CN110829997B

CN110829997B - Thin film bulk acoustic resonator and method of manufacturing the same

Info

Publication number: CN110829997B
Application number: CN201810893030.8A
Authority: CN
Inventors: 王晓川
Original assignee: Xinzhiwei Shanghai Electronic Technology Co ltd
Current assignee: Xinzhiwei Shanghai Electronic Technology Co ltd
Priority date: 2018-08-07
Filing date: 2018-08-07
Publication date: 2023-04-28
Anticipated expiration: 2038-08-07
Also published as: CN110829997A

Abstract

The invention discloses a film bulk acoustic resonator and a manufacturing method thereof. The first electrode slice body and the second electrode slice body respectively comprise the first vibration buffer strip and the second vibration buffer strip in the cavity overlapping area and outside the electrode overlapping area, so that the rigidity in the horizontal direction can be effectively reduced (the flexibility is enhanced), the rigidity in the vertical direction is less influenced, and a buffer effect is achieved on horizontal elastic waves propagating along the electrode slice in the horizontal direction, so that the intensity of elastic reflected waves is reduced. In addition, the piezoelectric induction oscillation piece clamped between the first electrode piece body and the second electrode piece body is integrally arranged in the overlapping area of the cavity, and the boundary of the piezoelectric induction oscillation piece is polygonal without any parallel opposite sides, so that not only is the additional standing wave oscillation of which the horizontal direction becomes clutter eliminated, but also the energy consumed by transverse parasitic waves is reduced to the greatest extent. Corresponding manufacturing methods are also disclosed.

Description

Thin film bulk acoustic resonator and method of manufacturing the same

Technical Field

The invention relates to the technical field of filter devices, in particular to a film bulk acoustic resonator (Bulk Acoustic Wave Resonator, BAWR) and a manufacturing method thereof.

Background

With the development of mobile communication technology, the amount of mobile data transmission is rapidly increasing. Therefore, on the premise that the frequency resources are limited and as few mobile communication devices as possible should be used, the problem of increasing the transmission power of the wireless power transmission devices such as the wireless base station, the micro base station or the repeater is to be considered, and the requirement of the filter power in the front-end circuit of the mobile communication device is also increasing.

At present, a high-power filter in a wireless base station and other equipment mainly comprises a cavity filter, the power of the cavity filter can reach hundreds of watts, but the size of the filter is too large. Dielectric filters are also used in devices with average powers of up to 5 watts and the size of such filters is also large. Due to the large size, this cavity filter cannot be integrated into the radio frequency front end chip.

The thin film filter based on the semiconductor micromachining technology mainly comprises a surface acoustic wave filter (Surface Acoustic Wave Resonator, SAWR) and a Bulk Acoustic Wave Resonator (BAWR), and can well overcome the defects of the two filters. The BAWR has high working frequency, high received power, high Quality Factor (Q-Factor), small volume and easy integration.

As shown in fig. 1, a thin film bulk acoustic resonator R10 of the prior art includes a substrate R20 having a lower cavity R40, and an insulating sheet body R30 formed on the substrate R20, the lower cavity R40 being formed in the insulating sheet body R30, an oscillating device sheet body R100 formed on the substrate R20 across the lower cavity R40, the oscillating device sheet body R100 including an upper electrode R70 and a lower electrode R50, and a piezoelectric sensing sheet R60 located between the upper electrode R70 and the lower electrode R50; the oscillation device sheet body R100 is provided with a through hole R90 communicated with the lower cavity R40; the oscillator plate R50 is typically a piezoelectric film with its principal axis C-axis oriented perpendicular to the oscillator plate R100 and the upper and lower electrodes R70 and R50.

When a direct current field is applied to the upper surface and the lower surface of the piezoelectric film of the oscillating device sheet body R60 through the upper electrode R70 and the lower electrode R50, the vertical deformation of the piezoelectric film can be changed along with the size of the electric field; when the direction of the electric field is reversed, the vertical deformation (stretching or shrinking) of the piezoelectric film material is also changed. When an alternating current electric field is added, the vertical deformation of the piezoelectric film can alternately change in shrinkage or expansion along with the positive half period and the negative half period of the electric field, so that a longitudinal bulk acoustic wave propagating along the direction R1 of the C axis is formed; the longitudinal sound wave is transmitted to the interface between the upper electrode and the lower electrode and the air to be reflected back, and then is reflected back and forth in the film to form oscillation; standing wave oscillations are generated when longitudinal sound waves propagate in the piezoelectric film just an odd multiple of half the wavelength.

However, when the longitudinal acoustic wave propagates along the piezoelectric film, due to the physical poisson effect of the piezoelectric film, the deformation along the vertical direction of the thickness can generate deformation along the horizontal direction R2, so that transverse parasitic waves can be generated in the piezoelectric film, and propagate along the horizontal direction until the cavity boundary R102 of the lower cavity R30 and the oscillation device sheet body R100 meet and the boundary R101 of the piezoelectric sensing sheet R60, and propagate along the opposite direction R2 after reflection, if the transverse parasitic waves also generate additional standing wave oscillation which becomes clutter, not only energy loss is caused, but also longitudinal noise standing waves are excited similarly due to the physical poisson effect, so that the quality factor, namely the Q value, of the BAWR is greatly influenced. Meanwhile, the sound wave propagates in the piezoelectric film and the deformation thereof can cause the deformation and oscillation of the upper electrode film and the lower electrode film in the horizontal direction, and propagates outwards, reflects and even generates the induced standing wave, and possibly causes another secondary sound wave or standing wave in the sound wave piezoelectric film again, thereby further affecting the quality factor.

Therefore, how to suppress the influence of the transverse parasitic wave of the BAWR on the crosstalk of the longitudinal bulk acoustic wave signal along the C-axis direction, especially solve the problems of the transverse resonance wave and the reflection thereof in the piezoelectric film and causing the upper and lower electrodes, and at the same time, reduce the energy consumption of the acoustic wave propagating out of the oscillating device sheet to the maximum extent, and realize the connection with the external input and output electric signal source, which is the focus of attention in the industry.

Disclosure of Invention

The invention aims to provide a film bulk acoustic resonator and a manufacturing method thereof, which solve the problem that the film bulk acoustic resonator in the prior art has elastic reflected waves in the horizontal direction.

In order to solve the above technical problems, the present invention provides a thin film bulk acoustic resonator, including:

the first substrate and the second substrate which are stacked up and down respectively comprise a first cavity and a second cavity which are opposite to each other, and a cavity overlapping area which is overlapped with each other is formed;

a first electrode slice body and a second electrode slice body which are sequentially arranged between the first substrate and the second substrate, and an electrode overlapping area is formed in the cavity overlapping area;

a piezoelectric induction oscillating piece arranged between the first cavity and the second cavity and contained in the overlapping area of the electrodes;

the first vibration buffer strip and the second vibration buffer strip are conductive, and the rebound rigidity of horizontal vibration waves transmitted along the first electrode sheet body and the second electrode sheet body is reduced respectively.

Optionally, for the thin film bulk acoustic resonator, the first vibration buffer strip or the second vibration buffer strip is a ridge strip formed by a first electrode slice body or a second electrode slice body, and the ridge strip is locally and vertically raised in a vertical direction.

Alternatively, for the thin film bulk acoustic resonator, the ridge stripe locally vertically raised in the vertical direction is composed of vertically raised micro-strips cut apart individually.

Optionally, for the thin film bulk acoustic resonator, each of the vertical raised micro-strips has a width of 0.01 to 10 μm and a height of 0.1 to 10 μm, and a pitch between adjacent vertical raised micro-strips is 0.01 to 10 μm.

Optionally, for the thin film bulk acoustic resonator, the electrode overlapping region is a polygon that does not include parallel opposite sides.

Optionally, for the thin film bulk acoustic resonator, the first vibration buffer strip and the second electrode sheet body do not overlap, and the second vibration buffer strip and the first electrode sheet body do not overlap.

Optionally, for the thin film bulk acoustic resonator, the material of the piezoelectric sensing oscillation piece includes at least one of oxide, nitride and carbide.

Optionally, for the thin film bulk acoustic resonator, the material of the piezoelectric sensing oscillation piece includes at least one of a piezoelectric crystal or a piezoelectric ceramic.

Optionally, for the thin film bulk acoustic resonator, the piezoelectric crystal material includes at least one of quartz, lithium gallate, lithium germanate, titanium germanate, lithium niobate, lithium tantalate, aluminum nitride, zinc oxide, and lead zinc sphene.

Optionally, for the thin film bulk acoustic resonator, the materials of the first electrode slice and the second electrode slice include at least one of metal aluminum, copper, nickel, tungsten, titanium, molybdenum, silver, gold, platinum and alloys thereof.

The invention also provides a manufacturing method of the film bulk acoustic resonator, which comprises the following steps:

providing a first substrate, wherein a first cavity is formed on one side of the first substrate;

providing a sacrificial substrate, wherein a groove is formed on one side of the sacrificial substrate, and the groove surrounds the sacrificial substrate in a ring shape;

sequentially forming a second conductive film, a piezoelectric sensing film and a first conductive film on the sacrificial substrate, so that the first conductive film and the second conductive film form a recess facing the groove;

etching the first conductive film and the piezoelectric sensing film on one side to expose part of the second conductive film and part of the second conductive film to form a first electrode slice;

bonding the first substrate and the sacrificial substrate, wherein the first electrode sheet body faces the first cavity, and the exposed part of the second conductive film concave and the first conductive film concave face the first cavity, so that the first conductive film concave and the second conductive film concave are far away from the first cavity to form bulges;

removing the sacrificial substrate;

etching the second conductive film and the piezoelectric sensing film at the other side opposite to the one side to expose a part of the first conductive film and the bulge of the first conductive film to form a second electrode slice body and a piezoelectric sensing oscillation slice body, wherein the first electrode slice body and the second electrode slice body form an electrode overlapping area;

providing a second substrate, wherein a second cavity is formed on one side of the second substrate; and

bonding the second substrate and the first substrate, wherein the second electrode sheet body faces the second cavity; the first cavity and the second cavity form a cavity overlapping area which is overlapped with each other; the bulges of the first conductive film and the bulges of the second conductive film are arranged in the overlapping area of the cavity and outside the overlapping area of the electrodes, respectively become a first vibration buffer strip and a second vibration buffer strip of the first electrode slice body and the second electrode slice body, and respectively reduce the rebound rigidity of horizontal vibration waves transmitted along the first electrode slice body and the second electrode slice body.

Optionally, in the method for manufacturing a thin film bulk acoustic resonator, the first shock-absorbing strip or the second shock-absorbing strip is a ridge strip formed by a first electrode sheet body or a second electrode sheet body, and the ridge strip is locally and vertically raised in a vertical direction.

Optionally, for the method for manufacturing a thin film bulk acoustic resonator, after the protruding of the first conductive film, before the providing of the second substrate, the method further includes: patterning the protrusions of the first conductive film and the protrusions of the second conductive film to form vertical raised micro-bars which are separated in a cutting manner.

Alternatively, for the method of manufacturing a thin film bulk acoustic resonator, each of the vertical raised micro-bars has a width of 0.01 to 10 μm and a height of 0.1 to 10 μm, and the spacing between adjacent vertical raised micro-bars is 0.01 to 10 μm.

Optionally, for the method for manufacturing a thin film bulk acoustic resonator, the electrode overlapping region is a polygon not including parallel opposite sides.

Optionally, for the method for manufacturing a thin film bulk acoustic resonator, a second temperature compensation film sheet is further formed between the sacrificial substrate and the second conductive film, and a first temperature compensation film sheet is further formed on the first conductive film; the first temperature compensation film body is etched when the first conductive film and the piezoelectric sensing film are etched, and the second temperature compensation film body is etched when the second conductive film and the piezoelectric sensing film are etched.

Optionally, in the method for manufacturing a thin film bulk acoustic resonator, the protrusion of the first electrode sheet body and the second electrode sheet body do not overlap, and the protrusion of the second electrode sheet body and the first electrode sheet body do not overlap.

Compared with the prior art, the film bulk acoustic resonator and the manufacturing method thereof provided by the invention have the following advantages:

the first electrode slice body and the second electrode slice body respectively comprise the first vibration buffer strip and the second vibration buffer strip in the cavity overlapping area and outside the electrode overlapping area, so that the rigidity in the horizontal direction can be effectively reduced (the flexibility is enhanced), the rigidity in the vertical direction is less influenced, and a buffer effect is achieved on horizontal elastic waves transmitted along the electrode slice in the horizontal direction, so that the intensity of the elastic reflected waves is reduced.

Further, the ridge stripe locally vertically raised in the vertical direction is composed of vertically raised micro-stripes cut apart individually. The intensity of the elastic reflected wave in the horizontal direction can be further reduced on the premise of ensuring that the conductivity is not affected.

In addition, the piezoelectric induction oscillation piece clamped between the first electrode piece body and the second electrode piece body is integrally arranged in the overlapping area of the cavity, and the boundary of the piezoelectric induction oscillation piece is polygonal without any parallel opposite sides, so that not only is the additional standing wave oscillation of which the horizontal direction becomes clutter eliminated, but also the energy consumed by transverse parasitic waves is reduced to the greatest extent.

Drawings

FIG. 1 is a schematic diagram of a prior art vacuum sealed thin film bulk acoustic resonator;

FIGS. 2a and 2b are theoretical diagrams of the present invention when studying a thin film bulk acoustic resonator;

FIG. 3 is a schematic top view of a thin film bulk acoustic resonator according to an embodiment of the present invention;

FIG. 4 is a schematic cross-sectional view of a thin film bulk acoustic resonator according to an embodiment of the present invention;

FIG. 5 is a flow chart of a method of fabricating a thin film bulk acoustic resonator according to an embodiment of the present invention;

FIGS. 6-14 are schematic diagrams of structures of thin film bulk acoustic resonators according to various embodiments of the present invention at various steps in the fabrication process;

in the drawing the view of the figure,

r10-film bulk acoustic resonator;

r100 is an oscillation device sheet body;

r101-boundary;

r20-substrate;

r30-insulating sheet body;

r40-lower cavity;

r50-lower electrode;

r60-piezoelectric induction piece;

r70-upper electrode;

r90-via;

100-a first substrate;

11-electrode overlap region;

15-a cavity overlap region;

110-a sheet of a first insulating material;

115-a first cavity;

160-a dielectric layer;

201-a first conductive film;

202-a second conductive film;

2021-dent;

205-piezoelectric sensing film;

210-a second sheet of insulating material;

211-a first electrode wafer body;

2111-a first shock-absorbing strip;

2112-gap;

212-a second electrode sheet;

2121-a second shock-absorbing strip;

215-a second cavity;

221-piezoelectric induction oscillating piece;

261-first electrode cavity;

262-a second electrode cavity;

300-sacrificial substrate;

301-grooves;

310-sacrificial insulating material sheets;

53-boundary.

Detailed Description

The thin film bulk acoustic resonator of the present invention and the method of manufacturing the same will be described in more detail below in conjunction with the schematic drawings, in which preferred embodiments of the present invention are shown, it being understood that one skilled in the art may modify the invention described herein while still achieving the advantageous effects of the invention. Accordingly, the following description is to be construed as broadly known to those skilled in the art and not as limiting the invention.

The invention is more particularly described by way of example in the following paragraphs with reference to the drawings. Advantages and features of the invention will become more apparent from the following description and from the claims. It should be noted that the drawings are in a very simplified form and are all to a non-precise scale, merely for convenience and clarity in aiding in the description of embodiments of the invention.

In the following description, it will be understood that when a layer (or film), a sheet, a region, a pattern, or a structure is referred to as being "on" a substrate, a layer (or film), a sheet, a region, a pad, and/or a pattern, it can be directly on another layer or substrate, and/or intervening layers may also be present. In addition, it will be understood that when a layer is referred to as being "under" another layer, it can be directly under the other layer and/or one or more intervening layers may also be present. In addition, references to "upper" and "lower" on the respective layers may be made based on the drawings.

After long-term theoretical and experimental analysis, the inventor considers that the design of a Bulk Acoustic Wave Resonator (BAWR) device which is optimal in theory is as shown in fig. 2a and 2b, the whole oscillating device sheet body is formed by mutually bonding three film sheet bodies with the same size, namely an upper electrode R70, a lower electrode R50 and a piezoelectric induction sheet R60 positioned between the upper electrode R70 and the lower electrode R50, and the upper surface and the lower surface of the oscillating device sheet body R100 are both overhead in air and vacuum; in this way, all the electric energy applied to the piezoelectric sensing patch R60 through the upper electrode R70 and the lower electrode R50 reflects the elastic fluctuation of the upper electrode R70 and the lower electrode R50 inside the piezoelectric sensing patch R60 and disposed thereabove and thereabove to the maximum extent, so as to reduce the energy consumption of the sound wave propagating outside the oscillation device patch, especially the propagation of the lateral parasitic wave outside the oscillation device patch in the horizontal direction. Meanwhile, referring to the top view 2b, the shape of the whole oscillating device sheet body should be polygonal without any parallel opposite sides, so that standing wave oscillation possibly caused by the back and forth reflection of transverse parasitic waves at any point on the piezoelectric sensing piece R60 at the boundary can be effectively eliminated.

However, such an idealized Bulk Acoustic Wave Resonator (BAWR) device is practically impossible because the oscillating device body needs to be supported in some way on the one hand, while its upper and lower electrodes R70 and R50 need to be connected to an external input-output electrical signal source.

The main idea of the present invention is to provide a thin film bulk acoustic resonator, as shown in fig. 3 and 4, comprising:

the first substrate and the second substrate stacked up and down respectively comprise a first cavity 115 and a second cavity 215 which are opposite to each other, and a cavity overlapping region 15 which is overlapped with each other is formed;

a first electrode pad body 211 and a second electrode pad body 212 sequentially disposed between the first substrate and the second substrate, and an electrode overlapping region 11 is formed in the cavity overlapping region 15;

a piezoelectric sensing patch 221 disposed between the first cavity 115 and the second cavity 215 and contained within the electrode overlap region 11;

wherein, inside the cavity overlap region 15 and outside the electrode overlap region 11, the first electrode sheet 211 and the second electrode sheet 212 respectively comprise a first vibration buffer bar 2111 and a second vibration buffer bar 2121, and the first vibration buffer bar 2111 and the second vibration buffer bar 2121 have conductivity and respectively reduce the rebound stiffness of horizontal vibration waves propagating along the first electrode sheet 211 and the second electrode sheet 212.

By including the first vibration buffer strip 2111 and the second vibration buffer strip 2121 in the cavity overlap region 15 and outside the electrode overlap region 11, respectively, the first electrode sheet 211 and the second electrode sheet 212 can effectively reduce the rigidity in the horizontal direction (enhance flexibility) while affecting the rigidity in the vertical direction, and play a role in buffering the horizontal elastic wave propagating along the electrode sheet in the horizontal direction, thereby reducing the intensity of the elastic reflected wave.

Further, the first vibration buffer strip (2111) or the second vibration buffer strip (2121) is formed of a first electrode sheet body (211) or a second electrode sheet body (212) respectively and is a ridge strip which is locally and vertically raised in the vertical direction. The ridge stripe locally vertically raised in the vertical direction is composed of vertically raised micro-strips cut apart individually. The intensity of the elastic reflected wave in the horizontal direction can be further reduced on the premise of ensuring that the conductivity is not affected.

For example, each of the vertical raised micro-bars has a width W1 of 0.01 to 10 μm, for example, 0.02 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.5 μm, 1 μm, 3 μm, 5 μm, etc., a height H of 0.1 to 10 μm, for example, 0.5 μm, 1 μm, 3 μm, 5 μm, etc., and a pitch W2 of adjacent vertical raised micro-bars is 0.01 to 10 μm, for example, 0.02 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.5 μm, 1 μm, 3 μm, 5 μm, etc. Based on such a parameter design, the intensity of the elastic reflected wave in the horizontal direction can be reduced more effectively.

The vertical protrusion does not completely limit the side wall of the shock-absorbing strip to be perpendicular to the horizontal direction (i.e., the extending direction of the first electrode sheet 211), but only the protruding direction of the shock-absorbing strip is perpendicular to the horizontal direction (or substantially perpendicular to the horizontal direction).

In addition, the piezoelectric induction oscillating piece 221 sandwiched between the first electrode piece 211 and the second electrode piece 212 is integrally disposed in the cavity overlapping region 15, and its boundary is polygonal without any parallel opposite sides, so that not only is the additional standing wave oscillation of the clutter in the horizontal direction eliminated, but also the energy consumed by the transverse parasitic wave is reduced to the greatest extent.

In one embodiment, the material of the piezoelectric sensing oscillation piece 221 includes at least one of oxide, nitride, and carbide.

In one embodiment, the piezoelectric sensing oscillation piece 221 is made of at least one of piezoelectric crystal or piezoelectric ceramic.

In one embodiment, the piezoelectric crystal material comprises at least one of quartz, lithium gallate, lithium germanate, titanium germanate, lithium niobate, lithium tantalate, aluminum nitride, zinc oxide, and plumbite.

In one embodiment, the material of the first electrode slice 211 and the second electrode slice 212 includes at least one of aluminum, copper, nickel, tungsten, titanium, molybdenum, silver, gold, platinum, and alloys thereof.

In order to realize the thin film bulk acoustic resonator of the present invention, as shown in fig. 5, the manufacturing method includes:

step S11, providing a first substrate, wherein a first cavity is formed on one side of the first substrate;

step S12, providing a sacrificial substrate, wherein a groove is formed on one side of the sacrificial substrate, and the groove surrounds the sacrificial substrate in a ring shape;

step S13, sequentially forming a second conductive film, a piezoelectric sensing film and a first conductive film on the sacrificial substrate, so that the first conductive film and the first conductive film form a recess facing the groove;

step S14, etching the first conductive film and the piezoelectric sensing film on one side to expose part of the second conductive film and part of the second conductive film to form a first electrode slice;

step S15, bonding the first substrate and the sacrificial substrate, wherein the first electrode sheet body faces the first cavity, and the exposed part of the recess of the second conductive film and the recess of the first conductive film faces the first cavity, so that the recess of the first conductive film and the recess of the second conductive film are far away from the first cavity and become bulges;

step S16, removing the sacrificial substrate;

step S17, etching the second conductive film and the piezoelectric sensing film at the other side opposite to the one side, exposing a part of the first conductive film and the bulge of the first conductive film to form a second electrode sheet body and a piezoelectric sensing oscillation sheet, wherein the first electrode sheet body and the second electrode sheet body form an electrode overlapping area;

step S18, providing a second substrate, wherein a second cavity is formed on one side of the second substrate; and

step S19, bonding the second substrate and the first substrate, wherein the second electrode slice body faces the second cavity; the first cavity and the second cavity form a cavity overlapping area which is overlapped with each other; the bulges of the first conductive film and the bulges of the second conductive film are arranged in the overlapping area of the cavity and outside the overlapping area of the electrodes, respectively become a first vibration buffer strip and a second vibration buffer strip of the first electrode slice body and the second electrode slice body, and respectively reduce the rebound rigidity of horizontal vibration waves transmitted along the first electrode slice body and the second electrode slice body.

Specifically, referring to fig. 4, for step S11, a first substrate is provided, and a first cavity 115 is formed on one side of the first substrate. In one embodiment, the first substrate includes a first substrate 100, a first insulating material body 110 is formed on the first substrate 100, and a first cavity 115 is formed in the first insulating material body 110 at a side facing away from the first substrate 100. The selection of the first substrate 100 is well known to those skilled in the art, for example, the first substrate 100 may be a monocrystalline silicon substrate, a germanium substrate or other semiconductor material known to those skilled in the art, and the first substrate 100 may have a buried layer or the like structure or be subjected to ion implantation to form a well region or the like, as required. For another example, in one embodiment of the present invention, a semiconductor device including a CMOS active device and electrical interconnects may also be formed on the substrate 100.

In one embodiment, the material of the first insulating material body 110 includes at least one of oxide, nitride, and carbide. For example, silicon oxide, silicon nitride, silicon carbide, silicon oxynitride, and the like may be used, but the material is not limited to the above.

In one embodiment, the first insulating material body 110 may be formed using a Chemical Vapor Deposition (CVD) process, for example, using silicon oxide, and may be formed using, for example, thermal oxidation.

The first cavity 115 may be formed by wet etching and/or dry etching, and the specific shape of the first cavity 115 is not limited, and may be, for example, rectangular, or other polygonal shapes; the dimensions of the first cavity 115 are not limited, and may be set by those skilled in the art according to practical needs, such as height, side length, occupied area, etc.

Referring to fig. 7, for step S12, a sacrificial substrate is provided, one side of which is formed with a groove 301, which is annular around. In one embodiment, the sacrificial substrate includes a sacrificial substrate 300, a sheet 310 of sacrificial insulating material is formed on the sacrificial substrate 300, and a recess 301 is formed in the sheet 310 of sacrificial insulating material on a side facing away from the sacrificial substrate 300. The sacrificial substrate 300 may be a common substrate, for example, may be the same material as the first substrate 100, but the sacrificial substrate 300 may not have a structure including a CMOS active device and an electrical interconnect formed therein.

For example, the material of the sacrificial insulating material body 310 includes at least one of oxide, nitride, and carbide. Silicon oxide, silicon nitride, silicon carbide, silicon oxynitride, and the like may be used, but the material is not limited to the above.

The recess may be one or more, for example a plurality of recesses in a ring around. In this embodiment, a groove is taken as an example for illustration.

With continued reference to fig. 7, for step S13, a second conductive film 202, a piezoelectric sensing film 205 and a first conductive film 201 are sequentially formed on the sacrificial substrate, so that the first conductive film 201 and the second conductive film 202 both form a recess 2021 (as shown in fig. 9) facing the recess 301.

In one embodiment, the materials of the first conductive film 201 and the second conductive film 202 include at least one of aluminum, copper, nickel, tungsten, titanium, molybdenum, silver, gold, platinum, and alloys thereof.

In one embodiment, the piezoelectric sensing thin film 205 comprises at least one of an oxide, a nitride, and a carbide. The piezoelectric sensing film 205 is made of at least one of piezoelectric crystal or piezoelectric ceramic, such as at least one of quartz, lithium gallate, lithium germanate, titanium germanate, lithium niobate, lithium tantalate, aluminum nitride, zinc oxide and lead zinc sphene.

Then, the second conductive film 202, the piezoelectric sensing film 205 and the first conductive film 201 can be modified according to actual needs, and adjusted to the required basic pattern range, so that the portion with poor edge quality can be removed conveniently.

Next, referring to fig. 8, for step S14, the first conductive film 201 and the piezoelectric sensing film 205 are etched on one side, so as to expose a portion of the second conductive film 202 and a portion of the recess of the second conductive film 202, thereby forming a first electrode sheet 211. The exposed portion of the second conductive film 202 is provided with a first electrode cavity 261, which may be used to define a portion of the boundary of the piezoelectric sensing patch to be formed.

Specifically, the method comprises the following steps: etching is performed on one side of the first conductive film 201 to expose a portion of the piezoelectric sensing film 205, thereby forming the first electrode sheet 211. The etching removal can be performed by dry etching or etching.

In etching the first conductive film, for example, for wet etching, a photoresist may be used as a mask, and in particular, the photoresist is patterned, for example, the patterned photoresist has a plurality of non-parallel sides where the first conductive film is exposed.

After etching the first conductive film, etching the piezoelectric sensing film 205 is continued to expose the second conductive film 202. At this time, the etching of the piezoelectric sensing thin film 205 may use the photoresist or the etched first conductive thin film as a mask.

After this step, on the one hand, the preparation of the first electrode sheet 211 is completed; on the other hand, a depression of a part of the second conductive film 202 is exposed, which depression is then converted into a second shock-absorbing strip 2121 (as shown in fig. 4), and in addition, a part of the structure (including the first conductive film 201, the piezoelectric sensing film 205 and the second conductive film 202) on the side of the first electrode cavity 261 away from the recess may also serve as a boundary mechanical support, which is embodied when the second substrate is provided for bonding.

Then, referring to fig. 10 for step S15, the first substrate and the sacrificial substrate are bonded, the first electrode body 211 faces the first cavity 115, and the exposed portions of the recess of the second conductive film 202 and the recess of the first conductive film 201 face the first cavity 115, so that the recess of the first conductive film and the recess of the second conductive film are raised away from the first cavity 115.

The bonding process may be accomplished using prior art techniques and is not described in detail herein.

In one embodiment, after bonding, the vertical projection of a portion of the first electrode cavity onto the first substrate 100 falls within the vertical projection of the first cavity 115 onto the first substrate 100, while a portion may fall outside of this range. That is, for one side of the etching, the first cavity boundary of the first cavity 115 may fall on the first electrode cavity, and for the other side, where the etching is not performed, the recess of the first conductive film 201 falls completely in the boundary of the first cavity 115.

After the bonding is completed, step S16 is performed to remove the sacrificial substrate. Wherein fig. 10 may be a schematic diagram after removal of the sacrificial substrate.

The removal of the sacrificial substrate may be performed using conventional means. Such as chemical means, which may be erosion of the sacrificial insulating material sheet 310, or physical means, which may be in the form of grinding, cutting, etc.

In one embodiment, where a sheet 310 of sacrificial insulating material is present, the sacrificial insulating material sheet 310 is also removed after the sacrificial substrate is removed.

Thereafter, referring to fig. 10, for step S17, the second conductive film 202 and the piezoelectric sensing film 205 are etched at the other side opposite to the one side, and a portion of the first conductive film 201 and the protrusion of the first conductive film are exposed to form a second electrode sheet 212 and a piezoelectric sensing oscillation piece 221, and the first electrode sheet 211 and the second electrode sheet 212 form an electrode overlapping region. On the exposed portion of the first conductive film 201 is a second electrode cavity 262, which may be defined as a portion of the boundary of the piezoelectric sensing patch to be formed.

This step may be similar to the etching of step S14, and is not repeated here as the person skilled in the art is well aware of this operation.

After this step, on the one hand, the preparation of the second electrode sheet 212 is completed; on the other hand, a depression of a part of the first conductive film 201 is exposed, which depression is converted into a first vibration buffer strip 2111 (as shown in fig. 4) later, and in addition, a part of the structure (including the first conductive film 201, the piezoelectric sensing film 205 and the second conductive film 202) away from the groove on the side of the second electrode cavity 262 may also serve as a boundary mechanical support, which is embodied when the second substrate is provided for bonding.

The protrusions of the first conductive film and the protrusions of the second conductive film become the first vibration buffer bar 2111 and the second vibration buffer bar 2121 of the first electrode sheet 211 and the second electrode sheet 212, respectively, and reduce the rebound stiffness of the horizontal vibration wave propagating along the first electrode sheet 211 and the second electrode sheet 212, respectively.

In one embodiment, the first shock-absorbing strip 2111 does not overlap the second electrode plate body 212, and the second shock-absorbing strip 2121 does not overlap the first electrode plate body 211 (as shown in fig. 3).

In one embodiment, the first vibration buffer bar 2111 or the second vibration buffer bar 2121 is formed of a ridge bar that is partially and vertically raised in the vertical direction by the first electrode sheet 211 or the second electrode sheet 212, respectively.

Further, the ridge stripe locally vertically raised in the vertical direction is composed of vertically raised micro-stripes which are cut apart individually.

To achieve this structure, after step S15, it may further include: patterning the protrusions of the first conductive film and the protrusions of the second conductive film to form vertical raised micro-bars which are separated in a cutting manner.

The patterning process may be accomplished by photolithographic etching.

In one embodiment, as shown in FIG. 11, each of the vertical raised micro-bars has a width W1 of 0.01 to 10 μm, for example, 0.02 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.5 μm, 1 μm, 3 μm, 5 μm, etc., a height H of 0.1 to 10 μm, for example, 0.5 μm, 1 μm, 3 μm, 5 μm, etc., and a pitch W2 of adjacent vertical raised micro-bars is 0.01 to 10 μm, for example, 0.02 μm, 0.05 μm, 0.08 μm, 0.1 μm, 0.5 μm, 1 μm, 3 μm, 5 μm, etc.

In one embodiment, the electrode overlap region 11 is a polygon that does not include parallel opposite sides. The boundary of the piezoelectric sensing oscillation piece 221 sandwiched between the first electrode piece 211 and the second electrode piece 212 is also polygonal without any parallel opposite sides, which not only eliminates the additional standing wave oscillation of which the horizontal direction becomes clutter, but also reduces the energy consumed by the transverse parasitic wave to the greatest extent.

Then, referring to fig. 13 and 14, for step S18, a second substrate is provided, and a second cavity is formed on one side of the second substrate.

In one embodiment, the second substrate may include, for example, a second substrate (not shown) and a second sheet of insulating material 210; the second sheet of insulating material 210 may be prepared on a second substrate (not shown).

A second cavity 215 is formed in the second sheet of insulating material 210.

In one embodiment, the second cavity 215 is substantially identical to the first cavity 115.

Fig. 13 and 14 are schematic cross-sectional views along the X-X direction and the Y-Y direction in fig. 3, respectively, so as to more clearly show the technical solution of the present invention.

Thereafter, please continue to refer to fig. 13 and 14, for step S19, bonding the second substrate to the first substrate is performed, and the second electrode sheet 212 faces the second cavity 215; the first cavity 115 and the second cavity 115 form a cavity overlap region 15 that overlaps each other; the protrusions of the first conductive film and the protrusions of the second conductive film are located inside the cavity overlapping region 15 and outside the electrode overlapping region 11, respectively become a first vibration buffer bar 2111 and a second vibration buffer bar 2121 of the first electrode sheet 211 and the second electrode sheet 212, and respectively reduce the rebound stiffness of the horizontal vibration wave propagating along the first electrode sheet 211 and the second electrode sheet 212.

As shown in fig. 14, since there is no support at Y-Y, a dielectric layer 160 may be formed on the first substrate 100, thereby facilitating smooth completion of the bonding process and achieving protection of the internal oscillation sheet and the electrode sheet of the thin film bulk acoustic resonator.

In one embodiment, the method further includes forming a second temperature compensation film sheet (not shown) between the sacrificial substrate 300 and the second conductive film 202, and forming a first temperature compensation film sheet (not shown) on the first conductive film 201; this step may be completed in step S13 as shown in fig. 7.

Correspondingly, the first temperature compensation film body is etched first when the first conductive film 201 and the piezoelectric sensing film 205 are etched, and the second temperature compensation film body is etched first when the second conductive film 201 and the piezoelectric sensing film 205 are etched. In this regard, those skilled in the art will be able to know and perform correctly.

It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

1. A thin film bulk acoustic resonator comprising:

a first substrate and a second substrate stacked up and down, each including a first cavity (115) and a second cavity (215) opposite to each other, and forming a cavity overlapping region (15) overlapping each other;

a first electrode sheet body (211) and a second electrode sheet body (212) which are sequentially arranged between the first substrate and the second substrate, and an electrode overlapping area (11) is formed in the cavity overlapping area (15);

a piezoelectric sensing patch (221) disposed between the first cavity (115) and the second cavity (215) and contained within the electrode overlap region (11);

wherein, inside the cavity overlapping region (15) and outside the electrode overlapping region (11), the first electrode sheet body (211) and the second electrode sheet body (212) respectively comprise a first vibration buffer strip (2111) and a second vibration buffer strip (2121), and the first vibration buffer strip (115) and the second vibration buffer strip (125) are both conductive and respectively reduce the rebound rigidity of horizontal body vibration waves transmitted along the first electrode sheet body (211) and the second electrode sheet body (212).

2. The thin film bulk acoustic resonator according to claim 1, wherein the first shock-absorbing strip (2111) or the second shock-absorbing strip (2121) is a ridge strip formed by a first electrode sheet (211) or a second electrode sheet (212), respectively, which is locally and vertically raised in the vertical direction.

3. The thin film bulk acoustic resonator of claim 2, wherein the ridge stripe locally vertically raised in the vertical direction is composed of vertically raised micro-strips individually cut apart.

4. The thin film bulk acoustic resonator of claim 1, wherein each of the vertical ridge micro-strips has a width of 0.01 to 10 μm and a height of 0.1 to 10 μm, and a pitch between adjacent vertical ridge micro-strips is 0.01 to 10 μm.

5. The thin film bulk acoustic resonator of claim 1, wherein the electrode overlap region (11) is a polygon that does not include mutually parallel opposite sides.

6. The thin film bulk acoustic resonator of claim 1, wherein the first shock-absorbing strip does not overlap the second electrode sheet, and the second shock-absorbing strip does not overlap the first electrode sheet.

7. The thin film bulk acoustic resonator according to claim 1, characterized in that the material of the piezoelectric sensing patch (221) comprises at least one of an oxide, a nitride, a carbide.

8. The thin film bulk acoustic resonator of claim 1, wherein the material of the piezoelectric sensing patch (221) comprises at least one of a piezoelectric crystal or a piezoelectric ceramic.

9. The thin film bulk acoustic resonator of claim 8, wherein the piezoelectric crystal material comprises at least one of quartz, lithium gallate, lithium germanate, titanium germanate, lithium niobate, lithium tantalate, aluminum nitride, zinc oxide, and lead zinc sphene.

10. The thin film bulk acoustic resonator of claim 1, wherein the material of the first electrode plate (211) and the second electrode plate (212) comprises at least one of metallic aluminum, copper, nickel, tungsten, titanium, molybdenum, silver, gold, platinum, and alloys thereof.

11. A method of manufacturing a thin film bulk acoustic resonator, comprising:

providing a first substrate, one side of which forms a first cavity (115);

sequentially forming a second conductive film (202), a piezoelectric sensing film (205) and a first conductive film (201) on the sacrificial substrate, so that the first conductive film and the second conductive film both form a recess facing the groove;

etching the first conductive film (201) and the piezoelectric sensing film (205) on one side to expose part of the second conductive film and part of the second conductive film to form a first electrode slice (211);

bonding the first substrate and the sacrificial substrate, wherein the first electrode sheet body (211) faces the first cavity, and the exposed part of the recess of the second conductive film and the recess of the first conductive film faces the first cavity, so that the recess of the first conductive film and the recess of the second conductive film are far away from the first cavity and become bulges;

removing the sacrificial substrate;

etching the second conductive film (201) and the piezoelectric sensing film (205) at the other side opposite to the one side, exposing a part of the first conductive film and the bulge of the first conductive film to form a second electrode sheet body (212) and a piezoelectric sensing oscillation piece (221), wherein the first electrode sheet body and the second electrode sheet body form an electrode overlapping area (11);

providing a second substrate, one side of which forms a second cavity (215); and

bonding the second substrate to the first substrate, the second electrode sheet (212) facing the second cavity; -the first cavity (115) and the second cavity (215) form a cavity overlap region (15) overlapping each other; the protrusions of the first conductive film and the protrusions of the second conductive film are arranged in the cavity overlapping area (15) and outside the electrode overlapping area (11) and respectively become a first vibration buffer strip (2111) and a second vibration buffer strip (2121) of the first electrode slice body (211) and the second electrode slice body (212), and rebound rigidity of horizontal vibration waves transmitted along the first electrode slice body (211) and the second electrode slice body (212) is reduced.

12. The method of manufacturing a thin film bulk acoustic resonator according to claim 11, wherein the first shock-absorbing strip (2111) or the second shock-absorbing strip (2121) is a ridge strip formed of a first electrode sheet (211) or a second electrode sheet (212), respectively, which is locally and vertically raised in a vertical direction.

13. The method of manufacturing a thin film bulk acoustic resonator according to claim 12, characterized in that after the protruding of the first conductive film, before providing the second substrate, further comprising: patterning the protrusions of the first conductive film and the protrusions of the second conductive film to form vertical raised micro-bars which are separated in a cutting manner.

14. The method of manufacturing a thin film bulk acoustic resonator according to claim 13, wherein each of the vertical ridge micro-strips has a width of 0.01 to 10 μm and a height of 0.1 to 10 μm, and a pitch between adjacent vertical ridge micro-strips is 0.01 to 10 μm.

15. The method of manufacturing a thin film bulk acoustic resonator according to claim 11, characterized in that the electrode overlap region (11) is a polygon which does not comprise mutually parallel opposite sides.

16. The method of manufacturing a thin film bulk acoustic resonator according to claim 11, characterized in that a second temperature compensation film sheet is further formed between the sacrificial substrate and the second conductive film (202), and a first temperature compensation film sheet is further formed on the first conductive film (201); the first temperature compensation film body is etched first when the first conductive film (201) and the piezoelectric sensing film (205) are etched, and the second temperature compensation film body is etched first when the second conductive film (201) and the piezoelectric sensing film (205) are etched.

17. The method of manufacturing a thin film bulk acoustic resonator according to claim 11, wherein the protrusion of the first electrode tab does not overlap the second electrode tab, and wherein the protrusion of the second electrode tab does not overlap the first electrode tab.