CN111786653A - Bulk acoustic wave resonator, method of manufacturing the same, filter, and radio frequency communication system - Google Patents
Bulk acoustic wave resonator, method of manufacturing the same, filter, and radio frequency communication system Download PDFInfo
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Images
Classifications
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
- H03H9/171—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
- H03H9/172—Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume
- H03H9/174—Membranes
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/462—Microelectro-mechanical filters
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/54—Filters comprising resonators of piezo-electric or electrostrictive material
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/54—Filters comprising resonators of piezo-electric or electrostrictive material
- H03H9/547—Notch filters, e.g. notch BAW or thin film resonator filters
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H2009/155—Constructional features of resonators consisting of piezoelectric or electrostrictive material using MEMS techniques
Abstract
The invention provides a bulk acoustic wave resonator, a manufacturing method thereof, a filter and a radio frequency communication system, wherein a bottom electrode sunken part and a top electrode sunken part which are formed at the periphery of a piezoelectric resonance layer and are suspended above a cavity can prevent transverse waves generated by the piezoelectric resonance layer from being transmitted to the periphery of the cavity and reflect the transverse waves back to an effective working area, so that the acoustic wave loss is reduced, the quality factor of the resonator is improved, and the performance of a device can be improved finally. Further, the overlapping parts of the bottom electrode overlapping part and the top electrode overlapping part and the cavity are all suspended, and the bottom electrode overlapping part and the top electrode overlapping part are staggered mutually, so that parasitic parameters can be greatly reduced, the problems of electric leakage, short circuit and the like are avoided, and the reliability of the device can be improved.
Description
Technical Field
The invention relates to the technical field of radio frequency communication, in particular to a bulk acoustic wave resonator, a manufacturing method thereof, a filter and a radio frequency communication system.
Background
Radio Frequency (RF) communications, such as those used in mobile phones, require the use of RF filters, each capable of passing a desired frequency and limiting all other frequencies. With the development of mobile communication technology, the amount of mobile data transmission is also rapidly increasing. Therefore, increasing the transmission power of a wireless power transmitting device such as a wireless base station, a micro base station or a repeater becomes a problem that must be considered under the premise that the frequency resources are limited and the mobile communication device should be used as little as possible, and the requirement for the filter power in the front-end circuit of the mobile communication device is higher and higher.
At present, a high-power filter in a wireless base station and other devices is mainly a cavity filter, and the power of the high-power filter can reach hundreds of watts, but the size of the high-power filter is too large. There are also devices that use dielectric filters with average powers of up to 5 watts or more, which are also large in size. Due to the large size, these two filters cannot be integrated into the rf front-end chip.
With the more mature MEMS technology, the filter composed of Bulk Acoustic Wave (BAW) resonators can overcome the above two kinds of filter defects. The bulk acoustic wave resonator has the advantages of incomparable volume of a ceramic dielectric filter and incomparable working frequency and power capacity of a Surface Acoustic Wave (SAW) resonator, and becomes the development trend of the current wireless communication system.
The bulk acoustic wave resonator has a sandwich structure formed by a bottom electrode, a piezoelectric film and a top electrode, converts electric energy into mechanical energy by utilizing the inverse piezoelectric effect of the piezoelectric film, and forms standing waves in a filter formed by the bulk acoustic wave resonator in the form of acoustic waves. Since the speed of an acoustic wave is 5 orders of magnitude smaller than that of an electromagnetic wave, the size of a filter constituted by a bulk acoustic wave resonator is smaller than that of a conventional dielectric filter or the like.
The working principle of the cavity type bulk acoustic wave resonator is that the acoustic waves are reflected at the interface of a bottom electrode or a supporting layer and air, the acoustic waves are limited on a piezoelectric layer, resonance is achieved, and the cavity type bulk acoustic wave resonator has the advantages of being high in Q value, low in insertion loss, capable of being integrated and the like, and is widely adopted.
However, the quality factor (Q) of the currently manufactured cavity bulk acoustic wave resonator cannot be further improved, and thus the requirement of a high-performance radio frequency system cannot be met.
Disclosure of Invention
The invention aims to provide a bulk acoustic wave resonator, a manufacturing method thereof, a filter and a radio frequency communication system, which can improve the quality factor and further improve the device performance.
In order to achieve the above object, the present invention provides a bulk acoustic wave resonator comprising:
a substrate;
the bottom electrode layer is arranged on the substrate, a cavity is formed between the bottom electrode layer and the substrate, the bottom electrode layer is provided with a bottom electrode sunken part, and the bottom electrode sunken part is positioned in the area of the cavity and is sunken towards the direction close to the bottom surface of the cavity;
a piezoelectric resonance layer formed on the bottom electrode layer above the cavity;
the top electrode layer is formed on the piezoelectric resonance layer and provided with a top electrode sunken part, the top electrode sunken part is positioned in the area of the cavity and is sunken towards the direction close to the bottom surface of the cavity, and the top electrode sunken part and the bottom electrode sunken part are both positioned in the cavity area at the periphery of the piezoelectric resonance layer; the bottom electrode recess and the top electrode recess both extend around the peripheral direction of the piezoelectric resonance layer, and are at least partially opposite to each other.
The invention also provides a filter comprising at least one bulk acoustic wave resonator according to the invention.
The invention also provides a radio frequency communication system comprising at least one filter according to the invention.
The present invention also provides a method for manufacturing a bulk acoustic wave resonator, comprising:
providing a substrate, and forming a first sacrificial layer on a part of the substrate;
forming a first groove in an edge portion of the first sacrificial layer, the first groove not exposing a surface of the substrate under the first sacrificial layer;
forming a bottom electrode layer on the first sacrificial layer, wherein a bottom electrode concave part is formed on the part, covered on the surface of the first groove, of the bottom electrode layer;
forming a piezoelectric resonance layer on the bottom electrode layer, wherein the piezoelectric resonance layer exposes the bottom electrode sunken part;
forming a second sacrificial layer in the exposed area around the piezoelectric resonance layer, wherein a second groove is formed in the second sacrificial layer;
forming a top electrode layer on the piezoelectric resonance layer and a part of the second sacrificial layer around the piezoelectric resonance layer, wherein the part of the top electrode layer covering the second groove forms a top electrode concave part;
and removing the second sacrificial layer and the first sacrificial layer, forming a cavity at the position of the second sacrificial layer and the first sacrificial layer, wherein the top electrode concave part and the bottom electrode concave part are both positioned in the cavity area at the periphery of the piezoelectric resonance layer, and the bottom electrode concave part and the top electrode concave part extend around the peripheral direction of the piezoelectric resonance layer and are at least partially opposite to each other.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
1. when electric energy is applied to the bottom electrode and the top electrode, a desired longitudinal wave propagating along the thickness direction and an undesired transverse wave propagating along the plane of the piezoelectric resonance layer are generated through a piezoelectric phenomenon generated in the piezoelectric resonance layer, the transverse wave can be blocked at the bottom electrode sunken part and the top electrode sunken part suspended on the cavity at the periphery of the piezoelectric resonance layer and reflected back to the corresponding region of the piezoelectric resonance layer, and then the loss caused when the transverse wave propagates to the film at the periphery of the cavity is reduced and reduced, so that the acoustic wave loss is improved, the quality factor of the resonator is improved, and finally the device performance can be improved.
2. The periphery on piezoelectricity resonance layer and the peripheral alternate segregation of cavity, piezoelectricity resonance layer can not extend to the peripheral substrate top of cavity promptly continuously, can restrict the effective working area of bulk acoustic wave syntonizer in the cavity region completely, and bottom electrode overlap joint portion and top electrode overlap joint portion all can extend to the part edge of cavity (bottom electrode layer and top electrode layer can not cover the cavity comprehensively promptly), can reduce the influence of the longitudinal vibration that the rete produced piezoelectricity resonance layer around the cavity from this, the performance is improved.
3. Even if the bottom electrode sunken part and the top electrode sunken part have the mutually overlapped parts, a gap structure is arranged between the overlapped parts, so that parasitic parameters can be greatly reduced, the problems of electric contact and the like of the top electrode layer and the bottom electrode layer in a cavity region are avoided, and the reliability of the device can be improved.
4. Bottom electrode overlap joint portion and top electrode overlap joint portion all are unsettled with the overlap section of cavity, and bottom electrode overlap joint portion and top electrode overlap joint portion stagger each other in the region of cavity (the two does not overlap in the cavity region promptly), can greatly reduced parasitic parameter from this to avoid bottom electrode overlap joint portion and top electrode overlap joint portion to contact and the electric leakage that arouses, short circuit scheduling problem, can improve the device reliability.
5. The bottom electrode overlapping part completely covers the cavity above the cavity part where the bottom electrode overlapping part is located, so that the membrane layer above the bottom electrode overlapping part with a large area can be strongly and mechanically supported, and the problem of failure of a device due to cavity collapse is avoided.
6. The top electrode depressed part is around top electrode resonance portion a week, and bottom electrode depressed part is around bottom electrode resonance portion a week, can follow the peripheral omnidirectional of piezoelectricity resonance layer and block the transverse wave, and then obtain the quality factor of preferred.
7. Bottom electrode depressed part, bottom electrode resonance portion and bottom electrode overlap joint portion adopt same rete to form, and the membrane is thick even, top electrode depressed part, top electrode resonance portion and top electrode overlap joint portion adopt same rete to form, and the membrane is thick even, can simplify the technology from this, and the cost is reduced, and because the membrane of bottom electrode depressed part is thick basically the same with other parts of bottom electrode layer, the membrane of top electrode depressed part is thick basically the same with other parts of top electrode layer, consequently bottom electrode depressed part fracture and the cracked condition of top electrode depressed part can not appear, can improve the reliability of device.
Drawings
Fig. 1A is a schematic top view of a bulk acoustic wave resonator according to an embodiment of the present invention.
Fig. 1B and 1C are schematic sectional views along the lines XX 'and YY' in fig. 1.
Fig. 2A to 2D are schematic top-view structural diagrams of bulk acoustic wave resonators according to other embodiments of the present invention.
Fig. 2E is a schematic cross-sectional view of a bulk acoustic wave resonator according to another embodiment of the present invention.
Fig. 3 is a flowchart of a method of manufacturing a bulk acoustic wave resonator according to an embodiment of the present invention.
Fig. 4A to 4H are schematic cross-sectional views along XX' in fig. 1A in a method of manufacturing a bulk acoustic wave resonator according to an embodiment of the present invention.
Fig. 5 is a schematic sectional view taken along XX' in fig. 1A in a method of manufacturing a bulk acoustic wave resonator according to another embodiment of the present invention.
Wherein the reference numbers are as follows:
100-a substrate; 101, etching a protective layer; 102-a cavity; 102' -a third groove; 102A-active working area; 102B-null area; 103-a first sacrificial layer; 1031-first sub-sacrificial layer; 1032-a second sub-sacrificial layer; 1033-a first groove; 104-bottom electrode layer (i.e. remaining bottom electrode material layer); 1040-bottom electrode lap; 1041-bottom electrode recess; 1042-bottom electrode resonance part; 1043-a bottom electrode periphery; 105-a layer of piezoelectric material; 1050-a piezoelectric peripheral portion; 1051-a piezoelectric resonance layer (or called as a piezoelectric resonance part); 106-a second sacrificial layer; 107-a second groove; 108-top electrode layer (i.e. remaining top electrode material layer); 1080-top electrode lap; 1081-top electrode recess; 1082-a top electrode resonance section; 1083-top electrode peripheral portion.
Detailed Description
The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention. Similarly, if the method described herein comprises a series of steps, the order in which these steps are presented herein is not necessarily the only order in which these steps may be performed, and some of the described steps may be omitted and/or some other steps not described herein may be added to the method. In addition, something "offset from" something in this context means that the two do not overlap in the region of the cavity, i.e. that the projections of the two onto the bottom surface of the cavity do not overlap.
Referring to fig. 1A to fig. 1C, fig. 1A is a schematic top view structure diagram of a bulk acoustic wave resonator according to an embodiment of the present invention, fig. 1B is a schematic cross-sectional structure diagram along XX 'in fig. 1, fig. 1C is a schematic cross-sectional structure diagram along YY' in fig. 1A, and the bulk acoustic wave resonator of the present embodiment includes: a substrate, a bottom electrode layer 104, a piezoelectric resonance layer 1051, and a top electrode layer 108.
The substrate comprises a base 100 and an etching protection layer 101 covering the base 100. The substrate 100 may be any suitable substrate known to those skilled in the art, and may be, for example, at least one of the following materials: silicon (Si), germanium (Ge), silicon germanium (SiGe), silicon carbon (SiC), silicon germanium carbon (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP), or other III/V compound semiconductors, and further includes a multilayer structure composed of these semiconductors, or may be Silicon On Insulator (SOI), silicon on insulator (SSOI), silicon germanium on insulator (S-SiGeOI), silicon germanium on insulator (SiGeOI), and germanium on insulator (GeOI), or may be Double-side polished silicon Wafers (DSP), or may be a ceramic substrate such as alumina, quartz, or a glass substrate. The material of the etching protection layer 101 may be any suitable dielectric material, including but not limited to at least one of silicon oxide, silicon nitride, silicon oxynitride, silicon carbonitride, and the like, and the etching protection layer may be used to increase the structural stability of the finally manufactured bulk acoustic wave resonator, increase the isolation between the bulk acoustic wave resonator and the substrate 100, and reduce the resistivity requirement on the substrate 100, and on the other hand, protect other regions of the substrate from being etched in the process of manufacturing the bulk acoustic wave resonator, thereby improving the performance and reliability of the device.
A cavity 102 is formed between the bottom electrode layer 104 and the substrate. Referring to fig. 1A to fig. 1C, in the present embodiment, the cavity 102 may be formed by sequentially etching the etching protection layer 101 and the base 100 with a partial thickness through an etching process, so as to form a groove structure with a whole bottom recessed in the substrate. However, the technology of the present invention is not limited thereto, and referring to fig. 2E, in another embodiment of the present invention, the cavity 102 may also be formed above the top surface of the etching protection layer 101 by a process of removing a sacrificial layer protruding from the surface of the etching protection layer 101 by a post-removal method, so as to form a cavity structure protruding from the surface of the etching protection layer 101. In addition, in the present embodiment, the bottom surface of the cavity 102 is rectangular, but in other embodiments of the present invention, the bottom surface of the cavity 102 may also be circular, oval, or polygonal other than rectangular, such as pentagonal, hexagonal, etc.
The piezoelectric resonance layer 1051, which may be referred to as a piezoelectric resonance portion, is located in an upper region of the cavity 102 (which may be said to be located in a region of the cavity 102) corresponding to an effective operating region of the bulk acoustic wave resonator, and the piezoelectric resonance layer 1051 is provided between the bottom electrode layer 104 and the top electrode layer 108. The bottom electrode layer 104 comprises a bottom electrode lap 1040, a bottom electrode recess 1041 and a bottom electrode resonance portion 1042 which are sequentially connected, the top electrode layer 108 comprises a top electrode lap 1080, a top electrode recess 1081 and a top electrode resonance portion 1082 which are sequentially connected, the bottom electrode resonance portion 1042 and the top electrode resonance portion 1082 are both overlapped with the piezoelectric resonance layer 1051, the cavity 102 and the area corresponding to the overlapped bottom electrode resonance portion 1042, piezoelectric resonance layer 1051 and top electrode resonance portion 1082 form an effective working area 102A of the bulk acoustic wave resonator, the part of the cavity 102 except the effective working area 102A is an ineffective area 102B, the piezoelectric resonance layer 1051 is located in the effective working area 102A and separated from the film layers around the cavity 102, the effective working area of the bulk acoustic wave resonator can be completely limited in the area of the cavity 102, and the influence of the film layers around the cavity on the longitudinal vibration generated by the piezoelectric resonance layer can be reduced, the parasitic parameters generated in the inactive region 102B are reduced, and the device performance is improved. The bottom electrode resonance portion 1042, the piezoelectric resonance layer 1051, and the top electrode resonance portion 1082 are flat structures whose upper and lower surfaces are planar, the bottom electrode recess 1041 is located above the cavity 102B at the periphery of the active working area 102A, electrically connected to the bottom electrode resonance portion 1042, and recessed toward the direction close to the bottom surface of the cavity, and the top electrode recess 1081 is located above the cavity 102B at the periphery of the active working area 102A, electrically connected to the top electrode resonance portion 1082, and recessed toward the direction close to the bottom surface of the cavity 102. The bottom electrode recessed portion 1041 is lower than the top surface of the bottom electrode resonance portion 1042 as a whole, the top electrode recessed portion 1081 is lower than the top surface of the top electrode resonance portion 1082 as a whole, and both the top electrode recessed portion 1081 and the bottom electrode recessed portion 1041 are located in a cavity region (i.e., 102B) in the periphery of the piezoelectric resonance layer 1051. The bottom electrode recess 1041 and the top electrode recess 1081 may be solid structures, or may be hollow structures, preferably hollow structures, so that the film thicknesses of the bottom electrode layer 104 and the top electrode layer 108 are uniform, the bottom electrode resonance portion 1042 and the piezoelectric resonance layer 1051 are prevented from being separated by gravity of the solid bottom electrode recess 1041, and the top electrode resonance portion 1082 and the piezoelectric resonance layer 1051 and the bottom electrode resonance portion 1042 below the top electrode resonance portion are prevented from being deformed by the solid top electrode recess 1081, thereby further improving the resonance factor. The bottom electrode resonance part 1042 and the top electrode resonance part 1082 are polygonal (both top and bottom surfaces are polygonal), and the shapes of the bottom electrode resonance part 1042 and the top electrode resonance part 1082 may be similar (as shown in fig. 2A to 2B and 2D) or identical (as shown in fig. 1A and 2C). The piezoelectric resonance layer 1051 has a polygonal structure similar to the shapes of the bottom electrode resonance portion 1042 and the top electrode resonance portion 1082.
Referring to fig. 1A to 1C, in the present embodiment, the bottom electrode layer 104, the piezoelectric resonance layer 1051 and the top electrode layer 108 form a film structure in a shape of a "watch"; one corner of the bottom electrode strap 1040 and the bottom electrode resonance portion 1042 is aligned, one corner of the top electrode strap 1080 and the top electrode resonance portion 1082 is aligned, and the bottom electrode strap 1040 and the top electrode strap 1080 correspond to two bands of a "watch"; the bottom electrode recessed portion 1041 is disposed along the side of the bottom electrode resonance portion 1042 and is only disposed in the region where the bottom electrode lap 1040 and the bottom electrode resonance portion 1042 are aligned, the top electrode recessed portion 1081 is disposed along the side of the top electrode resonance portion 1082 and is only disposed in the region where the top electrode lap 1080 and the top electrode resonance portion 1082 are aligned, and the bottom electrode recessed portion 1041 and the top electrode recessed portion 1081 correspond to a connection structure between a dial and two wristbands of a "wristwatch"; the stacked structure of the bottom electrode resonance portion 1042, the piezoelectric resonance layer 1051, and the top electrode resonance portion 1082 in the active area 102A corresponds to a dial of a "wristwatch", which is separated from a film layer on a substrate around the cavity 102 by the cavity 102 except for a portion of the band that is in contact with the film layer on the substrate around the cavity 102. That is, in this embodiment, the bottom electrode recess 1041 and the top electrode recess 1081 both extend around the peripheral direction of the piezoelectric resonance layer 1051, and the bottom electrode recess 1041 and the top electrode recess 1081 surround only a part of the edges of the piezoelectric resonance layer 1051 in the peripheral direction of the piezoelectric resonance layer 1051, and with reference to the plane of the piezoelectric resonance layer 1051, the top electrode recess 1081 and the bottom electrode recess 1041 are completely opposite to each other and are disposed at two sides of the piezoelectric resonance layer 1051, thereby, while achieving a certain effect of blocking transverse waves, it is possible to facilitate reduction in the area of the inactive region 102B not covered by the top electrode strap 1080 and the bottom electrode strap 1040, and then be favorable to the reduction of device size, still be favorable to reducing the area of top electrode overlap joint portion 1080 and bottom electrode overlap joint portion 1040 simultaneously to further reduce parasitic parameter, improve the electrical property of device. The bottom electrode overlapping portion 1040 is electrically connected to a side of the bottom electrode recessed portion 1041 facing away from the bottom electrode resonance portion 1042, and extends from the bottom electrode recessed portion 1041 to a portion of the etching protection layer 101 at the periphery of the cavity 102 after suspending above the cavity (i.e., 102B) at the outer side of the bottom electrode recessed portion 1041; the top electrode bonding portion 1080 is electrically connected to one side of the top electrode recess 1081, which faces away from the top electrode resonance portion 1082, and extends from the top electrode recess 1081 to a position above a part of the etching protection layer 101 on the periphery of the cavity 102 after being suspended above the cavity (i.e., 102B) outside the top electrode recess 1081; the bottom electrode overlapping portion 1040 and the top electrode overlapping portion 1080 extend to the upper side of the substrate outside two opposite sides of the cavity 102, and at this time, the bottom electrode overlapping portion 1040 and the top electrode overlapping portion 1080 are staggered with each other (that is, the two are not overlapped) in the cavity 102 region, so that parasitic parameters can be reduced, the problems of electric leakage, short circuit and the like caused by the contact of the bottom electrode overlapping portion and the top electrode overlapping portion are avoided, and the device performance is improved. The bottom electrode strap 1040 may be configured to connect to a corresponding signal line, so as to transmit a corresponding signal to the bottom electrode resonance portion 1042 through the bottom electrode recess 1041, and the top electrode strap 1080 may be configured to connect to a corresponding signal line, so as to transmit a corresponding signal to the top electrode resonance portion 1082 through the top electrode recess 1081, so that the bulk acoustic wave resonator may operate normally, specifically, a time-varying voltage is applied to the bottom electrode resonance portion 1042 and the top electrode resonance portion 1082 through the bottom electrode strap 1040 and the top electrode strap 1080, so as to excite a longitudinally extending mode or a "piston" mode, the piezoelectric resonance layer 1051 converts energy in the form of electrical energy into a longitudinal wave, in the process, a parasitic transverse wave may be generated, and the bottom electrode recess 1041 and the top electrode recess 1081 may block the transverse wave from propagating into a film layer on the periphery of the cavity, so as to be limited in the area of the cavity 102, thereby avoiding energy loss caused by transverse waves and improving quality factors.
Preferably, the line widths of the top electrode recess 1081 and the bottom electrode recess 1041 are respectively the minimum line widths allowed by the corresponding processes, and the horizontal distance between the bottom electrode recess 1041 and the piezoelectric resonance layer 1051 and the horizontal distance between the top electrode recess 1081 and the piezoelectric resonance layer 1051 are the minimum distances allowed by the corresponding processes, so that the top electrode recess 1081 and the bottom electrode recess 1041 can achieve a certain effect of blocking transverse waves, and at the same time, can be beneficial to reducing the device area.
In addition, the side wall of the top electrode recess 1081 is an inclined side wall relative to the top surface of the piezoelectric resonance layer, as shown in fig. 1B, the cross section of the top electrode recess 1081 along the line XX' in fig. 1A is trapezoidal or trapezoid-like, and the included angles β 1 and β 2 between the two side walls of the top electrode recess 1081 and the top surface of the piezoelectric resonance layer 1051 are both less than or equal to 45 degrees, so that the top electrode recess 1081 is prevented from being broken due to the excessively vertical side wall of the top electrode recess 1081, the effect of transmitting signals to the top electrode resonance portion 1082 is further influenced, and meanwhile, the thickness uniformity of the entire top electrode layer 108 can be improved; the side wall of the bottom electrode recess 1041 is an inclined side wall relative to the bottom surface of the piezoelectric resonance layer, as shown in fig. 1B, the cross section of the bottom electrode recess 1041 along the line XX' in fig. 1A is trapezoidal or trapezoid-like, and included angles α 1 and α 2 between the two side walls of the bottom electrode recess 1041 and the bottom surface of the piezoelectric resonance layer 1051 are both less than or equal to 45 degrees, so that the bottom electrode layer 104 is prevented from being broken due to the fact that the side wall of the bottom electrode recess 1041 is too vertical, the effect of transmitting signals to the bottom electrode resonance portion 1042 is further influenced, and meanwhile, the thickness uniformity of the bottom electrode layer 104 can be improved.
In a preferred embodiment of the present invention, the bottom electrode resonance portion 1042, the bottom electrode recess 1041 and the bottom electrode overlapping portion 1040 are formed by a same film layer manufacturing process (i.e. a same film layer manufacturing process), the top electrode resonance portion 1082, the top electrode recess 1081 and the top electrode overlapping portion 1080 are formed by a same film layer manufacturing process (i.e. a same film layer manufacturing process), i.e. the bottom electrode resonance portion 1042, the bottom electrode recess 1041 and the bottom electrode overlapping portion 1040 are integrally formed, and the top electrode resonance portion 1082, the top electrode recess 1081 and the top electrode overlapping portion 1080 are integrally formed, so that the process can be simplified and the cost can be reduced, wherein the film layer materials for manufacturing the bottom electrode resonance portion 1042, the bottom electrode recess 1041 and the bottom electrode overlapping portion 1040 and the film layer materials for manufacturing the top electrode resonance portion 1082, the top electrode recess 1081 and the top electrode overlapping portion 1080 can respectively use any suitable conductive material or any suitable conductive material known in the art The semiconductor material may be a metal material having a conductive property, such as one or more of aluminum (Al), copper (Cu), platinum (Pt), gold (Au), molybdenum (Mo), tungsten (W), iridium (Ir), osmium (Os), rhenium (Re), palladium (Pd), rhodium (Rh), and ruthenium (Ru). Of course, in other embodiments of the present invention, under the premise of process cost and process technology, the bottom electrode resonance portion 1042, the bottom electrode recess 1041 and the bottom electrode bonding portion 1040 may also be formed by different film layer manufacturing processes, and the top electrode resonance portion 1082, the top electrode recess 1081 and the top electrode bonding portion 1080 may be formed by different film layer manufacturing processes.
Referring to fig. 2A to 2D, in order to further improve the transverse wave blocking effect, the bottom electrode depression portion 1041 extends to more continuous sides of the bottom electrode resonance portion 1042, the top electrode depression portion 1081 extends to more continuous sides of the top electrode resonance portion 1082, and when the top electrode depression portion 1081 and the bottom electrode depression portion 1041 are overlapped in the vertical direction, there is a gap between the top electrode depression portion 1081 and the bottom electrode depression portion 1041 in the vertical direction without interlayer contact. For example, referring to fig. 2A, the projections of the bottom electrode recess 1041 and the top electrode recess 1081 onto the bottom surface of the cavity 102 may be directly or nearly identical, i.e. the projections of the bottom electrode recess 1041 and the top electrode recess 1081 onto the bottom surface of the cavity 102 may constitute a completely closed ring or a nearly closed ring, thus, the bottom electrode recess 1041 and the top electrode recess 1081 cooperate to block transverse waves around the entire periphery of the piezoelectric resonance layer 1051, in this case, the projection sizes of the bottom electrode recess 1041 and the top electrode recess 1081 on the bottom surface of the cavity 102 may be equal to the combined ring (in this case, the bottom electrode recess 1041 and the top electrode recess 1081 are respectively disposed on both sides of the piezoelectric resonance layer 1051, and all the portions are completely opposite to each other), or may be unequal (in this case, the bottom electrode recess 1041 and the top electrode recess 1081 are respectively disposed on both sides of the piezoelectric resonance layer 1051, and only some of the portions are opposite to each other). For another example, referring to fig. 2B, the piezoelectric resonance layer 1051, the top electrode resonance portion 1082 and the bottom electrode resonance portion 1042 are all pentagonal planar structures, the area of the piezoelectric resonance layer 1051 is the smallest, the area of the top electrode resonance portion 1082 is the second, and the area of the bottom electrode resonance portion 1042 is the largest, the bottom electrode recess portion 1041 is disposed along and connected to each side of the bottom electrode resonance portion 1042, and the projection of the bottom electrode recess portion 1041 on the bottom surface of the cavity 102 exposes a partial projection or a full projection of the boundary of the top electrode recess portion 1081 connected by the top electrode bridging portion 1080 on the bottom surface of the cavity 102, the top electrode recess portion 1081 is disposed along and connected to each side of the top electrode resonance portion 1082, and the projection of the top electrode recess portion 1081 on the bottom surface of the cavity 102 exposes a partial projection or a full projection of the boundary of the bottom electrode recess portion 1041 connected by the bottom electrode bridging portion 1040 on the bottom surface of the cavity 102, therefore, the bottom electrode recessed portion 1041 and the top electrode overlapping portion 1080 are not overlapped, and the top electrode recessed portion 1081 and the bottom electrode overlapping portion 1040 are not overlapped, so as to reduce parasitic parameters, and in addition, the bottom electrode recessed portion 1041 and the top electrode recessed portion 1081 can be staggered with each other by some amount or even completely, that is, at this time, the bottom electrode recessed portion 1041 and the top electrode recessed portion 1081 are partially aligned up and down (or called as overlapping) or completely staggered in a direction perpendicular to the piezoelectric resonance layer 1051, but all the portions are opposite in a peripheral direction of the piezoelectric resonance layer 1051, so that in a projection structure onto the bottom surface of the cavity 102, the bottom electrode recessed portion 1041 can partially surround the top electrode recessed portion 1081, in this way, not only the cooperation of the bottom electrode recessed portion 1041 and the top electrode recessed portion 1081 can block transverse waves of the whole periphery of the piezoelectric resonance layer 1051, but also can reduce the alignment requirements of the bottom electrode recessed portion 1041 and the top electrode recessed portion 1081, is beneficial to reducing the difficulty of the process manufacture. For another example, referring to fig. 2C, the piezoelectric resonant layer 1051, the top electrode resonant portion 1082, and the bottom electrode resonant portion 1042 are all pentagonal planar structures, and the area of the piezoelectric resonant layer 1051 is the smallest, the areas, shapes, etc. of the top electrode resonant portion 1082 and the bottom electrode resonant portion 1042 are the same or substantially the same, the bottom electrode recess 1041 surrounds a circumference of the bottom electrode resonant portion 1042, the top electrode recess 1081 surrounds a circumference of the top electrode resonant portion 1082, and the projections of the bottom electrode recess 1041 and the top electrode recess 1081 on the bottom surface of the cavity 102 are overlapped, and the projections of the top electrode resonant portion 1082 and the bottom electrode resonant portion 1042 on the bottom surface of the cavity 102 are overlapped, so that the bottom electrode recess 1041 and the top electrode recess 1081 located at different heights in the vertical direction are all in a closed loop shape, thereby blocking transverse waves generated by the piezoelectric resonant layer 1051 at different heights. That is, when the bottom electrode recess 1041 extends to more continuous sides of the bottom electrode resonance portion 1042, the top electrode recess 1081 extends to more continuous sides of the top electrode resonance portion 1082, the bottom electrode recess 1041 and the top electrode recess 1081 each extend around the peripheral direction of the piezoelectric resonance layer 1051, and the bottom electrode recess 1041 and the top electrode recess 1081 partially surround the periphery of the piezoelectric resonance layer 1051 in the peripheral direction of the piezoelectric resonance layer 1051, respectively (as shown in fig. 2A-2B), at this time, the top electrode recess 1081 and the bottom electrode recess 1041 are both at least partially opposed, alternatively, the bottom electrode recess 1041 and the top electrode recess 1081 may surround the piezoelectric resonance layer 1051 by one turn in the peripheral direction of the piezoelectric resonance layer 1051, respectively (as shown in fig. 2C), and at this time, all portions of the top electrode recess 1081 and the bottom electrode recess 1041 are opposite.
Referring to fig. 2A to 2D, in the embodiments of the present invention, the bottom electrode bonding portion 1040 is electrically connected to at least one edge or at least one corner of the bottom electrode recess 1041 facing away from the bottom electrode resonance portion 1042, and extends from the corresponding edge of the bottom electrode recess 1041 to above a portion of the etching protection layer 101 at the periphery of the cavity 102 after suspending above the cavity (i.e., 102B) outside the bottom electrode recess 1041; the top electrode bonding portion 1080 is electrically connected to at least one edge or at least one corner of the top electrode recess 1081 facing away from the top electrode resonance portion 1082, and extends from the top electrode recess 1081 to the top of the partial etching protection layer 101 at the periphery of the cavity 102 after suspending above the cavity (i.e., 102B) at the outer side of the top electrode recess 1081, and the projections of the top electrode bonding portion 1080 and the bottom electrode bonding portion 1040 on the bottom surface of the cavity 102 may be directly connected to each other or separated from each other, so that the top electrode bonding portion 1080 and the bottom electrode bonding portion 1040 are not overlapped in the area of the cavity 102 and are staggered from each other. For example, as shown in fig. 1A and fig. 2A to 2C, the bottom electrode strap 1040 may extend only above a portion of the substrate at the periphery of one side of the cavity 102, the top electrode strap 1080 extends only above a portion of the substrate at the periphery of one side of the cavity 102, and the projections of the top electrode strap 1080 and the bottom electrode strap 1040 on the bottom surface of the cavity 102 are separated from each other, thereby avoiding the problems of parasitic parameters, leakage, short circuit and the like that may be caused when the top electrode strap 1080 and the bottom electrode strap 1040 are overlapped. Preferably, however, referring to fig. 2D, when the bottom electrode recess 1041 is disposed along a plurality of continuous sides of the bottom electrode resonator 1042, the bottom electrode strap 1040 is disposed along all sides of the bottom electrode recess 1041 facing away from the bottom electrode resonator 1042 and extends continuously onto the substrate at the periphery of the cavity 102, so that the bottom electrode strap 1040 can extend over a portion of the substrate at more directions at the periphery of the cavity 102, i.e. at this time, the bottom electrode strap 1040 completely covers the cavity 102 above the cavity portion where it is located, and the support force for the film layer of the active region 102A can be enhanced by laying the large-area bottom electrode strap 1040, thereby preventing the cavity 102 from collapsing. It is further preferred that when the bottom electrode strap 1040 extends above a portion of the substrate in more directions around the periphery of the cavity 102, the top electrode strap 1080 extends only above a portion of the substrate in one direction around the periphery of the cavity 102, for example, when the cavity 102 is rectangular in plan view, the top electrode strap 1080 extends only above the substrate around one side of the cavity 102, the bottom electrode strap 1040 extends to three other sides of the cavity 102, and the top electrode strap 1080 and the bottom electrode strap 1040 are directly connected or separated from each other in projection onto the bottom surface of the cavity 102, i.e., the bottom electrode strap 1040 completely covers the cavity 102 above the cavity portion where it is located, and does not overlap the top electrode strap 1080 in the width direction of the top electrode strap 1080, thereby avoiding the large area top electrode strap from being disposed vertically with the bottom electrode strap and other structures And excessive parasitic parameters are introduced due to overlapping, so that the electrical performance and the reliability of the device can be further improved.
In each embodiment of the present invention, when the cavity 102 has a polygonal top view shape, the bottom electrode overlapping portion 1040 and the top electrode overlapping portion 1080 respectively expose at least one side of the cavity, so that at least one end of each of the bottom electrode resonance portion 1042 connected to the bottom electrode recessed portion 1041 and the top electrode resonance portion 1082 connected to the top electrode recessed portion 1081 is completely suspended, which is beneficial to reducing the area of the inactive area 102B, further reducing parasitic parameters such as parasitic capacitance generated in the inactive area 102B, and improving device performance. Preferably, the bottom electrode recess 1041 is staggered with at least the top electrode overlapping portion 1080 above the cavity 102 (i.e. they do not overlap in the cavity area), the top electrode recess 1081 is staggered with at least the bottom electrode overlapping portion 1040 above the cavity 102 (i.e. they do not overlap in the cavity area), and the projections of the top electrode recess 1081 and the bottom electrode recess 1041 on the bottom surface of the cavity 102 are right in contact with each other or staggered with each other or only partially overlapped, so as to further reduce the parasitic parameters such as parasitic capacitance generated in the dead zone 102B and improve the device performance.
It should be noted that, in order to achieve the best transverse wave blocking effect and facilitate the fabrication of small-sized devices, the closer the top electrode recess 1081 and the bottom electrode recess 1041 are to the effective working area 102A, the better the line widths of the top electrode recess 1081 and the bottom electrode recess 1041 are, the better the line widths are, preferably, the line widths of the top electrode recess 1081 and the bottom electrode recess 1041 are respectively the minimum line widths allowed by the corresponding processes, and the horizontal distances between the top electrode recess 1081 and the bottom electrode recess 1041 and the effective working area 102A (i.e. the horizontal distance between the top electrode recess 1081 and the piezoelectric resonance layer 1051) are respectively the minimum distance allowed by the corresponding processes.
It is to be noted that, in the above embodiments, the top electrode resonance portion 1082 and the bottom electrode resonance portion 1042 have similar or identical shapes and have the same area, or the bottom electrode resonance portion 1042 has an area larger than that of the top electrode resonance portion 1082, but the technical solution of the present invention is not limited thereto, and in other embodiments of the present invention, the shapes of the top electrode resonance portion 1082 and the bottom electrode resonance portion 1042 may not be similar, but preferably, the shapes of the top electrode recess 1081 and the bottom electrode recess 1041 are adapted to the shape of the piezoelectric resonance layer 1051, which can extend along at least one side of the piezoelectric resonance layer 1051. In addition, it is found through research that most of the parasitic transverse waves of the bulk acoustic wave resonator are transmitted through the connection structure between the film layer on the effective working area 102A and the substrate at the periphery of the cavity, so in the embodiments of the present invention, on the premise of ensuring that the film layer of the effective working area 102A can be effectively supported, the area (or line width) of the top electrode overlapping portion 1080 can be controlled to be the smallest as possible, and the area (or line width) of the bottom electrode overlapping portion 1040 is the smallest.
An embodiment of the present invention further provides a filter, including at least one bulk acoustic wave resonator according to any of the embodiments of the present invention described above.
An embodiment of the present invention further provides a radio frequency communication system, including at least one filter according to an embodiment of the present invention.
Referring to fig. 3, an embodiment of the invention further provides a method for manufacturing a bulk acoustic wave resonator (for example, the bulk acoustic wave resonators shown in fig. 1A to 2D) of the invention, including:
s1, providing a substrate, and forming a first sacrificial layer on a part of the substrate;
s2, forming a first groove in an edge portion of the first sacrificial layer, the first groove not exposing a surface of the substrate under the first sacrificial layer;
s3, forming a bottom electrode layer on the first sacrificial layer, wherein the bottom electrode layer covers the part on the surface of the first groove to form a bottom electrode concave part;
s4, forming a piezoelectric resonance layer on the bottom electrode layer, wherein the piezoelectric resonance layer exposes the bottom electrode sunken part;
s5, forming a second sacrificial layer in the exposed area around the piezoelectric resonance layer, wherein a second groove is formed in the second sacrificial layer;
s6, forming a top electrode layer on the piezoelectric resonance layer and a part of the second sacrificial layer around the piezoelectric resonance layer, wherein the part of the top electrode layer covering the second groove forms a top electrode recess;
s7, removing the second sacrificial layer and the first sacrificial layer, wherein cavities are formed at the positions of the second sacrificial layer and the first sacrificial layer.
Referring to fig. 1A and 1B and fig. 4A to 4B, in step S1 of the present embodiment, a first sacrificial layer is formed on a portion of a substrate by a process of etching the substrate to form a groove and filling a material into the groove, and the specific implementation process includes:
first, referring to fig. 1A and fig. 4A, a substrate, specifically, a base 100 is provided, and an etching protection layer 101 is covered on the base 100. The etching protection layer 101 may be formed on the substrate 100 by any suitable process, such as a thermal treatment method, such as thermal oxidation, thermal nitridation or thermal oxynitridation, or a deposition method, such as chemical vapor deposition, physical vapor deposition or atomic layer deposition. Further, the thickness of the etching protection layer 101 may be set reasonably according to the actual device process requirements, and is not limited specifically herein.
Next, with continued reference to fig. 1A, 1B and 4A, the substrate is etched by photolithography and etching processes to form at least one third recess 102'. The etching process may be a wet etching or a dry etching process, wherein preferably a dry etching process is used, including but not limited to Reactive Ion Etching (RIE), ion beam etching, plasma etching or laser cutting. The depth and shape of the third groove 102 ' are determined by the depth and shape of the cavity required by the bulk acoustic wave resonator to be manufactured, the cross-sectional shape of the third groove 102 ' is rectangular, and in other embodiments of the present invention, the cross-section of the third groove 102 ' may be any other suitable shape, such as a circle, an ellipse, or other polygons (e.g., pentagon, hexagon, etc.) except a rectangle.
Then, referring to fig. 1A, 1B and 4B, a first sacrificial layer 103 is formed to fill the third recess 102'. The first sacrificial layer 103 includes a first sub-sacrificial layer 1031 and a second sub-sacrificial layer 1032 which are made of different materials and stacked from bottom to top, and the arrangement of the first sub-sacrificial layer 1031 and the second sub-sacrificial layer 1032 can enable a stop point of etching to be accurately controlled when a first groove is formed by etching in the subsequent process, so as to accurately control a recess depth of a bottom electrode recess 1041 formed in the subsequent process, and thus, the thickness of the second sub-sacrificial layer 1032 determines the recess depth of the bottom electrode recess 1041 formed in the subsequent process. Wherein two methods can be employed to form the first sacrificial layer 103.
With continued reference to fig. 1A, 1B and 4B, a method for filling the third recess 102' with the first sacrificial layer 103 includes: first, filling a first sub-sacrificial layer 1031 in the third recess 102 ' by a vapor deposition or epitaxial growth process, where the first sub-sacrificial layer 1031 is selected to be a material that can be processed by some processes and then converted into a material different from the substrate 100 and the etching protection layer 101, and in this embodiment, the first sub-sacrificial layer 1031 is selected to be a semiconductor material different from the substrate 100 and is formed on the substrate by a chemical vapor deposition process, and at this time, the first sub-sacrificial layer 1031 not only fills the third recess 102 ', but also covers the surface of the etching protection layer 101 around the third recess 102 '; then, planarizing the top of the first sub sacrificial layer 1031 to the top surface of the etching protection layer 101 by a Chemical Mechanical Planarization (CMP) process, so that the first sub sacrificial layer 1031 is only located in the third recess 102'; then, a suitable surface modification treatment process is selected according to the material of the first sub-sacrificial layer 1031, for example, at least one of oxidation treatment, nitridation treatment and ion implantation is included, performing surface modification treatment on the top of the first sub sacrificial layer 1031 with a certain thickness, so that the part of the thickness of the first sub sacrificial layer 1031 is converted into a second sub sacrificial layer 1032 made of another material, the second sub-sacrificial layer 1032 and the remaining first sub-sacrificial layer 1031 under it without being surface-modified constitute a first sacrificial layer filling the third recess 102', for example, when the substrate 100 is a Si substrate, the first sub-sacrificial layer 1031 is Ge, and the etching protection layer 101 is silicon oxide, in an oxygen atmosphere, a certain thickness of the top of the first sub sacrificial layer 1031 is subjected to oxidation treatment to convert it into germanium oxide, as the second sub-sacrificial layer 1032, the thickness of the second sub-sacrificial layer 1032 depends on the recess depth of the bottom electrode recess 1041 to be formed later; afterwards, since the surface treatment process may cause the top surface of the filled first sacrificial layer 103 to be no longer flush with the top surface of the etching protection layer 101 around the filled first sacrificial layer, which is not favorable for the subsequent formation of a flat acoustic membrane, it is necessary to further planarize the top of the second sub-sacrificial layer 1032 to the top surface of the etching protection layer 101 through a Chemical Mechanical Planarization (CMP) process, so that the top surface of the first sacrificial layer 103 is flush with the top surface of the etching protection layer 101 around the filled first sacrificial layer again, so as to provide a relatively flat operation surface for the subsequent process.
With continued reference to fig. 1A, 1B and 4B, another method for filling the third recess 102' with the first sacrificial layer 103 includes: first, a material used as the first sub-sacrificial layer 1031 may be filled in the third recess 102 'by an appropriate process such as an epitaxial growth process, a thermal oxidation process, a vapor deposition process or a coating process, the material of the first sub-sacrificial layer 1031 may be any material known to those skilled in the art that does not conform to the etching of the protection layer 101 and the substrate 100, such as amorphous carbon, photoresist, a dielectric material (e.g., silicon nitride, silicon oxycarbide, a porous material, etc.) or a semiconductor material (e.g., polysilicon, amorphous silicon, germanium), and the first sub-sacrificial layer 1031 formed at this time at least fills the third recess 102'; then, back-etching the material of the first sub-sacrificial layer 1031 by using a dry etching process or a wet etching process to remove the material of the first sub-sacrificial layer 1031 outside the third recess 102 ', and making the top surface of the material of the first sub-sacrificial layer 1031 in the third recess 102' lower than the top surface of the substrate 100 to form the first sub-sacrificial layer 1031, where the back-etching depth depends on the depth of a first recess to be formed later (i.e. the recess depth of a bottom electrode recess in a bottom electrode); then, a second sub-sacrificial layer 1032 is filled in the third recess 102 ' by an appropriate process such as an epitaxial growth process, a thermal oxidation process, a vapor deposition process, or a coating process, the second sub-sacrificial layer 1032 fills the third recess 102 ' and has a material different from that of the first sub-sacrificial layer 1031, the second sub-sacrificial layer 1032 and the first sub-sacrificial layer 1031 thereunder form the first sacrificial layer 103 filling the third recess 102 ', and the material of the second sub-sacrificial layer 1032 is, for example, a dielectric material such as silicon nitride, silicon oxynitride, phosphosilicate glass, or the like.
Referring to fig. 1A, 1B and 4C, in step S2, the first sacrificial layer 103 may be etched to correspond to the active working area of the bulk acoustic wave resonator to be fabricated by a process of photolithography and etching (as shown in fig. 4H)102A), the etching may stop at the top surface of the first sub-sacrificial layer 1031, or there may be a certain over-etching to stop in the first sub-sacrificial layer 1031, so as to form a first groove 1033, and the line width, size, shape, and position of the first groove 1033 determine the line width, size, shape, and position of a bottom electrode recess in a subsequently formed bottom electrode. In this embodiment, the longitudinal cross section of the first groove 1033 along XX' in fig. 2A is trapezoidal, and an included angle between the sidewall of the first groove 1033 and the top surface of the second sub-sacrificial layer 1032 is
Less than 45 degrees, thereby facilitating the deposition of the subsequent bottom electrode material layer, and further improving the thickness uniformity of the subsequently formed bottom electrode layer in the third groove 102'. In other embodiments of the present invention, the cross-sectional shape of the first groove 1033 may also be a spherical cap with a wide top and a narrow bottom, i.e., a U-shaped longitudinal cross-section along line XX' of fig. 1A. The horizontal distance between the first recess 1033 and the active region 102A is preferably a minimum distance allowed by a process for etching and aligning the first recess 1033, and a line width of the first recess 1033 is a minimum line width allowed by a corresponding process.
Referring to fig. 1A, 1B and 4D, in step S3, first, a bottom electrode material layer (not shown) may be covered on the surfaces of the etching protection layer 101, the second sub-sacrificial layer 1032 and the first groove 1033 by a suitable method selected according to a material of a bottom electrode to be formed, for example, the bottom electrode material layer may be formed by a physical vapor deposition method such as magnetron sputtering or evaporation, or a chemical vapor deposition method; then, a photoresist layer (not shown) with a bottom electrode pattern defined thereon is formed on the bottom electrode material layer by using a photolithography process, the bottom electrode material layer is etched using the photoresist layer as a mask to form a bottom electrode layer (i.e., the remaining bottom electrode material layer) 104, and then the photoresist layer is removed. The bottom electrode material layer may use any suitable conductive material or semiconductor material known in the art, wherein the conductive material may be a metal material having a conductive property, such as one or more of aluminum (Al), copper (Cu), platinum (Pt), gold (Au), molybdenum (Mo), tungsten (W), iridium (Ir), osmium (Os), rhenium (Re), palladium (Pd), rhodium (Rh), and ruthenium (Ru), or a semiconductor material, such as Si, Ge, SiGe, SiC, SiGeC, or the like. In this embodiment, the bottom electrode layer (remaining bottom electrode material layer) 104 includes a bottom electrode resonance portion 1042 covering the active working region 102A to be formed later, a bottom electrode recess 1041 covering the first recess 1033, a bottom electrode strap 1040 extending from one side of the bottom electrode recess 1041 to the portion of the etching protection layer 101 outside the third recess 102' through the surface of the second sub-sacrificial layer 1032, and a bottom electrode peripheral portion 1043 separated from the bottom electrode resonance portion 1042 and the bottom electrode recess 1041, the bottom electrode peripheral portion 1043 may be connected to a side of the bottom electrode strap 1040 facing away from the bottom electrode resonating portion 1042, to serve as a metal contact for the bulk acoustic wave resonator to be formed in this region, may also be separate from the bottom electrode strap 1040 as part of the bottom electrode strap of an adjacent bulk acoustic wave resonator, and in other embodiments of the present invention, the bottom electrode peripheral portion 1043 may be omitted. The bottom electrode resonator 1042 may be pentagonal in top view, and in other embodiments of the present invention, may also be quadrilateral or hexagonal, and the bottom electrode recess 1041 is disposed between the bottom electrode strap 1040 and the bottom electrode resonator 1042, the bottom electrode recess 1041 is disposed along at least one side of the bottom electrode resonator 1042 and connected to a corresponding side of the bottom electrode resonator 1042, the bottom electrode strap 1040 is electrically connected to at least one side or at least one corner of the bottom electrode recess 1041 facing away from the bottom electrode resonator 1042, and extends from the corresponding side of the bottom electrode recess 1041 to a top surface of a partially etched protection layer 101 at the periphery of the third recess 102' through a top surface of a second sub-sacrificial layer 1032 covering the outside of the bottom electrode recess 1041, that is, the bottom electrode recess 1041 is disposed along the side of the bottom electrode resonator 1042 and at least disposed in a region where the bottom electrode strap 1040 is aligned with the bottom electrode resonator 1042 For example, the bottom electrode recess 1041 may surround the bottom electrode resonance portion 1042 for a circle to form a closed loop structure (see fig. 2C), may be disposed along only one side of the bottom electrode resonance portion 1042, or may be disposed along two or more continuous sides of the bottom electrode resonance portion 1042 (see fig. 2A-2B, and 2D). The shape, line width, horizontal distance from the active region 102A, and the like of the bottom electrode recess 1041 are determined by the forming process of the first groove 1033. Preferably, the bottom electrode overlapping portion 1040 completely covers the cavity 102 above the cavity portion where it is located, and has no overlap with the top electrode overlapping portion 1080 in the width direction of the top electrode overlapping portion 1080, so as to improve the supporting force for the subsequent film layer and avoid the overlap with the top electrode overlapping portion 1080 as much as possible to introduce unnecessary parasitic parameters. The bottom electrode resonance section 1042 may function as an input electrode or an output electrode that receives or provides an electrical signal such as a Radio Frequency (RF) signal. In this embodiment, the bottom electrode recessed portion 1041 is not filled in the first groove 1033, the upper surface thereof forms a hollow structure, and the bottom electrode recessed portion 1041, the bottom electrode resonance portion 1042 and the bottom electrode bonding portion 1040 have the same thickness, but the invention is not limited thereto, and in other embodiments of the invention, the bottom electrode recessed portion 1041 may also be a solid structure filled in the first groove 1033.
Referring to fig. 1A, 1B and 4E, in step S4, the piezoelectric material layer 105 may be deposited by any suitable method known to those skilled in the art, such as chemical vapor deposition, physical vapor deposition or atomic layer deposition; then, a photoresist layer (not shown) with a piezoelectric thin film pattern defined thereon is formed on the piezoelectric material layer 105 by a photolithography process, the piezoelectric material layer 105 is etched using the photoresist layer as a mask to form the piezoelectric resonance layer 1051, and then the photoresist layer is removed. As the material of the piezoelectric material layer 105, aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), lithium niobate (LiNbO) can be used3) Quartz (Quartz), potassium niobate (KNbO)3) Or lithium tantalate (LiTaO)3) And the like, and combinations thereof. When the piezoelectric material layer 105 includes aluminum nitride (AlN), the piezoelectric material layer 105 may further include a rare earth metal, for example, at least one of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La). In addition, when the piezoelectric material layer 105 is wrappedWhen aluminum nitride (AlN) is included, the piezoelectric material layer 105 may further include a transition metal, such as at least one of zirconium (Zr), titanium (Ti), manganese (Mn), and hafnium (Hf). The piezoelectric material layer 105 remaining after patterning includes a piezoelectric resonance layer 1051 and a piezoelectric peripheral portion 1050 that are separated from each other, the piezoelectric resonance layer 1051 is located on the bottom electrode resonance portion 1042, exposes the bottom electrode recess 1041, and may completely cover or partially cover the bottom electrode resonance portion 1042. The shape of the piezoelectric resonance layer 1051 may be the same as or different from that of the bottom electrode resonance section 1042, and the planar shape thereof may be pentagonal or other polygonal shapes such as a quadrangle, a hexagon, a heptagon, or an octagon. The piezoelectric peripheral portion 1050 can form a gap with the piezoelectric resonance layer 1051 to expose the bottom electrode recess 1041 and the second sub sacrificial layer 1032 around the bottom electrode resonance portion 1042, and further limit a formation region of a subsequent second sacrificial layer by the formed gap, while providing a relatively flat process surface for formation of a subsequent second recess, and the piezoelectric peripheral portion 1050 can also achieve isolation between a subsequently formed top electrode peripheral portion and a previously formed bottom electrode peripheral portion 1043, while providing a relatively flat process surface for formation of a subsequent second sacrificial layer and a top electrode.
Referring to fig. 1A, 1B and 4F, in step S5, first, by a suitable process such as a coating process or a vapor deposition process, second sacrificial layer 106 is covered in piezoelectric peripheral portion 1050 and piezoelectric resonance layer 1051 and the gap between piezoelectric peripheral portion 1050 and piezoelectric resonance layer 1051, and second sacrificial layer 106 can fill the gap between piezoelectric periphery 1050 and piezoelectric resonator layer 1051, the material of the second sacrificial layer 106 may be at least one selected from amorphous carbon, photoresist, dielectric material (e.g. silicon nitride, silicon oxycarbide, porous material, etc.), semiconductor material (e.g. polysilicon, amorphous silicon, germanium), etc., the material of the second sacrificial layer 106 is preferably different from the first sacrificial layer 103, in order to be able to form the second recess 107 subsequently in the etching process, the top surface of the first sacrificial layer 103 is used as an etching stop point, and further the depth of the second recess 107 formed subsequently is controlled; then, the second sacrificial layer 106 is top-planarized by a CMP process so that the second sacrificial layer 106 is filled only in the gap between the piezoelectric periphery 1050 and the piezoelectric resonance layer 1051, and the piezoelectric periphery 1050, the piezoelectric resonance layer 1051, and the second sacrificial layer 106 constitute a flat upper surface. In other embodiments of the present invention, the second sacrificial layer 106 on the upper surfaces of the piezoelectric peripheral portion 1050 and the piezoelectric resonance layer 1051 may also be removed by an etch-back process so as to fill only the gap between the piezoelectric peripheral portion 1050 and the piezoelectric resonance layer 1051. Then, the second sacrificial layer 106 is patterned by photolithography or a process combining photolithography and etching to form a second groove 107, and the shape, size, position, and the like of the second groove 107 determine the shape, size, position, and the like of a subsequently formed top electrode recess. Preferably, the side wall of the second groove 107 is an inclined side wall inclined relative to the plane where the piezoelectric resonance layer 1051 is located, and included angles θ 1 and θ 2 between the side wall of the second groove 107 and the top surface of the piezoelectric resonance layer 1051 are both smaller than or equal to 45 degrees, so that the material coverage of the subsequent top electrode concave portion 1081 is facilitated, the occurrence of fracture is avoided, and the thickness uniformity is improved. Further preferably, the line width of the second groove 107 is the minimum line width allowed by the corresponding process, and the horizontal distance between the second groove 107 and the piezoelectric resonance layer 1051 is the minimum distance allowed by the corresponding process, thereby facilitating the reduction of the device size while achieving a better transverse wave blocking effect. In other embodiments of the present invention, when the second groove 107 and the first groove 103 do not have an overlapping portion in the vertical direction, after etching the second sacrificial layer 106, there may be a certain over-etching, so that the bottom surface of the formed second groove 107 stops in a certain thickness of the first sacrificial layer 103, for example, the second groove 107 reaches the top surface of the first sub-sacrificial layer 1031, thereby making it possible to make the subsequently formed top electrode recess 1081 compensate for the portion of the side of the bottom electrode recess 1041 not surrounding the piezoelectric resonance layer 1051, so that the combination of the top electrode recess 1081 and the bottom electrode recess 1041 may surround the piezoelectric resonance layer 1051. In other embodiments of the present invention, the second sacrificial layer 106 and the second groove 107 may be formed by referring to the method for forming the first sacrificial layer 103 and the first groove 1033 in steps S1 to S2, which is not described herein again.
Referring to fig. 1A, fig. 1B and fig. 4G, in step S6, a top electrode material layer (not shown) may be first formed on the surfaces of the piezoelectric periphery 1050, the piezoelectric resonator layer 1051, the second sacrificial layer 106 and the second recess 107 by selecting a suitable method according to a material of a top electrode to be formed, for example, by physical vapor deposition such as magnetron sputtering or evaporation, or chemical vapor deposition, and the top electrode material layer may have a uniform thickness at each position; then, a photoresist layer (not shown) with a top electrode pattern defined thereon is formed on the top electrode material layer by using a photolithography process, the top electrode material layer is etched using the photoresist layer as a mask to form a top electrode layer (i.e., the patterned top electrode material layer or the remaining top electrode material layer) 108, and then the photoresist layer is removed. The top electrode material layer may use any suitable conductive material or semiconductor material known in the art, wherein the conductive material may be a metal material with conductive property, such as one or more of Al, Cu, Pt, Au, Mo, W, Ir, Os, Re, Pd, Rh, and Ru, and the semiconductor material may be Si, Ge, SiGe, SiC, SiGeC, etc. In this embodiment, the top electrode layer 108 includes a top electrode resonance portion 1082 covering the piezoelectric resonance layer 1051, a top electrode recess 1081 covering the second groove 107, a top electrode lap 1080 extending from the top electrode recess 1081 to the piezoelectric peripheral portion 1050 outside the top electrode recess 1081 through a part of the top surface of the second sacrificial layer 106, and a top electrode peripheral portion 1083 separated from both the top electrode resonance portion 1082 and the top electrode recess 1081, the top electrode peripheral portion 1083 may be connected to a side of the top electrode lap 1080 facing away from the top electrode resonance portion 1082 to serve as one metal contact of the bulk acoustic wave resonator to be formed in the area, and may be separated from the top electrode lap 1080 to serve as a part of the top electrode lap of an adjacent bulk acoustic wave resonator, and in other embodiments of the present invention, the top electrode peripheral portion 1083 may be omitted. The top electrode resonance portion 1082 may have the same or different top view shape as that of the piezoelectric resonance layer 1051, for example, a pentagonal top view shape, and preferably has an area larger than that of the piezoelectric resonance layer 1051, so that the piezoelectric resonance layer 1051 is completely sandwiched by the top electrode resonance portion 1082 and the bottom electrode resonance portion 1042, thereby facilitating reduction of the device size and parasitic parameters. The top electrode layer 108 may serve as an input electrode or an output electrode that receives or provides electrical signals, such as Radio Frequency (RF) signals. For example, when the bottom electrode layer 104 is used as an input electrode, the top electrode layer 108 may be used as an output electrode, and when the bottom electrode layer 104 is used as an output electrode, the top electrode layer 108 may be used as an input electrode, and the piezoelectric resonance layer 1051 converts an electric signal input through the top electrode resonance portion 1082 or the bottom electrode resonance portion 1042 into a bulk acoustic wave. For example, the piezoelectric resonance layer 1051 converts an electric signal into a bulk acoustic wave by physical vibration. The top electrode recessed portion 1081 is disposed along at least one side of the top electrode resonance portion 1082 and is connected to a corresponding side of the top electrode resonance portion 1082, i.e., the top electrode recessed portion 1081 is disposed along the side of the top electrode resonance portion 1082 and is disposed at least in an area where the top electrode lap portion 1080 and the top electrode resonance portion 1082 are aligned, e.g., the top electrode recessed portion 1081 surrounds the top electrode resonance portion 1082 for a circumference to form a closed loop structure (as shown in fig. 2C and 2D), and further, e.g., the top electrode recessed portion 1081 extends over a plurality of continuous sides of the top electrode resonance portion 1082 to form an open loop structure (as shown in fig. 2A and 2B). The top electrode strap 1080 is electrically connected to a side of the top electrode recess 1081 facing away from the top electrode resonance portion 1082, and extends from the top electrode recess 1081 to a top surface of a portion of the etching protection layer 101 outside the third groove 102 'through a top surface of a portion of the second sacrificial layer 106, the top electrode strap 1080 and the bottom electrode strap 1040 are staggered with respect to each other (i.e., they do not overlap in a region of the cavity 102), and the top electrode strap 1080 and the bottom electrode strap 1040 respectively expose at least one side of the third groove 102'. In an embodiment of the invention, referring to fig. 2A and 2B, in a direction perpendicular to the bottom surface of the third groove 102', the top electrode recessed portion 1081 and the bottom electrode overlapping portion 1040 do not overlap with each other at an edge facing the bottom electrode recessed portion 1041, and the bottom electrode recessed portion 1041 and the top electrode overlapping portion 1080 do not overlap with each other at an edge facing the top electrode recessed portion 1081. The projections of the top electrode strap 1080 and the bottom electrode strap 1040 on the bottom surface of the third recess 102 'are directly connected or separated from each other, and the top electrode strap 1080 may extend only over a portion of the substrate at the periphery of one side of the third recess 102'.
Referring to fig. 1A, 1B and 4H, in step S7, a hole may be punched at an edge of the piezoelectric peripheral portion 1050 facing the third groove 102' or at a periphery of the device region of the bulk acoustic wave resonator by a photolithography combined with an etching process or a laser cutting process to form a release hole (not shown) capable of exposing at least one of a portion of the first sacrificial layer 103, a portion of the second groove 107 or the second sacrificial layer 106 exposed by the second groove 107; then, gas and/or liquid medicine is introduced into the release hole to remove the second groove 107, the second sacrificial layer 106 and the first sacrificial layer 103, and the third groove is emptied again to form a cavity 102, where the cavity 102 includes a space of the third groove 102' limited by the bottom electrode recess 1041, a space increased by the top electrode recess 1081, and a space under the top electrode recess 1081 and originally occupied by the second sacrificial layer 106. Here, the bottom electrode resonance portion 1042, the piezoelectric resonance layer 1051, and the top electrode resonance portion 1082 suspended above the cavity 102 and stacked in this order constitute an exclusive stereo thin film, and a portion where the bottom electrode resonance portion 1042, the piezoelectric resonance layer 1051, the top electrode resonance portion 1082, and the cavity 102 are overlapped with each other in a vertical direction is an effective area defined as an effective working area 102A, in which, when electric power such as a radio frequency signal is applied to the bottom electrode resonance portion 1042 and the top electrode resonance portion 1082, vibration and resonance are generated in a thickness direction (i.e., a longitudinal direction) of the piezoelectric resonance layer 1051 due to a piezoelectric phenomenon generated in the piezoelectric resonance layer 1051, and the other area of the cavity 102 is an ineffective area 102B in which, even when electric power is applied to the top electrode layer 108 and the bottom electrode layer 104, an area that is not resonated due to the piezoelectric phenomenon is not generated in the ineffective area 102B. The independent acoustic thin film composed of the bottom electrode resonance portion 1042, the piezoelectric resonance layer 1051, and the top electrode resonance portion 1082 suspended above the effective working area 102A and stacked in this order can output a radio frequency signal of a resonance frequency corresponding to the vibration of the piezoelectric phenomenon of the piezoelectric resonance layer 1051. Specifically, when electric power is applied to the top electrode resonance portion 1082 and the bottom electrode resonance portion 1042, a bulk acoustic wave is generated by a piezoelectric phenomenon generated in the piezoelectric resonance layer 1051. In this case, the generated bulk acoustic wave has a parasitic transverse wave in addition to the desired longitudinal wave, and the transverse wave is blocked at the top electrode recess 1081 and the bottom electrode recess 1041, and the transverse wave is confined in the active region 102A and prevented from propagating into the film layer on the periphery of the cavity, thereby improving acoustic loss caused by propagation of the transverse wave into the film layer on the periphery of the cavity, so that the quality factor of the resonator is improved, and finally the device performance can be improved.
It should be noted that the step S7 may be performed after all the film layers above the cavity 102 to be formed are manufactured, so that the first sacrificial layer 103 and the second sacrificial layer 106 may be continuously utilized to protect the space where the cavity 102 is located and the film layer structure formed thereon by stacking the bottom electrode layer 104 to the top electrode layer 108, so as to avoid the risk of cavity collapse when the subsequent processes are continued after the cavity 102 is formed. In addition, the release hole formed in step S7 may be left at all times, so that the release hole can be sealed by a subsequent packaging process such as two-substrate bonding, thereby closing the cavity 102.
It should be noted that, in step S1 of the method for manufacturing a bulk acoustic wave resonator according to each of the above embodiments, the first sacrificial layer 103 is formed on a portion of the substrate by a process of etching the substrate to form the third recess 102 ' and filling the third recess 102 ', so that the cavity 102 formed in step S7 is a recess structure with the entire bottom recessed in the substrate, but the technical solution of the present invention is not limited thereto, and in step S1 of other embodiments of the present invention, the first sacrificial layer 103 protruding on the substrate may be formed by a film deposition in combination with a photolithography and etching process, so that the cavity 102 formed in step S7 is a cavity structure protruding on the substrate surface as a whole, specifically, referring to fig. 2E and 5, in step S1, the third recess 102 ' for making the cavity 102 is not formed in the provided substrate, but the first sub sacrificial layer 1031 and the second sub sacrificial layer 1032 are sequentially covered on the etching protection layer 101 on the surface of the substrate 100, the formation process of the first sub-sacrificial layer 1031 and the second sub-sacrificial layer 1032 can refer to the above embodiment, that is, the first sub-sacrificial layer 1031 and the second sub-sacrificial layer 103 stacked together can be formed by a process of continuously depositing two film layers of different materials or by a process of converting the materials of the top of a thicker film layer deposited in advance by a certain thickness; then, by a process of photolithography and etching, the second sub-sacrificial layer 1032 and the first sub-sacrificial layer 1031 are patterned, and only the second sub-sacrificial layer 1032 and the first sub-sacrificial layer 1031 covering the region corresponding to the cavity 102 remain, and further the first sacrificial layer 103 is on a portion of the substrate, where the first sacrificial layer 103 may be a structure with a narrow top and a wide bottom, and the thickness of the first sacrificial layer 103 determines the depth of the cavity 102 to be formed subsequently. In this embodiment, the subsequent steps are completely the same as those of the corresponding parts in the method for manufacturing the bulk acoustic wave resonator of the embodiment shown in fig. 4A to 4H, and are not repeated herein, except that the corresponding sidewalls of the formed bottom electrode peripheral portion 1043, the bottom electrode bridging portion 1040, the piezoelectric peripheral portion 1050, the top electrode peripheral portion 1083, and the top electrode bridging portion 1080 need to be deformed to adapt to the protruding first sacrificial layer 103, and the longitudinal cross section of each of the sidewalls is changed into a "Z" shaped structure.
The bulk acoustic wave resonator of the present invention preferably employs the method for manufacturing a bulk acoustic wave resonator of the present invention, so that the bottom electrode lap joint portion, the bottom electrode recess portion and the bottom electrode resonance portion are manufactured together, and the top electrode lap joint portion, the top electrode recess portion and the top electrode resonance portion are manufactured together, thereby simplifying the process and reducing the manufacturing cost.
It will be apparent to those skilled in the art that various changes and modifications may be made in the invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (26)
1. A bulk acoustic wave resonator, comprising:
a substrate;
the bottom electrode layer is arranged on the substrate, a cavity is formed between the bottom electrode layer and the substrate, the bottom electrode layer is provided with a bottom electrode sunken part, and the bottom electrode sunken part is positioned in the area of the cavity and is sunken towards the direction close to the bottom surface of the cavity;
a piezoelectric resonance layer formed on the bottom electrode layer above the cavity;
the top electrode layer is formed on the piezoelectric resonance layer, the top electrode layer has a top electrode depressed part, the top electrode depressed part is located in the region of cavity and towards being close to the direction of the bottom surface of cavity is sunken, the top electrode depressed part with the bottom electrode depressed part all is located in the outlying cavity region of piezoelectric resonance layer, the bottom electrode depressed part with the top electrode depressed part all centers on the peripheral direction extension of piezoelectric resonance layer, and the two is at least partially relative.
2. The bulk acoustic wave resonator according to claim 1, wherein the bottom electrode layer further comprises a bottom electrode lap, one end of the bottom electrode lap being connected to the bottom electrode recess, and the other end being lap-jointed to the substrate on the periphery of the cavity; the top electrode layer further comprises a top electrode overlapping part, one end of the top electrode overlapping part is connected with the top electrode sunken part, and the other end of the top electrode overlapping part extends to the position above the substrate on the periphery of the cavity; the bottom electrode overlapping part and the top electrode overlapping part are staggered with each other.
3. The bulk acoustic wave resonator according to claim 2, wherein the bottom electrode layer further includes a bottom electrode resonance portion overlapping the piezoelectric resonance layer, the top electrode layer further includes a top electrode resonance portion overlapping the piezoelectric resonance layer, and the bottom electrode resonance portion and the top electrode resonance portion are each polygonal.
4. The bulk acoustic wave resonator according to claim 3, wherein the bottom electrode recess is provided along a side of the bottom electrode resonance section and at least in a region where the bottom electrode lap and the bottom electrode resonance section are aligned, and the top electrode recess is provided along a side of the top electrode resonance section and at least in a region where the top electrode lap and the top electrode resonance section are aligned.
5. The bulk acoustic wave resonator according to claim 4, wherein the bottom electrode recess is offset from at least the top electrode lap above the cavity, or wherein the bottom electrode recess surrounds the bottom electrode resonance portion by one revolution; the top electrode sunken part is at least staggered with the bottom electrode overlapping part above the cavity, or the top electrode sunken part surrounds the top electrode resonance part for a circle.
6. The bulk acoustic resonator according to claim 5, wherein the projections of the top electrode recess and the bottom electrode recess on the bottom surface of the cavity are right next to each other or are staggered or have an overlap.
7. The bulk acoustic wave resonator according to claim 3, wherein the bottom electrode recess, the bottom electrode lap and the bottom electrode resonance portion are formed using the same film layer, and the top electrode recess, the top electrode lap and the top electrode resonance portion are formed using the same film layer.
8. The bulk acoustic wave resonator according to claim 4, wherein the bottom electrode lap completely covers the cavity above a portion of the cavity where it is located, and does not overlap with the top electrode lap in a width direction of the top electrode lap.
9. The bulk acoustic wave resonator according to any one of claims 1 to 8, wherein a horizontal distance between the bottom electrode recess and the piezoelectric resonance layer is a minimum distance allowed by a process of manufacturing the bottom electrode recess; the horizontal distance between the top electrode recess and the piezoelectric resonance layer is a minimum distance allowed by a process of manufacturing the top electrode recess.
10. The bulk acoustic wave resonator according to any one of claims 1 to 8, wherein the side wall of the top electrode recess is inclined with respect to the top surface of the piezoelectric resonance layer, and the side wall of the bottom electrode recess is inclined with respect to the bottom surface of the piezoelectric resonance layer.
11. The bulk acoustic wave resonator according to claim 10, wherein an angle between the side wall of the top electrode recess and the top surface of the piezoelectric resonance layer is 45 degrees or less, and an angle between the side wall of the bottom electrode recess and the bottom surface of the piezoelectric resonance layer is 45 degrees or less.
12. The bulk acoustic resonator according to any one of claims 1 to 8 or 11, wherein the line width of the bottom electrode recess is a minimum line width allowed by a process of manufacturing the bottom electrode recess; the line width of the top electrode recess is the minimum line width allowed by the process of manufacturing the top electrode recess.
13. The bulk acoustic wave resonator according to any one of claims 1 to 8 or 11, wherein the cavity is a groove structure whose entire bottom is recessed in the substrate or a cavity structure which is provided on a surface of the substrate as a whole.
14. A filter comprising at least one bulk acoustic wave resonator according to any one of claims 1 to 13.
15. A radio frequency communication system comprising at least one filter according to claim 14.
16. A method of manufacturing a bulk acoustic wave resonator, comprising:
providing a substrate, and forming a first sacrificial layer on a part of the substrate;
forming a first groove in an edge portion of the first sacrificial layer, the first groove not exposing a surface of the substrate under the first sacrificial layer;
forming a bottom electrode layer on the first sacrificial layer, wherein a bottom electrode concave part is formed on the part, covered on the surface of the first groove, of the bottom electrode layer;
forming a piezoelectric resonance layer on the bottom electrode layer, wherein the piezoelectric resonance layer exposes the bottom electrode sunken part;
forming a second sacrificial layer in the exposed area around the piezoelectric resonance layer, wherein a second groove is formed in the second sacrificial layer;
forming a top electrode layer on the piezoelectric resonance layer and a part of the second sacrificial layer around the piezoelectric resonance layer, wherein the part of the top electrode layer covering the second groove forms a top electrode concave part;
and removing the second sacrificial layer and the first sacrificial layer, forming a cavity at the position of the second sacrificial layer and the first sacrificial layer, wherein the top electrode concave part and the bottom electrode concave part are both positioned in the cavity area at the periphery of the piezoelectric resonance layer, and the bottom electrode concave part and the top electrode concave part extend around the peripheral direction of the piezoelectric resonance layer and are at least partially opposite to each other.
17. The method of fabricating a bulk acoustic wave resonator according to claim 16, wherein the step of forming the first sacrificial layer on the portion of the substrate comprises: etching the substrate to form a third groove in the substrate; forming a first sacrificial layer to fill in the third groove; alternatively, the first and second electrodes may be,
the step of forming a first sacrificial layer on a portion of a substrate includes: covering a first sacrificial layer on the substrate; and patterning the first sacrificial layer to form a first sacrificial layer protruding from a part of the substrate.
18. The method of manufacturing a bulk acoustic wave resonator according to claim 17, wherein the first sacrifice layer includes a first sub-sacrifice layer and a second sub-sacrifice layer which are stacked in this order, wherein,
the step of forming the first sub-sacrificial layer and the second sub-sacrificial layer stacked in this order includes: firstly, forming a first sub sacrificial layer; then, performing material conversion on the top of the first sub sacrificial layer with a certain thickness to convert the top of the first sub sacrificial layer into a second sub sacrificial layer with a material different from that of the first sub sacrificial layer; alternatively, the first and second electrodes may be,
the step of forming the first sub-sacrificial layer and the second sub-sacrificial layer stacked in this order includes: firstly, forming a first sub sacrificial layer; and then, forming a second sub-sacrificial layer on the first sub-sacrificial layer, wherein the first sub-sacrificial layer and the second sub-sacrificial layer are made of different materials.
19. The method of manufacturing a bulk acoustic wave resonator according to claim 18, wherein the second sub-sacrificial layer is formed by converting a material of a certain thickness on top of the first sub-sacrificial layer by a surface modification process including at least one of an oxidation process, a nitridation process, and an ion implantation process.
20. The method of manufacturing a bulk acoustic wave resonator according to claim 18, wherein a bottom surface of the first groove stops on a top surface of the first sub sacrificial layer or in the first sub sacrificial layer.
21. The method of manufacturing a bulk acoustic wave resonator according to claim 16, wherein the step of removing the second sacrificial layer having the second groove and the first sacrificial layer includes:
after forming the top electrode layer, forming at least one release hole, wherein the release hole at least exposes a part of the first sacrificial layer, a part of the second groove or a part of the second sacrificial layer except the second groove;
and introducing gas and/or liquid medicine into the release hole to remove the second sacrificial layer with the second groove and the first sacrificial layer.
22. The method of manufacturing a bulk acoustic wave resonator according to any one of claims 16 to 21, wherein the step of forming the bottom electrode layer includes: depositing a bottom electrode material layer to cover the first sacrificial layer with the first groove; and patterning the bottom electrode material layer to form a bottom electrode overlapping part, a bottom electrode sunken part and a bottom electrode resonance part which are sequentially connected, wherein the bottom electrode resonance part is overlapped with the piezoelectric resonance layer, and one end, back to the bottom electrode sunken part, of the bottom electrode overlapping part is overlapped on the substrate on the periphery of the cavity.
23. The method of manufacturing a bulk acoustic wave resonator according to claim 22, wherein the step of forming the top electrode layer includes: depositing a top electrode material layer to cover the second sacrificial layer with the second groove and the piezoelectric resonance layer; patterning the top electrode material layer to form a top electrode overlapping part, a top electrode depressed part and a top electrode resonance part which are connected in sequence, wherein the top electrode resonance part is overlapped with the piezoelectric resonance layer, one end of the top electrode overlapping part, which faces away from the top electrode depressed part, extends to the upper part of the substrate on the periphery of the cavity, and the top electrode overlapping part and the bottom electrode overlapping part are staggered with each other.
24. The method of manufacturing a bulk acoustic wave resonator according to claim 23, wherein the bottom electrode resonance section and the top electrode resonance section are each polygonal, the bottom electrode recess section is provided along a side of the bottom electrode resonance section and at least in a region where the bottom electrode lap section and the bottom electrode resonance section are aligned, and the top electrode recess section is provided along a side of the top electrode resonance section and at least in a region where the top electrode lap section and the top electrode resonance section are aligned.
25. The method of manufacturing a bulk acoustic wave resonator according to any one of claims 16 to 21 and 23 to 24, wherein a horizontal distance between the bottom electrode recess and the piezoelectric resonance layer is a minimum distance allowed by a process of manufacturing the bottom electrode recess; the horizontal distance between the top electrode recess and the piezoelectric resonance layer is a minimum distance allowed by a process of manufacturing the top electrode recess.
26. The method of manufacturing a bulk acoustic wave resonator according to any one of claims 16 to 21 and 23 to 24, wherein a line width of the bottom electrode recess is a minimum line width allowed by a process of manufacturing the bottom electrode recess; the line width of the top electrode recess is the minimum line width allowed by the process of manufacturing the top electrode recess.
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| CN201910273070.7A CN111786653A (en) | 2019-04-04 | 2019-04-04 | Bulk acoustic wave resonator, method of manufacturing the same, filter, and radio frequency communication system |
| JP2021525685A JP7194474B2 (en) | 2019-04-04 | 2019-09-10 | Bulk acoustic wave resonator, manufacturing method thereof, filter, radio frequency communication system |
| PCT/CN2019/105087 WO2020199504A1 (en) | 2019-04-04 | 2019-09-10 | Bulk acoustic wave resonator and manufacturing method therefor, filter and radio frequency communication system |
| US17/449,836 US20220029603A1 (en) | 2019-04-04 | 2021-10-04 | Bulk acoustic wave resonator, filter and radio frequency communication system |
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