CN116260420A

CN116260420A - Resonator, forming method thereof, filter and electronic equipment

Info

Publication number: CN116260420A
Application number: CN202111501562.0A
Authority: CN
Inventors: 李伟; 罗海龙; 黄河
Original assignee: Ningbo Semiconductor International Corp
Current assignee: Ningbo Semiconductor International Corp
Priority date: 2021-12-09
Filing date: 2021-12-09
Publication date: 2023-06-13

Abstract

A second substrate, a supporting layer, a first electrode, a first metal bonding layer and a second metal bonding layer in the resonator enclose a second cavity, and metal bonding is arranged between the first metal bonding layer and the second metal bonding layer, so that the first metal bonding layer and the second metal bonding layer are tightly combined.

Description

Resonator, forming method thereof, filter and electronic equipment

Technical Field

The present invention relates to the field of semiconductors, and more particularly, to a resonator, a method for forming the resonator, a filter, and an electronic device.

Background

Since the development of analog rf communication technology in the beginning of the last 90 th generation, rf front-end modules have gradually become the core components of communication devices. Among all the radio frequency front end modules, the filter has become the most powerful component of growth and development prospect. With the rapid development of wireless communication technology, the 5G communication protocol is mature, and the market also puts forward more strict standards on the performance of the radio frequency filter in all aspects. The performance of the filter is determined by the resonator elements that make up the filter. Among the existing filters, a Film Bulk Acoustic Resonator (FBAR) is one of the most suitable filters for 5G applications due to its small size, low insertion loss, large out-of-band rejection, high quality factor, high operating frequency, large power capacity, and good antistatic impact capability.

In general, a thin film bulk acoustic resonator includes two thin film electrodes, and a piezoelectric thin film layer is disposed between the two thin film electrodes, where the thin film electrodes and the piezoelectric thin film layer are used as a piezoelectric laminated structure, and the working principle is that the piezoelectric thin film layer is used to generate vibration under an alternating electric field, and the vibration excites bulk acoustic waves propagating along the thickness direction of the piezoelectric thin film layer, and the acoustic waves are transmitted to the interface between the upper electrode and the lower electrode and air and reflected back, and then reflected back and forth inside the thin film to form oscillation. Standing wave oscillation is formed when the acoustic wave propagates in the piezoelectric film layer just an odd multiple of half the wavelength.

In the thin film bulk acoustic resonator, a signal electrode penetrating one thin film electrode and a piezoelectric thin film layer and electrically connected to the other thin film electrode is formed on one side of the piezoelectric laminated structure, and the signal electrode is used for inputting and outputting signals of the piezoelectric laminated structure.

However, the device performance of the current resonator is not good, and the thin film bulk acoustic resonator cannot meet the requirement of a high-performance radio frequency system.

Disclosure of Invention

The invention solves the problem of providing a resonator, a forming method thereof, a filter and electronic equipment, and improves the performance of the resonator.

In order to solve the above problems, the present invention provides a resonator including: the piezoelectric lamination structure comprises a working area and a peripheral area surrounding the working area, wherein the piezoelectric lamination structure comprises a piezoelectric layer, a first electrode positioned on a first surface of the piezoelectric layer and a second electrode positioned on a second surface of the piezoelectric layer, and the first surface and the second surface are two opposite surfaces of the piezoelectric layer; the supporting layer is positioned at the peripheral area at one side of the second electrode and exposes the second electrode of the working area; a first metal bonding layer penetrating the piezoelectric stack structure of the peripheral region from one side of the first electrode and located on the support layer; a second substrate; the second metal bonding layer is positioned on the second substrate and provided with a first opening exposing the central area of the second substrate, one end of the second metal bonding layer, which is far away from the second substrate, is bonded on the first metal bonding layer, and a second cavity is formed by the second substrate, the supporting layer, the first electrode, the first metal bonding layer and the second metal bonding layer in a surrounding mode.

Correspondingly, the invention also provides a method for forming the resonator, which comprises the following steps: providing a piezoelectric laminated structure, wherein the piezoelectric laminated structure comprises a working area and a peripheral area surrounding the working area, the piezoelectric laminated structure comprises a piezoelectric layer, a first electrode positioned on a first surface of the piezoelectric layer and a second electrode positioned on a second surface of the piezoelectric layer, and the first surface and the second surface are two opposite surfaces of the piezoelectric layer; forming a supporting layer of the second electrode covering the peripheral region and exposing the working region from one side of the second electrode; forming a first metal bonding layer penetrating through the piezoelectric laminated structure of the peripheral region and positioned on the supporting layer from one side of the first electrode; providing a second substrate; forming a second metal bonding layer on the second substrate, the second metal bonding layer having a first opening exposing a central region of the second substrate; and aligning the first opening to the working area, bonding the second metal bonding layer with the first metal bonding layer, and enclosing a second cavity by the second substrate, the supporting layer, the first metal bonding layer of the first electrode and the second metal bonding layer.

Correspondingly, the invention further provides a filter comprising the filter.

Correspondingly, the invention further provides electronic equipment comprising the filter.

Compared with the prior art, the technical scheme of the invention has the following advantages:

in the resonator provided by the embodiment of the invention, the second substrate, the supporting layer, the first electrode, the first metal bonding layer and the second metal bonding layer enclose the second cavity, because the metal atoms in the first metal bonding layer and the second metal bonding layer are tightly arranged, the penetration of water vapor can be blocked, the capability of isolating external water vapor is strong, and even under a severe environment of high temperature and high humidity, the external water vapor is not easy to pass through the first metal bonding layer and the second metal bonding layer to enter the second cavity, so that the first electrode is not easy to react with the external water vapor to generate a first electrolyte solution, the corresponding first electrode is not easy to participate in primary cell reaction, the probability of the first electrode being oxidized is reduced, the thickness uniformity of the first electrode is higher, the first electrode can keep good conductive capability, the load caused by vibration of a piezoelectric lamination structure is reduced, the reliability of the resonator is favorable for improving the performance, and the resonator meets the requirement of a high-performance radio frequency system.

Drawings

FIG. 1 is a schematic diagram of a resonator;

fig. 2 to 16 are schematic structural views corresponding to each step in an embodiment of a method for forming a resonator according to the present invention.

Detailed Description

As known from the background art, the thin film bulk acoustic resonators (Film Bulk Acoustic Resonator, FBAR) are widely used. The reason for the poor performance of the device is analyzed by combining a resonator forming method.

The resonator includes: a piezoelectric stack structure, the piezoelectric stack structure comprising: a piezoelectric layer 2, a first electrode 1 located on a first side of the piezoelectric layer 2, and a second electrode 3 located on a second side of the piezoelectric layer 2; a first support layer 7 located on the surface of the first electrode 1, the first support layer 7 having a first opening therein; a first oxide layer 10 conformally covering the first support layer 7 and the first electrode 1 with the first opening exposed; a second substrate 9 bonded to the first support layer 7 through a first oxide layer 10 of the first support layer 7 away from the end face of the piezoelectric stack structure, wherein the second substrate 9, the first support layer 7 and the second electrode 1 enclose a second cavity 8; a signal input electrode 4 and a signal output electrode 5 penetrating the second electrode 3 and the piezoelectric layer 2 from one side of the second electrode 3 and electrically connected to the first electrode 1, the signal input electrode 4 and the signal output electrode 5 being located at the periphery of the second cavity 8; a second support layer 11 penetrating the piezoelectric laminated structure is positioned on the first support layer 7 of the signal input electrode 4 and the signal output electrode 5 away from the second cavity 8. In general, the material of the second electrode 3 is molybdenum, the material of the signal input electrode 4 and the signal output electrode 5 is copper, in a severe environment with high temperature and high humidity, external water vapor reacts with the signal input electrode 4 and the signal output electrode 5 to form a first electrolyte solution, external water vapor reacts with the second electrode 3 to form a second electrolyte solution, because the second electrode 3 contacts with both the signal input electrode 4 and the signal output electrode 5, a galvanic reaction occurs between the signal input electrode 4 and the signal output electrode 5 and the second electrode 3, and the surface of the second electrode 3 is oxidized, so that the thickness uniformity of the first electrode 3 is poor and the conductivity is poor, the load is easily caused to the vibration of the piezoelectric laminated structure, the reliability of the performance of the resonator is not improved, and the resonator cannot meet the requirements of a high-performance radio frequency system.

In order that the above objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.

Fig. 2 to 20 are schematic structural views corresponding to each step in an embodiment of a method for forming a resonator according to the present invention.

Referring to fig. 2, a piezoelectric stack 102 is provided, the piezoelectric stack 102 comprising a working area I and a peripheral area II surrounding the working area I, the piezoelectric stack 102 comprising a piezoelectric layer 105, a first electrode 104 on a first side of the piezoelectric layer 105 and a second electrode 106 on a second side of the piezoelectric layer 105, the first and second sides being opposite sides of the piezoelectric layer 105.

The piezoelectric stacks 102 provide for subsequent resonator formation, and the corresponding piezoelectric stacks 102 are used to effect a mutual conversion between an electrical signal and an acoustic signal, thereby enabling the filter to filter the signal.

The material of the first electrode 104 is a conductive material. The conductive material may be a metal material having conductive properties, for example: mo, al, cu, pt, au, ir, os, re, pd, rh, ru, mo and W.

The piezoelectric layer 105 is made of a piezoelectric material, and the piezoelectric material has a piezoelectric effect, that is, the piezoelectric material is a crystal material that generates voltage between two end surfaces when being subjected to pressure, and the piezoelectric effect of the piezoelectric material can be used to realize mutual conversion between mechanical vibration (sound wave) and alternating current, so as to realize conversion between sound energy and electric energy. The material of the piezoelectric layer 105 may be a piezoelectric material having a wurtzite-type crystal structure such as ZnO, alN, gaN, aluminum zirconate titanate, or lead titanate. In this embodiment, the material of the piezoelectric layer 105 is AlN. In this embodiment, the piezoelectric layer 105 may be formed by a deposition process such as a chemical vapor deposition process (Chemical Vapor Deposition, CVD), a physical vapor deposition process (Physical Vapor Deposition, PVD), or an atomic layer deposition process (Atomic Layer Deposition, ALD).

The material of the second electrode 106 is a conductive material. The conductive material may be a metal material having conductive properties, for example: mo, al, cu, pt, au, ir, os, re, pd, rh, ru, mo and W.

The method for forming the resonator comprises the following steps: providing a temporary substrate 100; the step of providing the piezoelectric stack 102 includes: forming a first electrode 104 on the temporary substrate 100; forming a piezoelectric layer 105 on the first electrode 104; a second electrode 106 is formed on the piezoelectric layer 105, and the first electrode 104, the piezoelectric layer 105, and the second electrode 106 function as the piezoelectric stack structure 102.

In this embodiment, the temporary substrate may be any suitable semiconductor substrate, such as a bulk silicon substrate, which may also be at least one of the following mentioned materials: siGe, sic, siGeC, tnAs, gaAs, inp or other group III and V compound semiconductors, and also include multilayer structures of these semiconductors, or ceramic substrates, quartz or glass substrates, etc. such as silicon-on-insulator (SOI), silicon-on-insulator (SSOI), silicon-on-insulator (S-SiGeOI), silicon-on-insulator (SiGeO 1), and germanium-on-insulator (GeOI), or double-sided polished silicon wafers (Double Side Polished Wafers, DSP), and alumina, etc.

It should be noted that, the method for forming the resonator further includes: after the temporary substrate 100 is provided, the first buffer layer 101 is formed on the temporary substrate 100 before the piezoelectric stack structure 102 is provided.

The first buffer layer 101 is used to improve the interface quality of the surface of the temporary substrate 100, and serves as a buffer between the first electrode 104 and the temporary substrate 100, improving the growth uniformity of the first electrode 104, and the adhesion between the temporary substrate 100 and the first electrode 104. The method for forming the subsequent resonator further comprises the following steps: the temporary substrate 100 is removed, and the first buffer layer 101 is used as a stop layer in the step of removing the temporary substrate 100, so that the difficulty in removing the temporary substrate 100 is reduced, and the influence of the subsequent process for removing the temporary substrate 100 on the first electrode 104 is prevented.

The material of the first buffer layer 101 may be one or more of silicon oxide, silicon nitride, and silicon oxynitride. In this embodiment, the material of the first buffer layer 101 is silicon oxide. In this embodiment, the first buffer layer 101 is formed by a deposition process. Specifically, the deposition process may be a chemical vapor deposition process or an atomic layer deposition process, or the like.

Referring to fig. 3, from the second electrode 106 side, a support layer 111 of the second electrode 106 is formed to cover the peripheral region II and expose the working region I.

The support layer 111 provides for subsequent bonding of the first substrate.

In this embodiment, the supporting layer 111 has a second opening 110, and the second opening 110 exposes the second electrode 106 of the working area I.

In this embodiment, the support layer 111 includes a filler layer 113, an etch stop layer 114, and a second buffer layer 115 in this order in a direction away from the piezoelectric stack structure 102.

In this embodiment, the material of the second buffer layer 115 includes tetraethyl orthosilicate (TEOS). In other embodiments, the material of the second buffer layer includes: and (3) silicon oxide. In this embodiment, the material of the etch stop layer 114 includes, but is not limited to, silicon nitride and silicon oxynitride. In this embodiment, the material of the filling layer 113 includes: tetraethyl orthosilicate (TEOS), silicon oxide, silicon nitride, aluminum oxide, and aluminum nitride.

In this embodiment, the bottom surface of the second opening 110 may be rectangular or polygonal other than rectangular, such as pentagonal, hexagonal, octagonal, etc., and may be circular or elliptical. In other embodiments, the longitudinal cross-sectional shape of the second opening may also be a spherical cap with a wider top and a narrower bottom, i.e. the longitudinal cross-section of the second opening is U-shaped.

The method for forming the resonator further comprises the following steps: after forming the second opening 110, the second electrode 106 is etched near a partial region of the support layer 111, forming a bottom air trench (Bottom Air Trench, BAT) 125 exposing the piezoelectric layer 105.

The step of forming the bottom air slot 125 includes: forming a first shielding layer (not shown) filling the second opening 110, the first shielding layer exposing a partial region of the second electrode 106; the second electrode 106 is etched using the first blocking layer as a mask to form a bottom air groove 125 exposing the piezoelectric layer 105.

The bottom air slot 125 is used to laterally reflect the sound wave, thereby facilitating the increase of the residence time of the sound wave in the cavity, thereby reducing the dissipation of energy, and correspondingly facilitating the increase of the acoustic-electric conversion performance of the resonator.

In this embodiment, the first shielding layer includes an organic material layer. Correspondingly, a spin coating process is adopted to form the first shielding layer.

In this embodiment, the first shielding layer is used as a mask to etch the second electrode 106 in a partial area exposed by the second opening 110 by using a dry etching process, so as to form a bottom air groove 125 penetrating the second electrode and exposing the piezoelectric layer 105. The dry etching process is an anisotropic etching process, so that the bottom air groove 125 has better etching profile controllability, and the shape of the bottom air groove 125 can meet the process requirement.

The method for forming the resonator further comprises the following steps: after the bottom air groove 125 is formed, the first shielding layer is removed.

The method for forming the resonator further comprises the following steps: after the bottom air groove 125 is formed, the protective layer 103 is formed on the end surface of the support layer 111 facing away from the piezoelectric stack structure 102, the side wall of the support layer 111, and the second electrode 106 where the support layer 111 is exposed.

The protective layer 103 is used to prepare for subsequent bonding of the first substrate at the end face of the support layer 111 facing away from the piezoelectric stack 102. The protective layer 103 is further used for blocking the second electrode 106 exposed from the second opening 110 from external water vapor, so that the surface of the second electrode 106 is not easily oxidized, the thickness uniformity of the first electrode is higher, the load formed by vibrating the piezoelectric laminated structure 102 is reduced, good conductivity is maintained, the reliability of the performance of the resonator is improved, and the resonator meets the requirement of a high-performance radio frequency system. In addition, because the protective layer 103, when the resonator works, the vibration frequency of the protective layer increases along with the increase of the working temperature, so that the decrease of the vibration frequency of the piezoelectric layer 105 can be compensated to a certain extent, the vibration frequency of the piezoelectric laminated structure 102 and the protective layer 103 as a whole is not easy to decrease too much, the effect of improving the temperature drift coefficient of the piezoelectric resonator is achieved, and the reliability of the performance of the resonator is improved.

The material of the protective layer 103 includes: one or more of tetraethyl orthosilicate (TEOS), silicon oxide, and silicon nitride. In this embodiment, the passivation layer 103 is formed by a chemical vapor deposition process.

It should be noted that, the surface of the second electrode 106 of the first cavity 123 is further formed with an edge convex structure 131 (Frame) surrounding the working area I, so as to change the acoustic impedance of the edge, prevent the energy of the working area from leaking out, and improve the quality factor of the resonator. Accordingly, the protective layer 103 covers the edge bump structure 131.

In this embodiment, the material of the edge bump structure 131 may be the same as that of the second electrode 106, and in other embodiments, the material of the edge bump structure may be different from that of the second electrode.

As an example, when the material of the edge bump structure 131 and the second electrode 106 is the same, the edge bump structure 131 and the second electrode 106 may be formed by etching the same material, and the respective edge bump structure 131 and second electrode 106 are a unitary structure.

Referring to fig. 4, a first substrate 112 is provided; the first substrate 112 is bonded on the support layer 111, and the first substrate 112, the second electrode 106, and the support layer 111 define a first cavity 123.

The first cavity 123 is advantageous in reducing vibration energy loss of the resonator, and can improve the acoustic-electric conversion performance of the resonator. The first substrate 112 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, germanium, silicon carbide, silicon germanium carbide, indium arsenide, gallium arsenide, indium phosphide, or other III/V compound semiconductors, and also include multilayer structures composed of these semiconductors, or are silicon on insulator, silicon on insulator laminate, silicon germanium on insulator, and germanium on insulator, or may be double-sided polished silicon wafers (Double Side Polished Wafers, DSP), or may be ceramic substrates such as alumina, quartz, or glass substrates, or the like.

The first substrate 112 is bonded to the protective layer 103 on the support layer 111.

Specifically, the contact surface between the protective layer 103 and the first substrate 112 is bonded by a covalent bond of si—o—si.

It should be noted that, the method for forming the resonator further includes: after the first cavity 123 is formed, the temporary substrate 100 and the first buffer layer 101 are removed. In this embodiment, the temporary substrate 100 may be removed by a thinning process or a peeling process.

In this embodiment, a process combining a dry process and a wet process is used to remove the first buffer layer 101. Specifically, a wet etching process is first used to remove a part of the first buffer layer 101 with a thickness, and after the part of the first buffer layer 101 with a thickness is removed, a dry etching process is used to remove the remaining first buffer layer 101. In the step of removing the remaining first buffer layer 101 by using the dry etching process, the difficulty of etching the first buffer layer 101 is greater than that of etching the first electrode 104, and the damage of the corresponding first electrode 104 is smaller.

Referring to fig. 5, the resonator forming method includes: after the piezoelectric stack 102 is provided, a partial region of the piezoelectric stack 102 in the peripheral region II is etched to form a peripheral groove 201 surrounding the working region I. The peripheral groove 201 provides a spatial location for a subsequently formed first metal bonding layer surrounding the piezoelectric stack 102.

In this embodiment, the piezoelectric stack structure 102 is etched by a dry etching process to form the peripheral groove 201. In the process of forming the peripheral groove 201, the top of the second buffer layer 115 is taken as an etching stop position, and accordingly, the peripheral groove 201 exposes the second buffer layer 115.

Referring to fig. 6 to 8, in the peripheral region II, a signal electrode penetrating the first electrode 104 and the piezoelectric layer 105 is formed from the side of the first electrode 104, the signal electrode being located on the second electrode 106.

And a signal electrode electrically connected to the second electrode 106.

The capability of the first metal bonding layer and the second metal bonding layer 303 for isolating external water vapor is stronger, even under the severe environment of high temperature and high humidity, the external water vapor is not easy to pass through the first metal bonding layer and the second metal bonding layer 303 and enter the second cavity, corresponding external water vapor is not easy to react with the signal electrode to generate a second electrolyte solution, the first electrode 104 is not easy to react with the external water vapor to generate the first electrolyte solution, so that the first electrode 104 is not easy to react with the signal electrode to generate a primary cell, the probability of oxidizing the first electrode 104 is reduced, the thickness uniformity of the first electrode 104 is higher, the load formed by vibrating the piezoelectric laminated structure 102 is reduced, and good conductive capability is maintained, so that the reliability of the performance of the resonator is improved, and the resonator meets the requirement of a high-performance radio frequency system.

Specifically, the signal electrodes include a first signal electrode 118 and a second signal electrode 119 (as shown in fig. 8), and the signal electrodes are located on the second electrode 106, so that the signal electrodes are electrically connected to the second electrode 106, and the first signal electrode 118 and the second signal electrode 119 are used for inputting and outputting signals, respectively, when the resonator is in operation.

In this embodiment, the material of the first signal electrode 118 and the second signal electrode 119 is copper. In other embodiments, the first signal electrode and the second signal electrode may be made of other types of metal materials.

The step of forming the signal electrode includes: as shown in fig. 6, from the side of the piezoelectric stack structure 102 away from the second electrode 106, the first electrode 104 and the piezoelectric layer 105 of the peripheral region II are etched to form a first trench 116 and a second trench 117 exposing the second electrode 106, the first trench 116 and the second trench 117 being spaced apart; as shown in fig. 7, an organic layer is formed on the peripheral groove, the first trench 116, the second trench 117, and the first electrode 104, the organic layer exposing the first trench 116, the second trench 117, and a partial region of the first electrode 104 layer adjacent to the first trench 116 and the second trench 117; as shown in fig. 7, a signal electrode is formed on the first trench 116, the second trench 117, and a partial region of the first electrode 104 layer adjacent to the first trench 116 and the second trench 117 where the organic layer is exposed.

Before forming the organic layer, a third seed layer 203 is formed to cover the peripheral groove 201, the first trench 116, the second trench 117, and the first electrode 104; in the step of forming the organic layer 120, the organic layer 120 is formed on the third seed layer 203; in the step of forming the signal electrode, a conductive material layer is formed on the third seed layer 203 where the organic layer 120 is exposed, the conductive material layer located in the first trench 116 serves as the first signal electrode 118, and the conductive material layer located in the second trench 117 serves as the second signal electrode 119.

In this embodiment, the first electrode 104 and the piezoelectric layer 105 are etched by a dry etching process, and the second electrode 106 is exposed to form a first trench 116 and a second trench 117. The dry etching process has anisotropic etching characteristics and good etching profile control, is favorable for enabling the shapes of the first groove 116 and the second groove 117 to meet the process requirements, and can take the top of the second electrode 106 as an etching stop position in the process of forming the first groove 116 and the second groove 117 by adopting the dry etching process.

In this embodiment, the first trench 116 and the second trench 117 can be used to define the edges of the resonator active area, i.e. the edges of the area where the resonator selects effective resonance.

In the step of forming the first trench 116 and the second trench 117, the first trench 116 and the second trench 117 are closer to the working area I than the peripheral groove 201.

The third seed layer 203 provides a good interface state for forming the conductive material layer. In this embodiment, the material of the third seed layer 203 includes copper. The material of the signal electrode includes copper, and the material of the third seed layer 203 includes copper, so that the conductive material layer formed by electroplating has high purity and few defects. The third seed layer 203 is formed using an atomic layer deposition process or a chemical vapor deposition process.

The organic layer 120 serves to define formation regions of the first and

second signal electrodes

118 and 119.

In this embodiment, the material of the organic layer 120 includes photoresist. The forming step of the organic layer 120 includes: forming a photoresist material layer covering the third seed layer 203; the photoresist material layer is patterned, and the generated photoresist material layer serves as the organic layer 120.

In this embodiment, the conductive material layer is formed by an electroplating process.

In the step of forming the signal electrode, the distance L1 from the bottom of the signal electrode to the working area I is not necessarily too small. If the distance L1 is too small, the bottom air slot 125 and the top air slot formed later will have smaller dimensions, and the effect of the transverse reflection of the sound wave will be poor, which will result in poor acoustic-electric conversion performance of the resonator and lower the quality factor of the resonator. In this embodiment, the distance L1 from the bottom of the signal electrode to the working area I is greater than 10 nm. Specifically, the distance L1 from the bottoms of the first signal electrode 118 and the second signal electrode 119 to the working area I is greater than 10 nm.

In this embodiment, too large a distance L1 from the bottom of the signal electrode to the working area I is not preferable, which may result in too large a chip size, wasting effective area, and being unfavorable for adapting to the miniaturization trend of the chip.

As shown in fig. 8, the method for forming the resonator further includes: after the first signal electrode 118 and the second signal electrode 119 are formed, the organic layer 120 is removed. The removal of the organic layer 120 provides for the subsequent formation of a first metal bonding layer in the peripheral trench 201.

In this embodiment, the material of the organic layer 120 is photoresist, and accordingly, ashing is used to remove the organic layer 120.

The method for forming the resonator further comprises the following steps: after the organic layer 120 is removed, the third seed layer 203 exposed by the first and

second signal electrodes

118 and 119 is also removed.

The third seed layer 203 exposed by the first signal electrode 118 and the second signal electrode 119 is removed in preparation for the subsequent formation of a top air trench.

In this embodiment, a wet etching process is used to remove the third seed layer 203 exposed by the signal electrode. The wet etching process has isotropic etching characteristics and higher etching rate. Specifically, the wet etching solution includes: hydrogen Fluoride (HF) or buffered oxide etching solutions (Buffered Oxide Etch, BOE).

As shown in fig. 9, the method for forming the resonator further includes: after forming the signal electrode, the first electrode 104 is etched in a partial region near the signal electrode, and a Top Air Trench (TAT) 126 is formed penetrating the first electrode 104 and exposing the piezoelectric layer 105.

The top air groove 126 is used for transversely reflecting the sound wave, so that the residence time of the sound wave in the second cavity formed later is improved, the dissipation of energy is reduced, and the sound-electricity conversion performance of the resonator is correspondingly improved. In addition, it should be noted that, after the top air slot 126 is formed, the range of the operating vibration frequency of the resonator can be tested, and the frequency modulation of the first electrode 104 with a partial thickness in the subsequent etching working area I is used as a reference.

In this embodiment, the top air slots 126 are formed using a dry etching process.

It should be noted that, the first signal electrode 118 and the second signal electrode 119 have a partial area located on the first electrode 104, and the corresponding first signal electrode 118 and second signal electrode 119 are electrically connected to the first electrode 104, and because the bottoms of the first signal electrode 118 and the second signal electrode 119 are electrically connected to the second electrode 106, the first signal electrode 118 makes the first electrode 104 and the second electrode 106 disconnected by the top air slot 126 at the same potential, and when the resonator works, the induced potential generated by the first electrode 104 on one side of the top air slot 126 far from the working area I is reduced, which is beneficial to reducing the influence of parasitic effects; similarly, the second signal electrode 119 makes the portion of the second electrode 106 disconnected by the bottom air groove 125 at the same potential as the first electrode 104, so that the induced potential generated by the second electrode 106 on the side of the bottom air groove 125 away from the working area I is reduced when the resonator is operated, which is beneficial to reducing the influence of parasitic effects.

Referring to fig. 10, the resonator forming method includes: after the signal electrode is formed, a portion of the thickness of the first electrode 104 in the working area I is etched.

The first electrode 104 with a partial thickness in the working area I is etched according to the working requirement of the resonator, the thickness of the first electrode 104 is reduced, and the vibration frequency of the piezoelectric stack structure 102 can be adjusted when the piezoelectric stack structure 102 works.

In this embodiment, an Ion Beam Etching (IBE) process is used to etch a portion of the thickness of the first electrode 104 in the working area I. The etching gas used in the ion beam etching process includes Ar.

It should be noted that, in the step of etching the first electrode 104 having a partial thickness in the working area I by using the ion beam etching process, the second buffer layer 115 having a partial thickness is also etched.

Referring to fig. 11, from the first electrode 104 side, a first metal bonding layer 301 (as shown in fig. 11) penetrating the piezoelectric stack structure 102 of the peripheral region II and located on the support layer 111 is formed.

The first metal bonding layer 301 is used for metal bonding with a second metal bonding layer formed later.

The step of forming the first metal bonding layer 301 penetrating the piezoelectric stack 102 of the peripheral region II and located on the support layer 111 includes: forming a mask layer 302 of a part of the peripheral groove 201 on the side of the piezoelectric stack structure 102 in the piezoelectric stack structure 102; a first metal bonding layer 301 is formed on the surface of the support layer 111 exposed by the mask layer 302.

The mask layer 302 is used to define a formation region of the first metal bonding layer 301. In this embodiment, the material of the mask layer 302 includes photoresist.

The forming step of the mask layer 302 includes: forming a photoresist material layer; the photoresist material layer is patterned and the resulting photoresist material layer serves as a mask layer 302.

It should be noted that, the mask layer 302 covers the mask layer 302 of a portion of the peripheral groove 201 on the side of the piezoelectric stack structure 102, that is, the mask layer 302 covers the sidewall of the signal electrode, which is advantageous to space the first metal bonding layer 301 formed from the signal electrode.

In this embodiment, the first metal bonding layer 301 is a composite laminate, and the step of forming the first metal bonding layer 301 in the peripheral groove 201 exposed by the mask layer 302 includes: forming a first metal layer 205 on the support layer 111; a second metal layer 206 is formed on the first metal layer 205, and the first metal layer 205 and the second metal layer 206 serve as a first metal bonding layer 301. In other embodiments, the first metal bonding layer may also be a single film layer.

In this embodiment, the first metal bonding layer 301 is composed of metal, and correspondingly, the metal atoms in the first metal bonding layer 301 are closely arranged, so that the first metal bonding layer 301 has higher compactness and has stronger permeation resistance compared with the dry film (dry film) with the network polymer structure as a component.

The materials of the first metal layer 205 include: copper, gold, aluminum, and titanium. The material of the first metal layer 205 comprises copper. Copper has good electrical and thermal conductivity and good process compatibility during semiconductor processing.

The melting point of the second metal layer 206 is smaller than that of the first metal layer 205, the second metal layer 206 is used as a bonding process layer, the second metal layer 206 has the advantage of low bonding temperature, and key devices and film layers such as the piezoelectric laminated structure 102 are not easy to damage in the process of bonding the second metal layer 206. Specifically, the material of the second metal layer 206 includes tin.

In this embodiment, the thickness of the first metal bonding layer 301 is 0.5um to 0.15um. If the thickness of the first metal bonding layer 301 is too large, the second metal layer 206 is easy to flow and overflow during the bonding process, resulting in deformation of the second cavity 304, which causes unnecessary load to the vibration of the piezoelectric stack structure 102, which is not beneficial to improving the reliability of the performance of the resonator, and the resonator cannot meet the requirements of the high performance rf system. If the thickness of the first metal bonding layer 301 is too small, the bonding strength between the first metal bonding layer 301 and the second metal bonding layer 303 is poor, external water vapor easily enters the second cavity 304 from between the first metal bonding layer 301 and the second metal bonding layer 303, the first electrode 104 easily reacts with the external water vapor to generate a first electrolyte solution, the corresponding first electrode 104 easily participates in the primary cell reaction, and the probability of oxidizing the first electrode 104 is increased, so that the thickness uniformity of the first electrode 104 is poor, the conductivity of the first electrode 104 is poor, the load caused by vibration of the piezoelectric lamination structure 102 is easy, the reliability of the performance of the resonator is not improved, and the resonator cannot meet the requirement of a high-performance radio frequency system.

In this embodiment, the first metal layer 205 is formed by an electroplating process. A second metal layer 206 is formed on the first metal layer 205 using an electroplating process. The electroplating process has the advantages of simple operation, high deposition speed, low price and the like.

In the step of forming the first metal bonding layer 301, the first metal bonding layer 301 is formed in the peripheral area II on the side of the signal electrode away from the working area I, and the first metal bonding layer 301 is spaced apart from the signal electrode.

The first metal bonding layer 301 is far away from the working area I compared with the signal electrode, so that the subsequently formed second cavity can encapsulate the signal electrode, isolate water vapor outside the second cavity, and therefore, in a high-temperature and high-humidity environment, the first signal electrode 118 and the second signal electrode 119 are not easy to react with the water vapor to generate a second electrolyte solution, and further, the first electrode 104, the first signal electrode 118 and the second signal electrode 119 are not easy to react with primary batteries, the probability of oxidizing the first electrode 104 is reduced, the thickness uniformity of the first electrode 104 is higher, the load of vibration of the piezoelectric laminated structure 102 is reduced, good conductive capacity is maintained, the reliability of the performance of the resonator is improved, and the resonator meets the requirement of a high-performance radio-frequency system.

In addition, the first metal bonding layer 301 is spaced from the signal electrode, specifically, the first metal bonding layer 301 is spaced from the first signal electrode 118 and the second signal electrode 119, so that when the resonator works, the first metal bonding layer 301 is prevented from interfering with signal transmission of the first signal electrode 118 and the second signal electrode 119, affecting the vibration frequency of the piezoelectric laminated structure 102, and reducing the quality factor of the resonator.

It should be noted that the step of forming the first metal bonding layer 301 further includes: prior to forming the mask layer 302, a first seed layer 204 is formed that conformally covers the peripheral groove 201, the signal electrode, and the piezoelectric stack 102.

The first seed layer 204 provides a good interface state for forming the first metal layer 205.

In this embodiment, the material of the first seed layer 204 includes copper. The material of the first metal layer 205 includes copper, and the material of the first seed layer 204 includes copper, so that the first metal layer 205 formed by electroplating has high purity and few defects. In this embodiment, the first seed layer 204 is formed by an atomic layer deposition process or a chemical vapor deposition process.

Accordingly, in the step of forming the first metal bonding layer 301, the first metal bonding layer 301 is formed on the first seed layer 204. The first metal bonding layer 301 has better formation quality with the first seed layer 204 as a growth basis.

In the step of forming the first metal bonding layer, the distance L2 between the first metal bonding layer 301 and the working area I is not necessarily too small. If the distance L2 is too small, the dimensions of the top air groove 126 and the bottom air groove 125 between the first metal bonding layer 301 and the working area I are smaller, the effect of transverse reflection on the sound wave is poor, the sound wave energy is easy to dissipate, the sound-electricity conversion performance of the resonator is poor and the stability is poor, in addition, the distance is too small, and the structural strength of the cavity is low. In this embodiment, the distance L2 from the first metal bonding layer 301 to the working area I is greater than 20 nm.

In this embodiment, too large a distance L2 from the first metal bonding layer 301 to the working area I is not desirable, and if the distance is too large, the chip size is too large, which wastes the effective area and is not beneficial to conform to the miniaturization trend of the chip.

It should be noted that the second metal bonding layer is bonded on the first metal bonding layer 301, and the distance between the corresponding second metal bonding layer and the working area I is greater than 20 nm.

Referring to fig. 12, the method of forming a resonator further includes: after the first metal bonding layer 301 is formed, the mask layer 302 is removed.

Removing the mask layer 302 provides for subsequent bonding of the first metal bonding layer 301 and the second metal bonding layer 302 to form a second cavity.

In this embodiment, the material of the mask layer 302 includes photoresist, and accordingly, ashing is used to remove the mask layer 302.

It should be noted that, the method for forming the resonator further includes: after the first metal bonding layer 301 is formed, the first seed layer 204 exposed from the first metal bonding layer 301 is removed.

Accordingly, the first seed layer 204 on the piezoelectric stack 102 is removed, so that the vibration load of the piezoelectric stack is prevented from being increased when the resonator works, the quality factor of the resonator is higher, the reliability of the performance of the resonator is improved, and the resonator meets the requirement of a high-performance radio frequency system.

In this embodiment, a wet etching process is used to remove the first seed layer 204 exposed by the first metal bonding layer 301. The wet etching process is an isotropic etching process, reduces the difficulty in removing the first seed layer 204 on the side wall of the signal electrode, and has the characteristic of high removal efficiency.

Referring to fig. 13, a second substrate 122 is provided; a second metal bonding layer 303 is formed on the second substrate 122, the second metal bonding layer 303 being for bonding with the first metal bonding layer 301, the second metal bonding layer 303 having a first opening 130 exposing a central region of the second substrate 122.

The second substrate 122 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, germanium, silicon carbide, silicon germanium carbide, indium arsenide, gallium arsenide, indium phosphide, or other III/V compound semiconductors, and also include multilayer structures composed of these semiconductors, or are silicon on insulator, laminated silicon germanium on insulator, and germanium on insulator, or may be double-sided polished silicon wafers, ceramic substrates such as alumina, quartz, or glass substrates, and the like.

In this embodiment, the second metal bonding layer 303 is a composite laminate, and the step of forming the second metal bonding layer 303 on the second substrate 122 includes the steps of: forming a first metal layer 205 on the second substrate 122; a second metal layer 206 is formed on the first metal layer 205, and the first metal layer 205 and the second metal layer 206 serve as a second metal bonding layer 303. In other embodiments, the second metal bonding layer may also be a single film layer.

In this embodiment, the second metal bonding layer 303 is composed of metal, and correspondingly, the metal atoms in the second metal bonding layer 303 are closely arranged, so that the second metal bonding layer 303 has higher compactness and has stronger permeation resistance compared with the dry film (dry film) with the mesh polymer structure as a component.

In this embodiment, the thickness of the second metal bonding layer 303 is 0.5um to 0.15um. If the thickness of the second metal bonding layer 303 is too large, the second metal layer 206 is easy to flow and overflow during the bonding process, resulting in deformation of the second cavity 304, which causes unnecessary load to the vibration of the piezoelectric stack structure 102, which is not beneficial to improving the reliability of the performance of the resonator, and the resonator cannot meet the requirements of the high performance rf system. If the thickness of the second metal bonding layer 303 is too small, the bonding strength between the second metal bonding layer 303 and the second metal bonding layer 303 is poor, external water vapor easily enters the second cavity 304 from between the second metal bonding layer 303 and the second metal bonding layer 303, the first electrode 104 easily reacts with the external water vapor to generate a first electrolyte solution, the corresponding first electrode 104 easily participates in the primary cell reaction, and the probability of oxidizing the first electrode 104 is increased, so that the thickness uniformity of the first electrode 104 is poor, the conductivity of the first electrode 104 is poor, the load caused by vibration of the piezoelectric lamination structure 102 is easy, the reliability of the performance of the resonator is not improved, and the resonator cannot meet the requirement of a high-performance radio frequency system.

In this embodiment, the first metal layer 205 is formed by an electroplating process. A second metal layer 206 is formed on the first metal layer 205 using an electroplating process.

The step of forming a second metal bonding layer on the second substrate 122 includes: forming a first metal layer 205 on the second substrate 122; a second metal layer 206 is formed on the first metal layer 205, and the first metal layer 205 and the second metal layer 206 serve as a second metal bonding layer 303.

In this embodiment, the first metal layer 205 is formed on the second substrate 122 by using an electroplating process, and the second metal layer 206 is formed on the first metal layer 205 by using an electroplating process. The electroplating process has the advantages of simple operation, high deposition speed, low price and the like.

In this embodiment, the first metal bonding layer 301 and the second metal bonding layer 303 are made of the same material, and each includes the first metal layer 205 and the second metal layer 206. Correspondingly, the forming process flow of the first metal bonding layer 301 and the second metal bonding layer 303 is the same, which is beneficial to simplifying the forming method of the resonator and saving the cost.

The method for forming the resonator further comprises the following steps: after providing the second substrate 122, before forming the second metal bonding layer 303 on the second substrate 122, forming a seed material layer on the second substrate 122; the seed material layer is patterned to form a second seed layer 306.

In this embodiment, the material of the second seed layer 306 includes copper. The material of the first metal layer 205 includes copper, and the material of the first seed layer 204 includes copper, so that the first metal layer 205 formed by electroplating has high purity and few defects. In this embodiment, an atomic layer deposition process or a chemical vapor deposition process is used to form the seed material layer.

In the step of forming the second metal bonding layer 303 on the second substrate 122, the second metal bonding layer 303 is formed on the second seed layer 306.

Referring to fig. 14, the first opening 130 is aligned to the working area I, so that the second metal bonding layer 303 is bonded to the first metal bonding layer 301, and the second substrate 122, the support layer 111, the first metal bonding layer 301 of the first electrode 104, and the second metal bonding layer 303 enclose a second cavity 304.

The second substrate 122, the supporting layer 111, the first electrode 104, the first metal bonding layer 301 and the second metal bonding layer 303 enclose a second cavity 304, and metal bonding is formed between the first metal bonding layer 301 and the second metal bonding layer 303, so that the first metal bonding layer 301 and the second metal bonding layer 303 are tightly combined, compared with a dry film, the capability of isolating external moisture of the first metal bonding layer 301 and the second metal bonding layer 303 is stronger, the external moisture is not easy to penetrate through the first metal bonding layer 301 and the second metal bonding layer 303 to enter the second cavity 304 even under a severe environment with high temperature and high humidity, the first electrode 104 is not easy to react with the external moisture to generate a first electrolyte solution, the first electrode 104 is not easy to participate in a primary cell reaction, the probability that the first electrode 104 is oxidized is reduced, the thickness uniformity of the first electrode 104 is higher, the load formed by vibration of the piezoelectric laminated structure 102 is reduced, good conductive capability is maintained, the reliability of the resonator performance is improved, and the high-performance requirement of the resonator is met.

The second cavity 304 is provided with a signal electrode for signal transmission, the first metal bonding layer 301 and the second metal bonding layer 303 have stronger capability of isolating external water vapor, the corresponding external water vapor is not easy to react with the signal electrode to generate a second electrolyte solution, the first electrode 104 is not easy to react with the external water vapor to generate a first electrolyte solution, and therefore the first electrode 104 is not easy to react with the signal electrode in a primary cell, and the probability of oxidizing the first electrode 104 is reduced.

In the step of bonding the second metal bonding layer 303 to the first metal bonding layer 301 in this embodiment, a metal bonding process is used to bond the first metal bonding layer 303 to the second metal bonding layer 301. The metal bonding process bonds the first metal bonding layer 301 and the second metal bonding layer 303 together by metal bonding, diffusion of metal of the bonding surface, or metal melting, or the like.

Specifically, the second metal layer 206 in the first metal bonding layer 301 and the second metal layer 206 in the second metal bonding layer 303 are bonded. The same material is easy to diffuse in the metal bonding process, so that the bonding effect between the first metal bonding layer 301 and the second metal bonding layer 303 is better.

The process parameters of the step of bonding the second metal bonding layer 301 to the first metal bonding layer 303 include: the bonding temperature is 240 ℃ to 300 ℃, the bonding pressure is 10KN to 50KN, and the chamber pressure is less than 10mTorr.

Specifically, the bonding temperature is not too high nor too low. If the bonding temperature is too high, the second metal layer 301 will have too high fluidity after melting, which will cause metal overflow, form an electrical short circuit, and easily cause the risk of deformation of the second cavity 304; in addition, excessive temperatures can cause degradation in the performance of the core device, resulting in poor reliability in the performance of the resonator, which cannot meet the requirements of high performance rf systems. If the bonding temperature is too low, the metal is not sufficiently melted, so that insufficient bonding force is caused or bonding gaps are formed, further reliability failure occurs, the reliability of the performance of the resonator is poor, and the resonator cannot meet the requirements of a high-performance radio frequency system.

Specifically, the bonding pressure is not too high nor too low. If the bonding pressure is too high, the first metal bonding layer 301 and the second metal bonding layer 303 are easy to deform, and the risk of deformation of the second cavity 304 is easy to occur, so that load is easily caused to vibration of the piezoelectric laminated structure. If the bonding pressure is too small, the bonding strength of the first metal bonding layer 301 and the second metal bonding layer 303 is weak, the bonding position of the first metal bonding layer 301 and the second metal bonding layer 303 is easy to leak external water vapor into the second cavity, so that the first electrode 104 is easy to react with the external water vapor to generate a first electrolyte solution, the signal electrode is easy to react with the external water vapor to mix with a second electrolyte solution, further, a galvanic reaction occurs between the signal electrode and the first electrode 104, the first electrode 104 is easy to oxidize, the thickness uniformity of the first electrode 104 is poor, good conductivity is maintained, the reliability of the performance of the resonator is reduced, and the resonator cannot meet the requirement of a high-performance radio frequency system.

Specifically, the environmental pressure is not too high, if the pressure is too high, metal extrusion overflows, short circuit is caused, and the height of the second cavity 304 is obviously reduced.

In this embodiment, the second cavity 304 is beneficial to reduce the vibration energy loss of the resonator, and can improve the acoustic-electric conversion performance of the resonator.

Specifically, the second cavity 304 is surrounded by the second substrate 122, the supporting layer 111, the first metal bonding layer 301 of the first electrode 104, and the second metal bonding layer 303.

It should be noted that, because the first trench 116 and the second trench 117 are closer to the working area I than the peripheral trench 201. Accordingly, the second cavity 304 can encapsulate the first signal electrode 118 and the second signal electrode 119 in the second cavity 304, and in a high-temperature and high-humidity environment, external water vapor is not easy to react with the first signal electrode 118 and the second signal electrode 119 to generate a second electrolyte solution, so that the first electrode 104, the first signal electrode 118 and the second signal electrode 119 are not easy to react with a primary cell, the probability of oxidizing the first electrode 104 is reduced, the thickness uniformity of the first electrode 104 is higher, the load vibrated by the piezoelectric laminated structure 102 is reduced, good conductivity is maintained, the reliability of the performance of the resonator is improved, and the resonator meets the requirement of a high-performance radio frequency system.

Referring to fig. 15, the resonator forming method further includes: after the second cavity 304 is formed, the first substrate 112 and the support layer 111 are etched to form a conductive via 127 exposing the second electrode 104.

Interconnect structure 128 provides for a subsequent packaging process.

In this embodiment, the first substrate 112 and the support layer 111 are etched by a dry etching process to form the conductive via 127 exposing the second electrode 106.

Referring to fig. 16, an interconnect structure 128 in contact with the first electrode 104 is formed in the conductive via 127.

In this embodiment, the material of the interconnect structure 128 includes Cu.

In this embodiment, the interconnect structure 128 is formed using a physical vapor deposition process.

Specifically, the interconnection 128 has a bottom portion corresponding to the first signal electrode 118 and the second signal electrode 119. The interconnection structure 128 is directly contacted with the second electrode 106, and in the working process of the resonator, the signal electrode and the second electrode 106 are connected in parallel, so that the contact resistance between the interconnection structure 128 and the second electrode 106 can be reduced, and the working performance of the resonator is improved. Further, in the process of forming the conductive via 127, even if the conductive via 127 is over-etched, the conductive via 127 can be etch-stopped on the first signal electrode 118 and the second signal electrode 119.

The method for forming the resonator further comprises the following steps: forming copper pillars 129 on the interconnect structures 128 of the surface of the first substrate 112 facing away from the second substrate 106; the surface of the copper pillar 129 facing away from the second electrode 106 has solder balls 210 formed thereon.

The invention also provides a resonator. Referring to fig. 16, a schematic structural diagram of a resonator of the present invention is shown.

The resonator includes: the piezoelectric laminated structure 102 comprises a working area I and a peripheral area II surrounding the working area I, wherein the piezoelectric laminated structure 102 comprises a piezoelectric layer 105, a first electrode 104 positioned on a first surface of the piezoelectric layer 105 and a second electrode 106 positioned on a second surface of the piezoelectric layer 105, and the first surface and the second surface are two opposite surfaces of the piezoelectric layer 105; a supporting layer 111 located at the peripheral region II of the second electrode 106 side and exposing the second electrode 106 of the working region I; the method comprises the steps of carrying out a first treatment on the surface of the A first substrate bonded to an end surface of the support layer 111 facing away from the piezoelectric stack structure 102, the support layer 111, the second electrode 106, and the first substrate enclosing a first cavity; a first metal bonding layer 301 penetrating the piezoelectric stack structure 102 of the peripheral region II from the first electrode 104 side and located on the support layer 111; a second substrate 122; the second metal bonding layer 303 is located on the second substrate 122, the second metal bonding layer 303 has a first opening exposing a central region of the second substrate 122, one end of the second metal bonding layer 303 away from the second substrate 122 is bonded on the first metal bonding layer 301, and the second substrate 122, the supporting layer 111, the first electrode 104, the first metal bonding layer 301 and the second metal bonding layer 303 enclose a second cavity 304.

In the resonator provided in the embodiment of the present invention, the second substrate 122, the supporting layer 111, the first electrode 104, the first metal bonding layer 301 and the second metal bonding layer 303 enclose the second cavity 304, because the metal atoms in the first metal bonding layer 301 and the second metal bonding layer 303 are tightly arranged, the ability of blocking water vapor from penetrating and isolating external water vapor is strong, even in a severe environment with high temperature and high humidity, external water vapor is not easy to pass through the first metal bonding layer 301 and the second metal bonding layer 303 and enter the second cavity, so that the first electrode 104 is not easy to react with external water vapor to generate the first electrolyte solution, the corresponding first electrode 104 is not easy to participate in the primary cell reaction, the probability of oxidizing the first electrode 104 is reduced, so that the thickness uniformity of the first electrode 104 is higher, the first electrode 104 can maintain good conductive capability, and the load caused by vibration of the piezoelectric stack structure 102 is reduced, which is beneficial to improving the reliability of the performance of the resonator, and the resonator satisfies the requirement of a high performance radio frequency system.

The piezoelectric stack 102 provides for the formation of a resonator, and the piezoelectric stack 102 is used to effect a mutual conversion between an electrical signal and an acoustic signal, thereby allowing the filter to filter the signal.

The materials, structures and positional relationships of the piezoelectric layer 105 of the first electrode 104 and the second electrode 106 are described with reference to the foregoing embodiments.

In this embodiment, the surface of the second electrode 106 is further formed with an edge bump structure 131 (Frame) surrounding the working area I, for changing the acoustic impedance of the edge, preventing the energy of the working area from leaking out, and improving the quality factor of the resonator.

In this embodiment, the supporting layer 111 has a second opening (not shown in the figure), specifically, the second opening exposes the second electrode 106 of the working area I.

The resonator further includes: the protective layer 103 is located on the end surface of the support layer 111 facing away from the piezoelectric stack structure 102, the side wall of the support layer 111, and the second electrode 106 where the support layer 111 is exposed. The protective layer 103 also covers the edge bump structure 131, and the protective layer 103 is used to protect the edge bump structure 131.

The materials, positions and structures of the relevant film layers of the protective layer and the support layer are as described with reference to the previous embodiments.

The piezoelectric stack structure 102 has a first groove (not shown) and a second groove (not shown) penetrating the first electrode 104 and the piezoelectric layer 105, and the first groove and the second groove are spaced apart.

The resonator includes: a bottom air slot (Bottom Air Trench, BAT) 125 extending through the second electrode 106 and exposing the piezoelectric layer 105, the bottom air slot 125 being proximate to the support layer 111; a Top Air Trench (TAT) 126 penetrates the first electrode 104 and exposes the piezoelectric layer 105, and the Top Air Trench 126 is close to the signal electrode.

In this embodiment, the first metal bonding layer 301 is a composite laminate layer, including: a first metal layer 205 located on an end face of the support layer 111 near the piezoelectric stack structure 102; the second metal layer 206 is located on a side of the first metal layer 301 away from the supporting layer 111. In other embodiments, the first metal bonding layer may also be a single film layer.

The materials of the first metal layer 205 include: copper, gold, aluminum, and titanium. The material of the first metal layer 205 comprises copper. Copper has good electrical and thermal conductivity and good process compatibility during semiconductor processing. The melting point of the second metal layer 206 is smaller than that of the first metal layer 205, the second metal layer 206 is used as a bonding process layer, the second metal layer 206 has the advantage of low bonding temperature, and key devices and film layers such as the piezoelectric laminated structure 102 are not easy to damage in the process of bonding the second metal layer 206. Specifically, the material of the second metal layer 206 includes tin.

In this embodiment, the thickness of the first metal bonding layer 301 is 0.5um to 0.15um. The distance L2 from the first metal bonding layer to the working area is greater than 20 nanometers. It should be noted that the second metal bonding layer is bonded to the first metal bonding layer, and the distance L2 between the corresponding second metal bonding layer and the working area is greater than 20 nm.

The resonator further includes: the first seed layer 204 is located between the support layer 111 and the first metal bonding layer 301.

In this embodiment, the material of the first seed layer 204 includes copper. The first metal layer 205 is made of the same material as the first seed layer 204, which is advantageous in that the first metal layer 205 formed by electroplating based on the first seed layer 204 has high purity and few defects.

The resonator further includes: the signal electrode penetrates through the first electrode 104 and the piezoelectric layer 105 of the inner peripheral area II of the second cavity 304 from one side of the first electrode 104, the bottom of the signal electrode is located on the second electrode 106, and the signal electrode is spaced from the first metal bonding layer 301. Specifically, the signal electrodes include a first signal electrode 118 and a second signal electrode 119 (as shown in fig. 8), and the signal electrodes are located on the second electrode 106, so that the signal electrodes are electrically connected to the second electrode 106, and the first signal electrode 118 and the second signal electrode 119 are used for inputting and outputting signals, respectively, when the resonator is in operation.

In this embodiment, the distance L1 from the bottom of the signal electrode to the working area I is greater than 10 nm.

The resonator further includes: a third seed layer 203 between the first signal electrode 118 and the first trench, between the first signal electrode 118 and the first electrode 104, between the second signal electrode 119 and the second trench, and between the second signal electrode 119 and the first electrode 104. The third seed layer 203 provides a good interface state for forming the first signal electrode 118 and the second signal electrode 119. In this embodiment, the material of the third seed layer 203 includes copper.

The resonator further includes: the first substrate 112 is bonded to the protective layer 103 of the support layer 111 facing away from the end face of the piezoelectric stack structure, and the support layer 111, the second electrode 106 and the first substrate 112 define a first cavity 123. Specifically, a covalent bond of si—o—si is formed at the contact surface of the protective layer 103 and the first substrate 112.

The first substrate 112 and second substrate materials and structures are described with reference to the previous embodiments.

In this embodiment, the second metal bonding layer 303 is composed of metal, and correspondingly, the metal atoms in the second metal bonding layer 303 are closely arranged, so that the second metal bonding layer 303 has higher compactness and has stronger permeation resistance compared with the dry film (dry film) with the mesh polymer structure as a component. Specifically, the material of the first metal layer 205 includes copper. Copper has good electrical and thermal conductivity and good process compatibility during semiconductor processing. The second metal layer 206 is used as a bonding process layer, and the second metal layer 206 has the advantage of low bonding temperature, so that the damage to key devices and film layers such as the piezoelectric stack structure 102 is not easy to occur in the bonding process using the second metal layer 206. Specifically, the material of the second metal layer 206 includes tin.

The resonator further includes: a second seed layer 306 is located between the second substrate 122 and the second metal bonding layer 303. In this embodiment, the second metal bonding layer 303 and the first metal bonding layer 301 are bonded through a metal bonding process. The metal bonding process bonds the first metal bonding layer 301 and the second metal bonding layer 303 together by metal bonding, diffusion of metal of the bonding surface, or metal melting, or the like.

The second cavity 304 is surrounded by the second substrate 122, the support layer 111, the first metal bonding layer 301 of the first electrode 104, and the second metal bonding layer 303.

The resonator further includes: a conductive via 127 penetrating the first substrate 112 and the support layer 111 to expose the second electrode 104; interconnect structures 128 are located on the bottom and sidewalls of conductive vias 127. In this embodiment, the material of the interconnect structure 128 includes Cu. The bottom of the interconnection structure 128 is in direct contact with the second electrode 106, and in the working process of the resonator, the signal electrode and the second electrode 106 are connected in parallel, so that the contact resistance between the interconnection structure 128 and the second electrode 106 can be reduced, and the working performance of the resonator is improved.

Note that, the bottom of the interconnect structure 128 corresponds to the first signal electrode 118 and the second signal electrode 119, and in the process of forming the conductive via 127, even if the conductive via 127 is over-etched, the conductive via 127 can be etched to stop on the surfaces of the first signal electrode 118 and the second signal electrode 119.

The resonator further includes: copper pillars 129 on the interconnect structure 128 on the surface of the first substrate 112 facing away from the second electrode 106; solder balls 210 are located on the surface of the copper pillars 129 facing away from the second electrode 106.

Correspondingly, the embodiment of the invention also provides a filter, which comprises the resonator of the embodiment.

The resonator of the foregoing embodiment has higher reliability, which correspondingly improves the reliability of the filter.

The resonator may be formed by the method of forming the resonator of the foregoing embodiment, or may be formed by other methods of forming resonators. In this embodiment, for a specific description of the resonator, reference may be made to the corresponding description in the foregoing embodiment, which is not repeated here.

Correspondingly, the embodiment of the invention also provides electronic equipment, which comprises the filter of the embodiment.

The filter may be assembled into various electronic devices. From the above analysis, it is clear that the reliability of the filter is high, and accordingly, a highly reliable electronic device can be obtained. The electronic device may also be a mobile terminal such as a personal computer or a smart phone, a media player, a navigation device, an electronic game device, a game controller, a tablet computer, a wearable device, an anti-access electronic system, a POS terminal, a medical device, a flight simulator, etc.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.

Claims

1. A method of forming a resonator, comprising:

providing a piezoelectric laminated structure, wherein the piezoelectric laminated structure comprises a working area and a peripheral area surrounding the working area, the piezoelectric laminated structure comprises a piezoelectric layer, a first electrode positioned on a first surface of the piezoelectric layer and a second electrode positioned on a second surface of the piezoelectric layer, and the first surface and the second surface are two opposite surfaces of the piezoelectric layer;

forming a supporting layer of the second electrode covering the peripheral region and exposing the working region from one side of the second electrode;

providing a first substrate; bonding the first substrate on the end face, away from the piezoelectric laminated structure, of the supporting layer, wherein a first cavity is formed by the supporting layer, the second electrode and the first substrate;

forming a first metal bonding layer penetrating through the piezoelectric laminated structure of the peripheral region and positioned on the supporting layer from one side of the first electrode;

Providing a second substrate;

forming a second metal bonding layer on the second substrate, the second metal bonding layer having a first opening exposing a central region of the second substrate;

and aligning the first opening to the working area, bonding the second metal bonding layer with the first metal bonding layer, and enclosing a second cavity by the second substrate, the supporting layer, the first metal bonding layer of the first electrode and the second metal bonding layer.

2. The method of forming a resonator of claim 1, wherein the method of forming a resonator comprises: etching the piezoelectric laminated structure of a part of the peripheral area before forming the first metal bonding layer after forming the supporting layer to form a peripheral groove surrounding the working area;

the step of forming a first metal bonding layer extending through the piezoelectric stack structure in the peripheral region and on the support layer includes:

forming a mask layer covering a part of the peripheral groove at the side part of the piezoelectric lamination structure inside the peripheral groove;

forming the first metal bonding layer in the peripheral groove exposed by the mask layer;

the method for forming the resonator further comprises the following steps: and removing the mask layer after the first metal bonding layer is formed.

3. The method of forming a resonator according to claim 2, wherein the step of forming the first metal bonding layer in the peripheral groove where the mask layer is exposed comprises:

forming a first metal layer on the support layer;

and forming a second metal layer on the first metal layer, wherein the first metal layer and the second metal layer serve as the first metal bonding layer.

4. The method of forming a resonator of claim 1, wherein the step of forming a second metal bonding layer on the second substrate comprises:

forming a first metal layer on the second substrate;

and forming a second metal layer on the first metal layer, wherein the first metal layer and the second metal layer serve as the second metal bonding layer.

5. The method of forming a resonator according to claim 3 or 4, wherein the first metal layer is formed using an electroplating process;

and forming the second metal layer on the first metal layer by adopting an electroplating process.

6. The method of forming a resonator of claim 3 or 4, wherein the material of the first metal layer comprises one or more of copper, gold, aluminum, and titanium; the material of the second metal layer includes tin.

7. The method of forming a resonator of claim 3 or 4, wherein the first and second metal bonding layers each have a thickness of 0.5um to 0.15um.

8. The method of forming a resonator of claim 1, wherein the first metal bonding layer and the second metal bonding layer are bonded using a metal bonding process.

9. The method of forming a resonator of claim 1, wherein the process parameters of the step of bonding the second metal bonding layer to the first metal bonding layer include: the bonding temperature is 240 ℃ to 300 ℃, the bonding pressure is 10KN to 50KN, and the environmental pressure is less than 10mTorr.

10. The method of forming a resonator of claim 2, wherein the method of forming a resonator comprises: forming a signal electrode penetrating through the first electrode and the piezoelectric layer from one side of the first electrode in the peripheral region before forming the first metal bonding layer after forming the supporting layer, wherein the signal electrode is positioned on the second electrode;

in the step of forming the first metal bonding layer, the first metal bonding layer is formed in the peripheral region of the side of the signal electrode away from the working region, and the first metal bonding layer is spaced apart from the signal electrode.

11. The method of forming a resonator of claim 10, wherein in the step of forming the signal electrode, a distance from a bottom of the signal electrode to the working area is greater than 10 nanometers.

12. The method of forming a resonator of claim 10, wherein the method of forming a resonator further comprises:

after the supporting layer is formed and before the first substrate is bonded, etching the second electrode close to a partial area of the supporting layer to form a bottom air groove penetrating the second electrode and exposing the piezoelectric layer;

after the signal electrode is formed, the first electrode is etched close to a partial area of the signal electrode, and a top air groove penetrating through the first electrode and exposing the piezoelectric layer is formed.

13. The method of forming a resonator of claim 1, wherein in the step of forming the first metal bonding layer, a distance from the first metal bonding layer to the working area is greater than 20 nanometers.

14. A resonator, comprising:

the piezoelectric lamination structure comprises a working area and a peripheral area surrounding the working area, wherein the piezoelectric lamination structure comprises a piezoelectric layer, a first electrode positioned on a first surface of the piezoelectric layer and a second electrode positioned on a second surface of the piezoelectric layer, and the first surface and the second surface are two opposite surfaces of the piezoelectric layer;

The supporting layer is positioned at the peripheral area at one side of the second electrode and exposes the second electrode of the working area;

the first substrate is bonded on the end face, away from the piezoelectric laminated structure, of the supporting layer, and the supporting layer, the second electrode and the first substrate enclose a first cavity;

a first metal bonding layer penetrating the piezoelectric stack structure of the peripheral region from one side of the first electrode and located on the support layer;

a second substrate;

the second metal bonding layer is positioned on the second substrate and provided with a first opening exposing the central area of the second substrate, one end of the second metal bonding layer, which is far away from the second substrate, is bonded on the first metal bonding layer, and a second cavity is formed by the second substrate, the supporting layer, the first electrode, the first metal bonding layer and the second metal bonding layer in a surrounding mode.

15. The resonator of claim 14, wherein the first metal bonding layer comprises:

the first metal layer is positioned on the end face, close to the piezoelectric laminated structure, of the supporting layer; the second metal layer is positioned on one side of the first metal layer away from the supporting layer;

the second metal bonding layer includes: the first metal layer is positioned on the second substrate; the said

And the second metal layer is positioned on one side of the first metal layer away from the second substrate.

16. The resonator of claim 15, wherein the material of the first metal layer comprises one or more of copper, gold, aluminum, and titanium; the material of the second metal layer includes tin.

17. The resonator of claim 14, further comprising: and the signal electrode penetrates through the first electrode and the piezoelectric layer in the inner peripheral area of the second cavity from one side of the first electrode, the bottom of the signal electrode is positioned on the second electrode, and the signal electrode is spaced from the first metal bonding layer.

18. The resonator of claim 17, wherein the resonator further comprises: a bottom air slot penetrating the second electrode and exposing the piezoelectric layer, the bottom air slot being adjacent to the support layer;

the resonator further includes: and a top air groove penetrating the first electrode and exposing the piezoelectric layer, wherein the top air groove is close to the signal electrode.

19. A filter comprising a resonator as claimed in any one of claims 14 to 18.

20. An electronic device comprising the filter of claim 19.