A MEMS structure and manufacturing method thereof

Abstract

The present application discloses a MEMS structure, comprising: a substrate having a cavity; a piezoelectric composite vibration layer formed above the substrate and covering the cavity, wherein the piezoelectric composite vibration layer above the cavity has a gap, the gap extends from the upper surface of the piezoelectric composite vibration layer to the lower surface of the piezoelectric composite vibration layer, and the gap is connected to the cavity, and the gap divides the piezoelectric composite vibration layer into a peripheral cantilever beam membrane and a central diaphragm. The present application improves the sensitivity and reliability of the MEMS structure. In addition, the present application also provides a method for manufacturing the MEMS structure.

Description

Technical Field

[0001] The present invention relates to the field of micro-mechanical technology, and more specifically, to a MEMS

[0002] (Micro-Electro-Mechanical System, i.e. micro-electro-mechanical system) structure and its manufacturing method. Background Art

[0003] Piezoelectric microphones have many advantages over traditional capacitive MEMS microphones, including dustproofness, waterproofness, and higher maximum output sound pressure (AOP). Limited by the sputtering growth process of the piezoelectric film layer, the stress of the piezoelectric film layer is large and unevenly distributed, and there is a large gradient stress along the thickness direction of the piezoelectric film layer. The existence of these stresses and gradient stresses means that no matter whether the piezoelectric composite vibration layer is fixed around or partially fixed in the piezoelectric composite vibration layer, the warping and deformation of the diaphragm cannot be avoided. Deformation and warping will also affect the reliability and sensitivity of the piezoelectric microphone.

[0004] Currently, no effective solution has been proposed to address the problems of low reliability and low sensitivity of piezoelectric MEMS microphones in related technologies. Summary of the invention

[0005] In view of the problems of low reliability and low sensitivity of piezoelectric MEMS microphones in related technologies, the present application proposes a MEMS structure that can improve reliability and sensitivity.

[0006] The technical solution of this application is implemented as follows:

[0007] According to one aspect of the present application, a MEMS structure is provided, comprising:

[0008] a substrate having a cavity;

[0009] A piezoelectric composite vibration layer is formed above the substrate and covers the cavity, wherein the piezoelectric composite vibration layer above the cavity has a gap, the gap extends from the upper surface of the piezoelectric composite vibration layer to the lower surface of the piezoelectric composite vibration layer, and the gap is connected to the cavity, and the gap divides the piezoelectric composite vibration layer into an outer cantilever beam membrane and a central vibration membrane.

[0010] Wherein, the piezoelectric composite vibration layer comprises:

[0011] a support layer formed above the substrate and covering the cavity;

[0012] A first electrode layer formed on the support layer;

[0013] a first piezoelectric layer formed above the first electrode layer;

[0014] A second electrode layer is formed on the first piezoelectric layer,

[0015] Wherein, the gap extends from the upper surface of the second electrode layer to the lower surface of the support layer.

[0016] The diaphragm is fixed on the substrate via evenly arranged support angles.

[0017] Wherein, the cantilever beam membranes are evenly spaced and arranged, and the cantilever beam membranes are fan-shaped.

[0018] Wherein, the cantilever beam membranes are arranged at even intervals, and the cantilever beam membranes are in the shape of an arc, an ellipse, a triangle or other polygons.

[0019] On the other hand, the present application also provides a method for manufacturing a MEMS structure, comprising:

[0020] providing a substrate;

[0021] forming a support layer, a first electrode layer, a first piezoelectric layer, and a second electrode layer in sequence above the substrate, and forming a gap extending from an upper surface of the second electrode layer to a lower surface of the support layer;

[0022] The substrate is etched from a bottom of the substrate to form a cavity, and the cavity communicates with the gap.

[0023] Wherein, before forming the support layer, an etching stop layer is formed above the substrate, and the etching stop layer is removed after forming the cavity.

[0024] Based on this MEMS structure, by setting a gap on the piezoelectric composite vibration layer, a cantilever beam membrane on the periphery and a diaphragm in the center are formed, thereby reducing the influence of deformation and warping on the reliability and sensitivity of the MEMS structure. The cantilever beam membrane and the diaphragm form a higher voltage, thereby improving the sensitivity of the MEMS structure and improving the reliability of the MEMS structure. In addition, the present application also provides a method for manufacturing the MEMS structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] 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.

[0026] Figure 1 shows a perspective view of a MEMS structure according to some embodiments;

[0027] Figure 2 yes Figure 1 A cross-sectional perspective view of a MEMS structure;

[0028] Figure 3 yes Figure 1 A top view of the MEMS structure;

[0029] Figure 4 shows a perspective view of a MEMS structure according to some embodiments;

[0030] Figure 5 yes Figure 4 A top view of the MEMS structure;

[0031] Figures 6 to 12 is a cross-sectional view of an intermediate stage in the fabrication of a MEMS structure. DETAILED DESCRIPTION

[0032] 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.

[0033] According to an embodiment of the present application, a MEMS structure is provided, and the MEMS structure is used for sensors such as microphones or other actuators. The MEMS structure will be described in detail below.

[0034] See also Figure 1 , Figure 2 and Figure 3 The MEMS structure includes a substrate 10 having a cavity 11, and the substrate 10 includes silicon or any suitable silicon-based compound or derivative (eg, silicon wafer, SOI, polysilicon on SiO2 / Si).

[0035] The piezoelectric composite vibration layer is formed on the substrate 10 and covers the cavity 11. The piezoelectric composite vibration layer above the cavity 11 has a gap 26, which extends from the upper surface of the piezoelectric composite vibration layer to the lower surface of the piezoelectric composite vibration layer, and the gap 26 divides the piezoelectric composite vibration layer into a peripheral cantilever beam membrane 30 and a central diaphragm 40.

[0036] The diaphragm 40 is fixed on the substrate 10 via evenly arranged support angles. In some embodiments, the cantilever beam membranes 30 are evenly spaced and are fan-shaped (e.g. Figure 3 In some embodiments, the cantilever beam membranes 30 are evenly spaced and arranged, and the cantilever beam membranes 30 are in an arc shape (as shown in FIG. Figure 4As shown in the figure), ellipse, triangle or other polygon. And the number of cantilever beam membranes 30 is at least one or more. The fixed end of the cantilever beam membrane 30 is connected to the substrate 10, and the free end is suspended above the cavity 11.

[0037] Based on this MEMS structure, a gap 26 is set on the piezoelectric composite vibration layer to form an outer cantilever beam membrane 30 and a central diaphragm 40, thereby reducing the influence of deformation and warping on the reliability and sensitivity of the MEMS structure. The cantilever beam membrane 30 and the diaphragm 40 form a higher voltage, thereby improving the sensitivity of the MEMS structure and improving the reliability of the MEMS structure.

[0038] In an embodiment where the piezoelectric composite vibration layer is a single crystal, the piezoelectric composite vibration layer includes a vibration support layer 21, a first electrode layer 22, a first piezoelectric layer 23, and a second electrode layer 24. The vibration support layer 21 is formed above the substrate 10 and covers the cavity 11. The first electrode layer 22 is formed above the vibration support layer 21. The first piezoelectric layer 23 is formed above the first electrode layer 22. The second electrode layer 24 is formed above the first piezoelectric layer 23. In other words, the gap 26 extends from the upper surface of the second electrode layer to the lower surface of the support layer, so that the gap 26 is connected to the cavity 11. The first piezoelectric layer 23 can convert the applied pressure into voltage, and the first electrode layer 22 and the second electrode layer 24 can transmit the generated voltage to other integrated circuit devices. In addition, the piezoelectric composite vibration layer can also be a dual crystal structure, in which case the piezoelectric composite vibration layer may include a third electrode layer, a second piezoelectric layer, a fourth electrode layer, a third piezoelectric layer, and a fifth electrode layer stacked sequentially from bottom to top. The piezoelectric composite vibration layer of the dual crystal structure also achieves the effect of converting acoustic energy into electrical energy.

[0039] In some embodiments, the piezoelectric composite vibration layer further includes an etch stop layer 25, which is formed between the vibration support layer 21 and the substrate 10. The etch stop layer 25 may also be removed.

[0040] In some embodiments, the vibration support layer 21 includes a single layer or multilayer composite film structure composed of silicon nitride (Si3N4), silicon oxide, single crystal silicon, polycrystalline silicon, or other suitable supporting materials. The first piezoelectric layer 23 includes zinc oxide, aluminum nitride, organic piezoelectric film, lead zirconate titanate (PZT), perovskite piezoelectric film, or other suitable materials. The first electrode layer 22 and the second electrode layer 24 include aluminum, gold, platinum, molybdenum, titanium, chromium, and composite films composed thereof, or other suitable materials.

[0041] In summary, the present application provides a MEMS structure, in which a gap 26 is set on the piezoelectric composite vibration layer to form an outer cantilever beam membrane 30 and a diaphragm 40, thereby reducing the influence of deformation and warping on the reliability and sensitivity of the MEMS structure. The cantilever beam membrane 30 and the diaphragm 40 form a higher voltage, thereby improving the sensitivity of the MEMS structure and improving the reliability of the MEMS structure.

[0042] On the other hand, the present application also provides a manufacturing method for forming the above-mentioned MEMS structure, the process is as follows:

[0043] See also Figure 6 , step S1, providing a substrate 10.

[0044] Step S2, forming an etch stop layer 25 on the substrate 10, wherein the material of the etch stop layer 25 includes silicon oxide. The etch stop layer 25 may be formed by thermal oxidation or PECVD (Plasma Enhanced Chemical Vapor Deposition). In other embodiments, step S2 may be skipped or omitted.

[0045] See also Figure 7 , Figure 8 , step S3 , forming a vibration support layer 21 , a first electrode layer 22 , a first piezoelectric layer 23 and a second electrode layer 24 in sequence above the etching stop layer 25 .

[0046] See also Fig. 9 In step S4 , metal pads 27 are connected to the first electrode layer 22 and the second electrode layer 24 .

[0047] See also Fig.10 , step S5 , etching to form a gap 26 extending from the upper surface of the second electrode layer 24 to the lower surface of the vibration support layer 21 .

[0048] See also Fig.11 In step S6 , the substrate 10 is etched from the bottom of the substrate 10 to form a cavity 11 , and the etching of the substrate 10 is stopped at the etching stop layer 25 .

[0049] See also Fig.12 , step S7, etching and removing the etching stop layer 25 by other means until the cavity 11 is connected with the gap 26.

[0050] Based on the above manufacturing method, the above MEMS structure is obtained. The MEMS structure has high sensitivity and reliability.

[0051] 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: include: a substrate having a cavity; a piezoelectric composite vibration layer formed above the substrate and covering the cavity, wherein the piezoelectric composite vibration layer above the cavity has a gap, the gap extending from the upper surface of the piezoelectric composite vibration layer to the lower surface of the piezoelectric composite vibration layer, and the gap is connected to the cavity, and the gap divides the piezoelectric composite vibration layer into a peripheral cantilever beam membrane and a central vibration membrane; The diaphragm is fixed on the substrate via evenly arranged support angles; the cantilever beam membranes are evenly spaced and are fan-shaped, arc-shaped, elliptical, triangular or other polygonal shapes.

2. The MEMS structure according to claim 1, wherein: The piezoelectric composite vibration layer includes: a supporting layer formed above the substrate and covering the cavity; a first electrode layer formed on the support layer; a first piezoelectric layer formed above the first electrode layer; a second electrode layer formed above the first piezoelectric layer, The gap extends from the upper surface of the second electrode layer to the lower surface of the support layer.

3. A method for manufacturing a MEMS structure, characterized in that: include: providing a substrate; forming a support layer, a first electrode layer, a first piezoelectric layer, and a second electrode layer in sequence above the substrate, and forming a gap extending from an upper surface of the second electrode layer to a lower surface of the support layer; Etching the substrate from a bottom of the substrate to form a cavity, wherein the cavity is in communication with the gap; Among them, the gap divides the piezoelectric composite vibration layer into an outer cantilever beam membrane and a central vibration membrane; the vibration membrane is fixed above the substrate through evenly arranged support angles; the cantilever beam membranes are evenly spaced, and the cantilever beam membranes are fan-shaped, arc-shaped, elliptical, triangular or other polygonal shapes.

4. The method for manufacturing a MEMS structure according to claim 3, wherein: Before forming the support layer, an etch stop layer is formed over the substrate, and the etch stop layer is removed after forming the cavity.

Images