CN111786650A - 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 PDF

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Publication number
CN111786650A
CN111786650A CN201910272282.3A CN201910272282A CN111786650A CN 111786650 A CN111786650 A CN 111786650A CN 201910272282 A CN201910272282 A CN 201910272282A CN 111786650 A CN111786650 A CN 111786650A
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layer
top electrode
resonance
bottom electrode
electrode
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罗海龙
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Smic Ningbo Co ltd Shanghai Branch
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Smic Ningbo Co ltd Shanghai Branch
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Priority to CN201910272282.3A priority Critical patent/CN111786650A/en
Priority to PCT/CN2019/105091 priority patent/WO2020199507A1/en
Priority to JP2021525825A priority patent/JP7138988B2/en
Publication of CN111786650A publication Critical patent/CN111786650A/en
Priority to US17/449,836 priority patent/US12009803B2/en
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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 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
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric 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

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)

Abstract

The invention provides a bulk acoustic wave resonator, a manufacturing method thereof, a filter and a radio frequency communication system, wherein a top electrode sunken part which is formed at the periphery of a piezoelectric resonance layer and is 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

Bulk acoustic wave resonator, method of manufacturing the same, filter, and radio frequency communication system
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, and the part of the bottom electrode layer above the cavity extends flatly;
a piezoelectric resonance layer formed on a portion of the bottom electrode layer above the cavity;
and the top electrode layer is formed on the piezoelectric resonance layer and is provided with a top electrode concave part, the top electrode concave part is positioned in the area of the cavity at the periphery of the piezoelectric resonance layer and is concave towards the direction close to the bottom surface of the cavity, and the top electrode concave part extends around the peripheral direction of the piezoelectric resonance layer.
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 with a flat top surface on a part of the substrate;
forming a bottom electrode layer on a part of the first sacrificial layer, wherein the part of the bottom electrode layer on the top surface of the first sacrificial layer is extended flatly;
forming a piezoelectric resonance layer on the bottom electrode layer, wherein the piezoelectric resonance layer exposes a part of the first sacrificial layer and a part of the bottom electrode layer;
forming a second sacrificial layer with a first groove in an exposed area around the piezoelectric resonance 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 first groove forms a top electrode recess;
and removing the second sacrificial layer and the first sacrificial layer, wherein a cavity is formed at the positions of the second sacrificial layer and the first sacrificial layer, and the top electrode concave part is positioned in the cavity region at the periphery of the piezoelectric resonance layer and extends around the peripheral direction of the piezoelectric resonance layer.
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 concave part of the top electrode suspended on the cavity at the periphery of the piezoelectric resonance layer and reflected back to the corresponding area of the piezoelectric resonance layer, and then the loss caused when the transverse wave propagates to the film layer at the periphery of the cavity is 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 top electrode sunken part and the bottom electrode layer have the parts of overlapping each other, also be the gap structure between the part of overlapping, can greatly reduced parasitic parameter from this to avoid top electrode layer and bottom electrode layer electric contact scheduling problem in the cavity region, can improve device reliability.
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 concave part surrounds the top electrode resonance part for a circle, and can block transverse waves from the periphery of the piezoelectric resonance layer in an all-around mode, and therefore good quality factors are obtained.
7. Bottom electrode resonance portion and bottom electrode overlap joint portion adopt same rete to form, and thick even, and top electrode depressed part, top electrode resonance portion and top electrode overlap joint portion adopt same rete to form, and thick even, can simplify technology from this, reduce cost, and because the membrane thickness of top electrode depressed part is the same basically with other parts of top electrode layer, consequently the cracked condition of top electrode depressed part can not appear, can improve the reliability of device.
8. The bottom electrode layer is flat in the regional part of cavity, can be favorable to improving the thickness homogeneity of the film in the active area on the one hand, and on the other hand is favorable to reducing the degree of difficulty of the sculpture technology when forming the piezoelectricity resonance layer, avoids appearing the remaining problem of piezoelectricity material sculpture because of the top surface of bottom electrode layer is uneven to reduce parasitic parameter.
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 2C are schematic top-view structural diagrams of bulk acoustic wave resonators according to other embodiments of the present invention.
Fig. 2D 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 4F 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 second groove; 102A-active working area; 102B-null area; 103-a first sacrificial layer; 104-bottom electrode layer (i.e. remaining bottom electrode material layer); 1040-bottom electrode lap; 1041-bottom electrode resonance part; 1042 — 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 first 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 second 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. 2D, 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 removing the 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 and a bottom electrode resonance part 1041 which are connected in sequence, the part of the bottom electrode layer 104 above the cavity 102 is extended flatly, that is, the top surface of the part of the bottom electrode lap 1040 above the cavity is flush with the top surface of the bottom electrode resonance part 1041, and the bottom surface of the part of the bottom electrode lap 1040 above the cavity is flush with the bottom surface of the bottom electrode resonance part 1041. The top electrode layer 108 includes a top electrode overlapping portion 1080, a top electrode recessed portion 1081 and a top electrode resonance portion 1082 which are connected in sequence, the bottom electrode resonance portion 1041 and the top electrode resonance portion 1082 are overlapped with the piezoelectric resonance layer 1051, the cavity 102 and a region corresponding to the overlapped bottom electrode resonance portion 1041, the piezoelectric resonance layer 1051 and the top electrode resonance portion 1082 form an effective working area 102A of the bulk acoustic wave resonator, a portion of the cavity 102 other than the effective working area 102A is an inactive area 102B, the piezoelectric resonance layer 1051 is located in the effective working area 102A and separated from a film layer 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, the influence of the film layer around the cavity on longitudinal vibration generated by the piezoelectric resonance layer can be reduced, parasitic parameters generated in the inactive area 102B can be reduced, and device performance can be improved. The bottom electrode resonance portion 1041, the piezoelectric resonance layer 1051, and the top electrode resonance portion 1082 are flat structures whose upper and lower surfaces are planar, and the top electrode recess portion 1081 is located above the cavity 102B at the periphery of the active region 102A, electrically connected to the top electrode resonance portion 1082, and recessed toward a direction close to the bottom surface of the cavity 102. The top electrode recess portion 1081 is recessed downward as a whole with respect to the top surface of the top electrode resonance portion 1082 and is located in the cavity region (i.e., 102B) at the periphery of the piezoelectric resonance layer 1051. The top electrode recess 1081 may be a solid structure, or may be a hollow structure, preferably a hollow structure, so as to make the film thickness of the top electrode layer 108 uniform, and avoid the solid top electrode recess 1081 from causing the deformation of the top electrode resonance portion 1082, the piezoelectric resonance layer 1051 below the top electrode resonance portion, and the bottom electrode resonance portion 1041, thereby further improving the resonance factor. The bottom electrode resonance part 1041 and the top electrode resonance part 1082 are polygonal (both the top surface and the bottom surface are polygonal), and the shapes of the bottom electrode resonance part 1041 and the top electrode resonance part 1082 may be similar (as shown in fig. 2A and 2C) or identical (as shown in fig. 1A and 2B). The piezoelectric resonance layer 1051 has a polygonal structure similar to the shapes of the bottom electrode resonance portion 1041 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 layer structure in a shape of a "watch", a corner of the bottom electrode overlap portion 1040 and the bottom electrode resonance portion 1041 is aligned, a corner of the top electrode overlap portion 1080 and the top electrode resonance portion 1082 is aligned, the bottom electrode overlap portion 1040 and the top electrode overlap portion 1080 correspond to two bands of the "watch", the top electrode recess portion 1081 is disposed along an edge of the top electrode resonance portion 1082 and is only disposed in a region where the top electrode overlap portion 1080 and the top electrode resonance portion 1082 are aligned, the top electrode recess portion 1081 corresponds to a connection structure between a dial of the "watch" and a band, a stacked structure of the bottom electrode resonance portion 1041, the piezoelectric resonance layer 1051, and the top electrode resonance portion 1082 in the active region 102A corresponds to a film layer of the watch, the watch dial is connected to a film layer on a substrate around the cavity except for a band portion, the remaining portion is separated from the film layer on the substrate around the cavity by the cavity. That is, in this embodiment, the top electrode recess 1081 extends around the peripheral direction of the piezoelectric resonance layer 1051, and the top electrode recess 1081 only surrounds a part of the edge of the piezoelectric resonance layer 1051 along the peripheral direction of the piezoelectric resonance layer 1051, and with reference to the plane where the piezoelectric resonance layer 1051 is located, the top electrode recess 1081 and the bottom electrode overlapping portion 1040 partially surround two sides of the piezoelectric resonance layer 1051 and are opposite to each other, so that while a certain transverse wave blocking effect is achieved, the reduction of the area of the inactive area 102B not covered by the top electrode overlapping portion 1080 and the bottom electrode overlapping portion 1040 can be facilitated, and further the reduction of the device size is facilitated, and the reduction of the area of the top electrode overlapping portion 1080 and the bottom electrode overlapping portion 1040 is facilitated, so as to further reduce parasitic parameters and improve the electrical performance of the device. The bottom electrode overlapping portion 1040 is electrically connected to one side of the bottom electrode resonance portion 1041, and extends from the bottom electrode resonance portion 1041 to the upper portion 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 bottom electrode resonance 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 used to connect to a corresponding signal line to transmit a corresponding signal to the bottom electrode resonance portion 1041, the top electrode strap 1080 may be used to connect to a corresponding signal line, to transmit a corresponding signal to the top electrode resonance portion 1082 through the top electrode recess portion 1081, so that the bulk acoustic wave resonator can normally operate, specifically, a longitudinally extended mode or a "piston" mode is excited by applying a time-varying voltage to the bottom electrode resonance portion 1041 and the top electrode resonance portion 1082 through the bottom electrode strap portion 1040 and the top electrode strap portion 1080, respectively, the piezoelectric resonance layer 1051 converts energy in the form of electric energy into a longitudinal wave, in the process, parasitic transverse waves are generated, and the top electrode concave portion 1081 can prevent the transverse waves from being transmitted to the film layer on the periphery of the cavity and limit the transverse waves in the area of the cavity 102, so that energy loss caused by the transverse waves is avoided, and the quality factor is improved.
Preferably, the line widths of the top electrode recess portions 1081 are respectively the minimum line widths allowed by the corresponding processes, and the horizontal distances between the top electrode recess portions 1081 and the piezoelectric resonance layers 1051 are the minimum distances allowed by the corresponding processes, so that the top electrode recess portions 1081 can achieve a certain transverse wave blocking effect, and at the same time, the reduction of the device area can be facilitated.
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 angles α 1 and α 2 between the two side walls of the top electrode recess 1081 and the top surface of the piezoelectric resonance layer 1051 are both equal to or less than 45 degrees, so that the top electrode recess 1081 is prevented from being broken due to the fact that the side wall of the top electrode recess 1081 is too vertical, the effect of transmitting signals to the top electrode resonance portion 1082 is further affected, and meanwhile, the thickness uniformity of the whole top electrode layer 108 can be improved.
In a preferred embodiment of the present invention, the bottom electrode resonance portion 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 portion 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 1041 and the bottom electrode overlapping portion 1040 are integrally formed, and the top electrode resonance portion 1082, the top electrode recess portion 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 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 portion 1081 and the top electrode overlapping portion 1080 can respectively use any suitable conductive materials or semiconductor materials known in the art, 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), and the semiconductor material may be Si, Ge, SiGe, SiC, SiGeC, or the like. In other embodiments of the present invention, the bottom electrode resonance portion 1041 and the bottom electrode overlapping portion 1040 may be formed by different film layer manufacturing processes, and the top electrode resonance portion 1082, the top electrode recess 1081, and the top electrode overlapping portion 1080 may be formed by different film layer manufacturing processes, as the process cost and the process technology allow.
Referring to fig. 2A to 2C, in order to further improve the transverse wave blocking effect, the top electrode recess portion 1081 extends to more continuous sides of the top electrode resonance portion 1082. For example, referring to fig. 2A, the piezoelectric resonance layer 1051, the top electrode resonance portion 1082 and the bottom electrode resonance portion 1041 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 1041 is the largest, the top electrode recess portion 1081 is disposed along and connected to a plurality of sides 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 the projection of the portion of the bottom electrode resonance portion 1041 connected with the bottom electrode overlapping portion 1040 on the bottom surface of the cavity 102, so that the top electrode recess portion 1081 and the bottom electrode overlapping portion 1040 do not overlap, and the parasitic parameters can be reduced. For another example, referring to fig. 2B, the piezoelectric resonance layer 1051, the top electrode resonance portion 1082, and the bottom electrode resonance portion 1041 are all pentagonal planar structures, the area of the piezoelectric resonance layer 1051 is the smallest, the areas, shapes, etc. of the top electrode resonance portion 1082 and the bottom electrode resonance portion 1041 are the same or substantially the same, the top electrode recess 1081 surrounds a circumference of the top electrode resonance portion 1082, and the projections of the top electrode resonance portion 1082 and the bottom electrode resonance portion 1041 on the bottom surface of the cavity 102 are overlapped, so that the transverse wave generated by the piezoelectric resonance layer 1051 can be blocked in all directions by the closed ring-shaped DE top electrode recess 1081.
Referring to fig. 2A to 2C, in the embodiments of the present invention, the bottom electrode strap 1040 is electrically connected to at least one edge or at least one corner of the bottom electrode resonance portion 1041, and extends from the corresponding edge of the bottom electrode resonance portion 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 resonance portion 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 2B, the bottom electrode strap 1040 may extend only above a portion of the substrate at one side periphery of the cavity 102, the top electrode strap 1080 extends only above a portion of the substrate at one side periphery of the cavity 102, and 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, so as to avoid introducing parasitic parameters and possibly causing problems such as leakage and short circuit when the top electrode strap 1080 and the bottom electrode strap 1040 are overlapped. Preferably, however, referring to fig. 2C, the bottom electrode strap 1040 is disposed along all sides of the bottom electrode resonance portion 1041 and extends continuously to the substrate at the periphery of the cavity 102, so that the bottom electrode strap 1040 can extend to the upper side of the substrate at more directions at the periphery of the cavity 102, that is, at this time, the bottom electrode strap 1040 completely covers the cavity 102 above the cavity portion where it is located, so that the supporting force for the film layer of the effective working area 102A can be enhanced by laying the bottom electrode strap 1040 with a large area, and the cavity 102 is prevented 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 1080 from being disposed vertically with the bottom electrode strap 1040 and the like structure And excessive parasitic parameters are introduced due to the overlapping, so that the electrical performance and the reliability of the device can be further improved.
In various embodiments of the present invention, when the cavity 102 has a polygonal top view shape, the bottom electrode strap 1040 and the top electrode strap 1080 respectively expose at least one side of the cavity, so that at least one end of each of the bottom electrode resonance part 1041 connected to the bottom electrode strap 1040 and the top electrode resonance part 1082 connected to the top electrode recess 1081 is completely suspended, which may be beneficial to reduce the area of the inactive area 102B, further reduce parasitic parameters such as parasitic capacitance generated in the inactive area 102B, and improve device performance. Preferably, the top electrode recessed portion 1081 is staggered with respect to at least the bottom electrode overlapping portion 1040 above the cavity 102 (i.e. they do not overlap in the cavity region), so as to further reduce the parasitic parameters such as the parasitic capacitance generated in the inactive region 102B, thereby improving 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 is to the active region 102A, the better the line width of the top electrode recess 1081 is, preferably, the line width of the top electrode recess 1081 is the minimum line width allowed by the corresponding process, and the horizontal distance between the top electrode recess 1081 and the active region 102A (i.e., the piezoelectric resonance layer 1051) is the minimum distance allowed by the corresponding process.
It should be noted that, in the above embodiments, the top electrode resonance portion 1082 and the bottom electrode resonance portion 1041 have similar or identical shapes and have the same area, or the area of the bottom electrode resonance portion 1041 is larger than the area 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 1041 may not be similar, but preferably, the shape of the top electrode recess 1081 is 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 2C) of the invention, including:
s1, providing a substrate, and forming a first sacrificial layer with a flat top surface on a part of the substrate;
s2, forming a bottom electrode layer on a part of the first sacrificial layer, wherein the part of the bottom electrode layer on the top surface of the first sacrificial layer is extended flatly;
s3, forming a piezoelectric resonance layer on the bottom electrode layer, wherein the piezoelectric resonance layer exposes a part of the first sacrificial layer and a part of the bottom electrode layer;
s4, forming a second sacrificial layer with a first groove in the exposed area around the piezoelectric resonance layer;
s5, 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 first groove forms a top electrode recess;
and S6, removing the second sacrificial layer with the first groove and the first sacrificial layer, wherein a cavity is formed at the position of the second sacrificial layer with the first groove and the first sacrificial layer, and the top electrode recess is positioned in the cavity region at the periphery of the piezoelectric resonance layer and extends around the peripheral direction of the piezoelectric resonance 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 second groove and filling a material into the second 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 second groove 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 second 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 second groove 102 ' is rectangular, and in other embodiments of the present invention, the cross-section of the second groove 102 ' may be any other suitable shape, such as a circle, an ellipse, or other polygons (e.g., pentagon, hexagon, etc.) except for a rectangle.
Then, referring to fig. 1A, 1B and 4B, the first sacrificial layer 103 may be filled in the second groove 102' by processes of vapor deposition, thermal oxidation, spin coating or epitaxial growth, and the like, where the first sacrificial layer 103 may be selected from a semiconductor material, a dielectric material, a photoresist material, and the like different from the substrate 100 and the etching protection layer 101, for example, when the substrate 100 is a Si substrate, the first sacrificial layer 103 may be Ge, and the formed first sacrificial layer 103 may further cover the etching protection layer 101 at the periphery of the second groove or the top surface is higher than the top surface of the etching protection layer 101 at the periphery of the second groove; then, the top of the first sacrificial layer 103 is planarized to the top surface of the etching protection layer 101 by a Chemical Mechanical Planarization (CMP) process, so that the first sacrificial layer 103 is only located in the second groove 102', and the top surface of the first sacrificial layer 103 is flush with the top surface of the etching protection layer 101 around the first sacrificial layer 103, thereby providing a flat process surface for the subsequent formation of the bottom electrode layer 104 with a flat surface.
Referring to fig. 1A, 1B and 4C, in step S2, first, a bottom electrode material layer (not shown) may be covered on the surfaces of the etching protection layer 101 and the first sacrificial layer 103 by a suitable method according to the material of the bottom electrode to be formed, for example, the bottom electrode material layer may be formed by physical vapor deposition such as magnetron sputtering and evaporation, or chemical vapor deposition; 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 (the remaining bottom electrode material layer) 104 includes a bottom electrode resonance portion 1041 covering the active working region 102A to be formed subsequently, a bottom electrode strap 1040 extending from one side of the bottom electrode resonance portion 1041 to the outer side of the second recess 102' through the surface of the first sacrificial layer 103, and a bottom electrode peripheral portion 1042 separated from the bottom electrode resonance portion 1041, where the bottom electrode peripheral portion 1042 may be connected to a side of the bottom electrode strap 1040 opposite to the bottom electrode resonance portion 1041 to serve as a metal contact of the bulk acoustic wave resonator to be formed in the area, or may be separated from the bottom electrode strap 1040 to serve as a part of the bottom electrode strap of the adjacent bulk acoustic wave resonator, and in other embodiments of the present invention, the bottom electrode peripheral portion 1042 may be omitted. The bottom electrode resonance portion 1041 may be pentagonal in top view shape, and in other embodiments of the present invention, may also be quadrilateral or hexagonal, and the bottom electrode overlapping portion 1040 is electrically connected to at least one side or at least one corner of the bottom electrode resonance portion 1041, and extends from the corresponding side of the bottom electrode resonance portion 1041 to the top surface of the partial etching protection layer 101 at the periphery of the second groove 102' through the top surface of the first sacrificial layer 103 outside the bottom electrode resonance portion 1041, and furthermore, since the top surface of the first sacrificial layer 103 is flush with the top surface of the etching protection layer 101 in this embodiment, the bottom electrode layer 104 may be formed to have a flush bottom surface and a flush top surface, and at this time, the bottom electrode layer 104 may extend flat in the global scope, that is, the bottom electrode resonance portion 1041 and the bottom electrode overlapping portion 1040 have a flush bottom surface and a flush top surface. Preferably, as shown in fig. 2C, the bottom electrode strap 1040 completely covers the cavity 102 above the cavity portion where it is located, and has no overlap with the top electrode strap 1080 in the width direction of the top electrode strap 1080, so as to improve the supporting force for the subsequent film layer and avoid the overlap with the top electrode strap 1080 to introduce unnecessary parasitic parameters. The bottom electrode resonance 1041 may serve as an input electrode or an output electrode that receives or provides an electrical signal such as a Radio Frequency (RF) signal.
Referring to fig. 1A, 1B and 4C, in step S3, first, the film can be deposited by any suitable method known to those skilled in the art, such as chemical vapor deposition, physical vapor deposition or atomic layer depositionA piezoelectric material layer 105; 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). Further, when the piezoelectric material layer 105 includes aluminum nitride (AlN), the piezoelectric material layer 105 may further include a transition metal, for example, 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, and the piezoelectric resonance layer 1051 is located on the bottom electrode resonance portion 1041, exposes the bottom electrode overlap portion 1040, and may completely cover or partially cover the bottom electrode resonance portion 1041. The shape of the piezoelectric resonance layer 1051 may be the same as or different from that of the bottom electrode resonance unit 1041, and the planar shape thereof may be pentagonal, or may be 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 resonator layer 1051 to expose a portion of the first sacrificial layer 103 above the bottom electrode strap 1040 and around the bottom electrode resonator portion 1041, 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 first 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 1042, while providing a relatively flat process surface for formation of a subsequent second sacrificial layer and a top electrode layer.
Referring to fig. 1A, 1B and 4D, in step S4, 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 utilize the top surface of the first sacrificial layer 103 as an etching stop point in the subsequent etching process for forming the first groove 107, thereby controlling the depth of the subsequently formed first groove 107; 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 first groove 107, and the shape, size, position, and the like of the first groove 107 determine the shape, size, position, and the like of a subsequently formed top electrode recess. Preferably, the side wall of the first 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 first 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 first groove 107 is the minimum line width allowed by the corresponding process, and the horizontal distance between the first 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 first groove 107 and the bottom electrode overlapping portion 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 first groove 107 stops in a certain thickness of the first sacrificial layer 103, to ensure that the transverse wave in the thickness of the piezoelectric resonance layer 1051 can be blocked.
In other embodiments of the present invention, the second sacrificial layer 106 includes a first sub-sacrificial layer (not shown) and a second sub-sacrificial layer (not shown) which are made of different materials and stacked from bottom to top, and the arrangement of the first sub-sacrificial layer and the second sub-sacrificial layer enables a stop point of etching to be precisely controlled when a first groove is formed by etching, so as to precisely control a recess depth of a subsequently formed top electrode recess 1081, and thus, a thickness of the second sub-sacrificial layer determines a recess depth of the subsequently formed top electrode recess 1081. Wherein the second sacrificial layer 106 having the first sub-sacrificial layer, the second sub-sacrificial layer and the first groove 107 may be formed by the following steps including: firstly, filling a first sub-sacrificial layer in a gap between the piezoelectric resonance layer 1051 and the piezoelectric peripheral portion 1050 by a vapor deposition or epitaxial growth process, wherein the first sub-sacrificial layer is selected from a material which can be processed by some processes and then converted into another material, in this embodiment, the first sub-sacrificial layer may be a semiconductor material, and is formed in the gap by a chemical vapor deposition process, and at this time, the first sub-sacrificial layer not only fills the gap between the piezoelectric resonance layer 1051 and the piezoelectric peripheral portion 1050, but also covers the upper surfaces of the piezoelectric resonance layer 1051 and the piezoelectric peripheral portion 1050; then, the top of the first sub-sacrificial layer is planarized to the top surfaces of piezoelectric resonance layer 1051 and piezoelectric peripheral portion 1050 by a Chemical Mechanical Planarization (CMP) process so that the first sub-sacrificial layer is located only in the gap between piezoelectric resonance layer 1051 and piezoelectric peripheral portion 1050; then, selecting a suitable surface modification treatment process according to the material of the first sub-sacrificial layer, for example, including at least one of oxidation treatment, nitridation treatment and ion implantation, and performing surface modification treatment on the top of the first sub-sacrificial layer to a certain thickness, so that the first sub-sacrificial layer with the certain thickness is converted into a second sub-sacrificial layer of another material, where the second sub-sacrificial layer and the remaining first sub-sacrificial layer below the second sub-sacrificial layer, which is not subjected to the surface modification treatment, form a second sacrificial layer 106 that fills up the gap between the piezoelectric resonance layer 1051 and the piezoelectric peripheral portion 1050, and the thickness of the second sub-sacrificial layer depends on the recess depth of a top electrode recess 1081 to be formed subsequently; thereafter, since the surface treatment process may make the top surface of the filled second sacrificial layer 106 no longer flush with the top surface of the piezoelectric resonator layer 1051 around the filled second sacrificial layer, which is not favorable for the deposition of the subsequent top electrode layer 108, it is necessary to further planarize the top of the second sub-sacrificial layer to the top surface of the piezoelectric resonator layer 1051 through a Chemical Mechanical Planarization (CMP) process, so that the top surface of the second sacrificial layer 106 is flush with the top surface of the piezoelectric resonator layer 1051 around the filled second sacrificial layer again, so as to provide a relatively flat operation surface for the subsequent process. Then, the second sub-sacrificial layer in the periphery of the second sacrificial layer 106 corresponding to the effective working area (e.g., 102A in fig. 4F) of the bulk acoustic wave resonator to be manufactured may be etched by a process of photolithography and etching, and the etching may be stopped at the top surface of the first sub-sacrificial layer, or may be performed with a certain over-etching so as to be stopped in the first sub-sacrificial layer, thereby forming the first groove 107.
Referring to fig. 1A, fig. 1B and fig. 4E, in step S5, 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 first groove 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 first groove 107, a top electrode lap 1080 extending from the top electrode recess 1081 through a part of the top surface of the second sacrificial layer 106 to the piezoelectric peripheral portion 1050 outside the top electrode recess 1081, 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 1041, thereby facilitating reduction of the device size and reduction of 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 1041 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. 2B and 2C), 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). 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 second 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 second groove 102'. In an embodiment of the invention, referring to fig. 1A and fig. 2A, in a direction perpendicular to the bottom surface of the second groove 102', the top electrode recess 1081 and the bottom electrode overlapping portion 1040 do not overlap with each other at an edge facing the bottom electrode resonance portion 1041. The projections of the top electrode strap 1080 and the bottom electrode strap 1040 on the bottom surface of the second 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 second recess 102'.
Referring to fig. 1A, 1B and 4F, in step S6, a hole may be punched at an edge of the piezoelectric peripheral portion 1050 facing the second 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 at least one release hole (not shown) capable of exposing a portion of the first sacrificial layer 103 or a portion of the second sacrificial layer 106; then, gas and/or liquid medicine is introduced into the release hole to remove the second sacrificial layer 106 and the first sacrificial layer 103, and the second recess is emptied again to form the cavity 102, where the cavity 102 includes the space of the second recess 102' and the space under the top electrode recess 1081, which is occupied by the second sacrificial layer 106. Among them, the bottom electrode resonance portion 1041, 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 1041, the piezoelectric resonance layer 1051, the top electrode resonance portion 1082, and the cavity 102 overlap each other in the 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 1041 and the top electrode resonance portion 1082, vibration and resonance are generated in the thickness direction (i.e., the 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 the electric power is applied to the bottom electrode layer 108 and the top electrode layer 104, no resonance is generated due to the piezoelectric phenomenon. The independent acoustic thin film composed of the bottom electrode resonance portion 1041, 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 1041, 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 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, resulting in an improvement in the quality factor of the resonator and ultimately enabling an improvement in device performance.
It should be noted that the step S6 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 S6 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 second recess 102 'and filling the second recess 102', so that the cavity 102 formed in step S6 is a groove structure with the entire bottom recessed in the substrate, but the technical solution of the present invention is not limited thereto, in step S1 of other embodiments of the present invention, the first sacrificial layer 103 protruding over the substrate as a whole may also be formed by film deposition in combination with photolithography and etching processes, so that the cavity 102 formed in step S6 is a cavity structure protruding on the surface of the substrate as a whole, specifically, referring to fig. 2D and 5, in step S1, the second groove 102' for making the cavity 102 is no longer formed in the provided substrate, covering a first sacrificial layer 103 on the etching protection layer 101 on the surface of the substrate 100; then, the first sacrificial layer 103 is patterned by a process of photolithography and etching, only the first sacrificial layer 103 covering the region 102 remains, and the first sacrificial layer 103 is formed on a portion of the substrate, where the first sacrificial layer 103 may be a step structure with a narrow top and a wide bottom, a top surface of the first sacrificial layer 103 is flat, and a thickness of the first sacrificial layer 103 determines a depth of a subsequently formed cavity 102. In this embodiment, the subsequent steps are identical to those of the corresponding portions in the method of manufacturing the bulk acoustic wave resonator of the embodiment shown in fig. 4A to 4F, it is not repeated herein, except that the corresponding sidewalls of the bottom electrode peripheral portion 1043, the bottom electrode overlapping portion 1040, the piezoelectric peripheral portion 1050, the top electrode peripheral portion 1083, and the top electrode overlapping portion 1080 are formed to be deformed in conformity with the raised first sacrificial layer 103, and the longitudinal cross section of the bottom electrode layer 104 is changed to a "Z" shape, at this time, the portion of the bottom electrode layer 104 above the cavity 102 is extended flatly, that is, the bottom electrode strap 1040 is located above the cavity (excluding the portion corresponding to the sidewall of the first sacrificial layer 103) with its top surface flush with the top surface of the bottom electrode resonance portion 1041, and the bottom electrode strap 1040 is located above the cavity (excluding the portion corresponding to the sidewall of the first sacrificial layer 103) with its bottom surface flush with the bottom surface of the bottom electrode resonance portion 1041.
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 is manufactured together with the bottom electrode resonance portion, 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 (21)

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, and the part of the bottom electrode layer above the cavity extends flatly;
a piezoelectric resonance layer formed on a portion of the bottom electrode layer above the cavity;
and the top electrode layer is formed on the piezoelectric resonance layer and is provided with a top electrode concave part, the top electrode concave part is positioned in the area of the cavity at the periphery of the piezoelectric resonance layer and is concave towards the direction close to the bottom surface of the cavity, and the top electrode concave part extends around the peripheral direction of the piezoelectric resonance layer.
2. The bulk acoustic wave resonator according to claim 1, wherein the bottom electrode layer includes a bottom electrode resonance portion and a bottom electrode lap portion, the bottom electrode resonance portion having a flat top surface and overlapping the piezoelectric resonance layer, the bottom electrode lap portion extending flat from one side of the bottom electrode resonance portion to above a part of the substrate on the periphery of the cavity, the top electrode layer further including a top electrode resonance portion having a flat top surface and overlapping the piezoelectric resonance layer, and a top electrode lap portion extending in a peripheral direction around the top electrode resonance portion and connecting the top electrode resonance portion, the top electrode lap portion having one end connected to the top electrode lap portion and the other end lapped to 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 resonance portion and the top electrode resonance portion are each polygonal.
4. The bulk acoustic wave resonator according to claim 3, wherein the top electrode recess is provided along an edge of the top electrode resonance section at least in a region where the top electrode lap and the top electrode resonance section are aligned.
5. The bulk acoustic resonator according to claim 4, wherein the top electrode recess is offset from at least the bottom electrode lap above the cavity or the top electrode recess surrounds the top electrode resonance.
6. The bulk acoustic wave resonator according to claim 2, wherein the bottom electrode land and the bottom electrode resonance portion are formed using the same film layer, and the top electrode recess, the top electrode land and the top electrode resonance portion are formed using the same film layer.
7. The bulk acoustic wave resonator according to claim 3, wherein the bottom electrode lap completely covers the cavity above a portion of the cavity where the bottom electrode lap is located, and does not overlap with the top electrode lap in a width direction of the top electrode lap.
8. The bulk acoustic wave resonator according to any one of claims 1 to 7, wherein a 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.
9. The bulk acoustic wave resonator according to any one of claims 1 to 7, wherein a side wall of the top electrode recess is inclined with respect to a top surface of the piezoelectric resonance layer, and 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.
10. The bulk acoustic resonator according to any one of claims 1 to 7, wherein a line width of the top electrode recess is a minimum line width allowed by a process of manufacturing the top electrode recess.
11. The bulk acoustic wave resonator according to any one of claims 1 to 7, wherein the cavity is a second 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.
12. A filter comprising at least one bulk acoustic wave resonator according to any one of claims 1 to 11.
13. A radio frequency communication system comprising at least one filter according to claim 12.
14. A method of manufacturing a bulk acoustic wave resonator, comprising:
providing a substrate, and forming a first sacrificial layer with a flat top surface on a part of the substrate;
forming a bottom electrode layer on a part of the first sacrificial layer, wherein the part of the bottom electrode layer on the top surface of the first sacrificial layer is extended flatly;
forming a piezoelectric resonance layer on the bottom electrode layer, wherein the piezoelectric resonance layer exposes a part of the first sacrificial layer and a part of the bottom electrode layer;
forming a second sacrificial layer with a first groove in an exposed area around the piezoelectric resonance 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 first groove forms a top electrode recess;
and removing the second sacrificial layer and the first sacrificial layer, wherein a cavity is formed at the positions of the second sacrificial layer and the first sacrificial layer, and the top electrode concave part is positioned in the cavity region at the periphery of the piezoelectric resonance layer and extends around the peripheral direction of the piezoelectric resonance layer.
15. The method of fabricating a bulk acoustic wave resonator according to claim 14, wherein the step of forming a first sacrificial layer having a flat top surface on a portion of the substrate comprises: etching the substrate to form a second groove in the substrate; forming a first sacrificial layer to fill the second groove, and enabling the top surface of the first sacrificial layer to be flat; or,
the step of forming a first sacrificial layer on a portion of a substrate includes: covering a first sacrificial layer on the substrate and flattening the top surface of the first sacrificial layer; and patterning the first sacrificial layer to form a first sacrificial layer protruding from a part of the substrate.
16. The method of manufacturing a bulk acoustic wave resonator according to claim 14, wherein the step of removing the second sacrificial layer and the first sacrificial layer comprises:
after forming the top electrode layer, forming at least one release hole exposing at least a portion of the first sacrificial layer or a portion of the second sacrificial layer;
and introducing gas and/or liquid medicine into the release hole to remove the second sacrificial layer and the first sacrificial layer.
17. The method of manufacturing a bulk acoustic wave resonator according to claim 14, wherein the step of forming the bottom electrode layer includes: depositing a bottom electrode material layer to cover the first sacrificial layer and the substrate at the periphery of the first sacrificial layer; and patterning the bottom electrode material layer to form a bottom electrode lapping part and a bottom electrode resonance part which are sequentially connected, wherein the bottom electrode resonance part is overlapped with the piezoelectric resonance layer, one end of the bottom electrode lapping part is lapped on the substrate on the periphery of the cavity, and the top surface of the part of the bottom electrode lapping part, which is positioned in the cavity area, is flush with the bottom electrode resonance part.
18. The method of manufacturing a bulk acoustic wave resonator according to claim 17, wherein the step of forming the top electrode layer includes: depositing a top electrode material layer to cover the second sacrificial layer with the first 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.
19. The method of manufacturing a bulk acoustic wave resonator according to claim 18, wherein the bottom electrode resonance section and the top electrode resonance section are each polygonal, and the top electrode recess portion is provided along a side of the top electrode resonance section at least in a region where the top electrode lap section and the top electrode resonance section are aligned.
20. The method of manufacturing a bulk acoustic wave resonator according to claim 14, wherein a 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.
21. The method of manufacturing a bulk acoustic wave resonator according to claim 14, wherein a line width of the top electrode recess is a minimum line width allowed by a process of manufacturing the top electrode recess.
CN201910272282.3A 2019-04-04 2019-04-04 Bulk acoustic wave resonator, method of manufacturing the same, filter, and radio frequency communication system Pending CN111786650A (en)

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