back plate 13 is formed above the cavity 14 .

[0039] Preferably, the back plate 13 includes a support structure layer 131 and a plate layer 132 above the support structure layer 131. The material of the plate layer 132 may be the same as that of the first electrode layer 16. The back plate 13 has a third through hole 23 penetrating the support structure layer 131 and the plate layer 132. The third through hole 23 is used to balance the air pressure and release the stress on the back plate 13.

[0040] Preferably, the piezoelectric composite vibration layer has a second through hole 19, which penetrates the vibration support layer 15, the first electrode layer 16, the piezoelectric layer 17 and the second electrode layer 18, and is connected to the cavity 14. The second through hole 19 is used to balance the air pressure and release the stress of the piezoelectric composite vibration layer.

[0041] The MEMS structure further has a back cavity 22 penetrating the substrate 10 and the barrier layer 21, and the second through hole 19 is connected to the back cavity 22. The first electrode layer 16, the piezoelectric layer 17 and the second electrode layer 18 are suspended above the back cavity 22.

[0042] In summary, with the help of the above-mentioned technical solution of the present application, the MEMS structure provided by the present application combines the characteristics of a piezoelectric MEMS microphone and a capacitive MEMS microphone. Under the condition of receiving equal sound energy, the MEMS structure obtains more converted electrical energy, thereby increasing the output electrical energy and obtaining higher sensitivity.

[0043] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A MEMS structure, characterized in that: It includes a back plate and a piezoelectric composite vibration layer separated by a cavity, the back plate and the piezoelectric composite vibration layer form a capacitor structure, wherein the piezoelectric composite vibration layer includes a vibration support layer, a first electrode layer, a piezoelectric layer and a second electrode layer stacked in sequence; Wherein, the MEMS structure includes a group of electrical signals output by the capacitor structure and a group of electrical signals output by the piezoelectric composite vibration layer; The back plate is formed above the substrate, the cavity is formed above the back plate, and the piezoelectric composite vibration layer is formed above the cavity; or, the piezoelectric composite vibration layer is formed above the substrate, the cavity is formed above the piezoelectric composite vibration layer, and the back plate is formed above the cavity.

2. The MEMS structure according to claim 1, characterized in that: The back plate is formed above the substrate, the cavity is formed above the back plate, and the piezoelectric composite vibration layer is formed above the cavity; The MEMS structure includes the substrate, a passivation layer formed over the substrate, the back plate formed over the passivation layer, a first spacer layer formed over the passivation layer and separated from the back plate, and the vibration support layer formed over the first spacer layer.

3. The MEMS structure according to claim 2, characterized in that: The piezoelectric composite vibration layer has a first through hole, the first through hole penetrates the vibration support layer, the first electrode layer, the piezoelectric layer and the second electrode layer, and the first through hole is connected to the cavity.

4. The MEMS structure according to claim 1, characterized in that: The piezoelectric composite vibration layer is formed above the substrate, the cavity is formed above the piezoelectric composite vibration layer, and the back plate is formed above the cavity; The MEMS structure includes a barrier layer formed above the substrate, the vibration support layer, the first electrode layer, the piezoelectric layer and the second electrode layer formed in sequence above the barrier layer, a second spacer layer formed above the barrier layer and separated from the first electrode layer, and a back plate formed above the second spacer layer.

5. The MEMS structure according to claim 4, characterized in that: The back plate includes a support structure layer and a plate layer above the support structure layer.

6. The MEMS structure according to claim 5, characterized in that: The back plate has a third through hole penetrating the support structure layer and the polar plate layer.

7. The MEMS structure according to claim 6, characterized in that: The piezoelectric composite vibration layer has a second through hole, the second through hole penetrates the vibration support layer, the first electrode layer, the piezoelectric layer and the second electrode layer, and the second through hole is connected to the cavity.

8. The MEMS structure according to claim 7, characterized in that: The MEMS structure also has a back cavity penetrating the substrate and the barrier layer, and the second through hole is connected to the back cavity. The first electrode layer, the piezoelectric layer and the second electrode layer are suspended above the back cavity.

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