CN109167585A - Bulk acoustic wave resonator and preparation method thereof, filter - Google Patents

Bulk acoustic wave resonator and preparation method thereof, filter Download PDF

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Publication number
CN109167585A
CN109167585A CN201810838308.1A CN201810838308A CN109167585A CN 109167585 A CN109167585 A CN 109167585A CN 201810838308 A CN201810838308 A CN 201810838308A CN 109167585 A CN109167585 A CN 109167585A
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Prior art keywords
acoustic wave
wave resonator
bulk acoustic
reflection unit
pad
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CN201810838308.1A
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CN109167585B (en
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李平
王伟
胡念楚
贾斌
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Kaiyuan Communication Technology (xiamen) Co Ltd
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Kaiyuan Communication Technology (xiamen) Co Ltd
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02015—Characteristics of piezoelectric layers, e.g. cutting angles
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02086—Means for compensation or elimination of undesirable effects
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/02—Details
    • H03H9/02535—Details of surface acoustic wave devices
    • H03H9/02818—Means for compensation or elimination of undesirable effects
    • H03H9/02842—Means for compensation or elimination of undesirable effects of reflections
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
    • H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
    • H03H9/171—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
    • H03H9/172—Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume
    • H03H9/174—Membranes
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material

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

Abstract

The present disclosure proposes a kind of bulk acoustic wave resonators and preparation method thereof, filter, wherein the bulk acoustic wave resonator includes: a substrate；A sound reflecting unit over the substrate；A piezo-electric stack structure on the sound reflecting unit；And the pad in the piezo-electric stack structure；Wherein, the pad and the sound reflecting unit have an overlapping region.Disclosure bulk acoustic wave resonator and preparation method thereof, filter, effectively reduce the connection resistance of bulk acoustic wave resonator, and then can reduce the insertion loss of filter.

Description

Bulk acoustic wave resonator, manufacturing method thereof and filter
Technical Field
The disclosure relates to the technical field of radio frequency chips, in particular to a bulk acoustic wave resonator, a manufacturing method thereof and a filter.
Background
Surface Acoustic Wave (SAW) and Film Bulk Acoustic Wave (BAW) filters are two important technologies used in current radio frequency filters of smart phones.
With the popularization of 4G (the 4th Generation mobile communication technology)/lte (long term evolution) multiband smart phones and the commissioning of 5G (the 5th Generation mobile communication technology), mobile communication frequencies are higher and higher, bandwidths are wider and higher, and performance requirements on radio frequency filters are higher and higher.
The bulk acoustic wave filter has lower insertion loss, better roll-off characteristic, lower temperature coefficient and larger power bearing capacity, and is widely applied to 4G communication. However, with the commissioning of 5G, the data transmission speed of mobile communication is faster and the spectrum resource is more and more crowded. This requires, on the one hand, a wider bandwidth of the filter and, on the other hand, a better roll-off behavior, lower insertion loss of the filter. The working frequency of the bulk acoustic wave filter is inversely proportional to the thickness of the film, so that at high frequency, the electrode of the bulk acoustic wave filter becomes thinner and thinner, and the thinning of the electrode causes the connection resistance to become larger, thereby affecting the insertion loss of the bulk acoustic wave filter, and therefore, the reduction of the connection resistance of the bulk acoustic wave filter has important significance.
The bulk acoustic wave resonator is a basic unit constituting a bulk acoustic wave filter, and its basic structure includes a piezoelectric film, a bottom electrode and a top electrode sandwiched on both sides of the piezoelectric film, and an acoustic reflection unit located below the bottom electrode. The overlapping area between the acoustic reflection unit, the bottom electrode, the top electrode, and the piezoelectric film forms an active region in which the bulk acoustic wave resonator operates. When a radio frequency signal is applied between the electrodes, the piezoelectric film vibrates due to the inverse piezoelectric effect, generating an acoustic wave that propagates in a direction perpendicular to the electrode surfaces and is reflected at the upper and lower interfaces. When the frequency of the applied radio frequency signal is the same as the resonator frequency of the piezoelectric film, the radio frequency signal can pass through, thereby achieving the filtering effect.
Chinese patent No. CN103166596A discloses a resonator and a filter, wherein the thin film piezoelectric resonator includes: the substrate E, the acoustic reflection structure D, the lower electrode B, the piezoelectric layer P, the upper electrode T and the connection structure C. The overlapping portion of the upper electrode T, the piezoelectric layer P, the lower electrode B, and the acoustic reflection structure D is defined as an effective area a of the thin film piezoelectric resonator. The upper electrode T includes a portion T1 in an effective area and a lead-out portion T2, as shown in fig. 1. The connection structure C added to the resonator is positioned outside the effective working area of the resonator (d is greater than or equal to 0.1um), and the resistance of the signal passing electrode end is not reduced, so that the connection resistance of the resonator cannot be effectively reduced.
US20170346462a1 discloses a method of manufacturing a bulk acoustic wave resonator, said bulk acoustic wave resonator 70 comprising a substrate 71, a bottom electrode 72, a bottom electrode thickness increasing layer 73, an additional metal part 74, a layer 75 of PZ material, a first top electrode 76, a second top electrode 77, as shown in fig. 2. The manufacturing method of the bulk acoustic wave resonator can avoid the problem that the bottom electrode is etched too thin to influence electric connection when the piezoelectric film contact hole is etched, but extra metal added by the method is distributed outside the effective area of the resonator, so that the resistance of the bottom electrode between the extra metal and the effective area cannot be reduced, and because the bottom electrode and the top electrode of the bulk acoustic wave resonator have close thicknesses in the design of a general bulk acoustic wave filter, the top electrode still has larger resistance.
In summary, the existing bulk acoustic wave resonators have the following technical defects: although the connection resistance is reduced to a certain extent, the connection resistance is still large, and the insertion loss and other performances of the final bulk acoustic wave filter are affected.
Disclosure of Invention
Technical problem to be solved
The present disclosure provides a bulk acoustic wave resonator, a method for manufacturing the same, and a filter, so as to at least partially solve the technical problems presented above.
(II) technical scheme
According to an aspect of the present disclosure, there is provided a bulk acoustic wave resonator including:
a substrate;
an acoustic reflection unit on the substrate;
a piezoelectric stack on the acoustic reflection unit; and
a pad on the piezoelectric stack; wherein,
the pad and the acoustic reflection unit have an overlapping area.
In some embodiments, the piezoelectric stack structure comprises:
a bottom electrode;
a piezoelectric film on the bottom electrode; and
a top electrode on the piezoelectric film.
In some embodiments, the piezoelectric stack further comprises a conductive film above or below the bottom electrode, the conductive film having an overlapping region with the acoustic reflection unit.
In some embodiments, the top electrode and the conductive film have an overlapping area with a width d 5; the width of the overlapping area of the conductive film and the sound reflection unit is d 3; the distance between the non-leading-out end of the top electrode and the sound reflection unit is d 4; d3 ═ d4+ d5, d4 ≥ 0, and d5 ═ k1λ/4, where λ is the equivalent wavelength of the bulk acoustic wave resonator, k1Is an odd number.
In some embodiments, at the top electrode lead-out terminal, the pad is in contact with a top electrode, and a width of an overlapping region of the pad and the acoustic reflection unit is d6, where d6 ═ k2λ/4, where λ is the equivalent wavelength of the bulk acoustic wave resonator, k2Is odd, and k1≥k2；
A contact hole is formed above the conductive thin film and on the piezoelectric film, and the bulk acoustic wave resonator further includes another pad formed at the contact hole and contacting the conductive thin film or the bottom electrode.
According to another aspect of the present disclosure, there is provided a filter comprising a plurality of the bulk acoustic wave resonators in cascade.
According to another aspect of the present disclosure, there is provided a method of manufacturing a bulk acoustic wave resonator, including:
forming an acoustic reflection unit on a substrate;
forming a piezoelectric stack structure on the acoustic reflection unit; and
manufacturing a bonding pad on the piezoelectric stack structure; wherein,
the pad and the acoustic reflection unit have an overlapping area.
In some embodiments, the step of forming a piezoelectric stack on the acoustic reflection unit includes:
forming a bottom electrode on the acoustic reflection unit;
forming a piezoelectric film on the bottom electrode; and
a top electrode is formed on the piezoelectric film.
In some embodiments, before or after the step of forming the bottom electrode, further comprising: forming a conductive film; the conductive film and the acoustic reflection unit have an overlapping region.
In some embodiments, the top electrode and the conductive film have an overlapping area with a width d 5; the width of the overlapping area of the conductive film and the sound reflection unit is d 3; the distance between the non-leading-out end of the top electrode and the sound reflection unit is d 4; d3 ═ d4+ d5, d4 ≥ 0, and d5 ═ k1λ/4, where λ is the equivalent wavelength of the bulk acoustic wave resonator, k1Is odd;
the width of the overlapping region of the pad and the sound reflection unit is d6, d6 ═ k2λ/4, where λ is the equivalent wavelength of the bulk acoustic wave resonator, k2Is odd, and k1≥k2。
(III) advantageous effects
According to the technical scheme, the bulk acoustic wave resonator, the manufacturing method thereof and the filter have at least one of the following beneficial effects:
(1) according to the bulk acoustic wave resonator, the conductive film is introduced, the pad and the acoustic reflection unit are provided with the overlapped area, the pad is extended into the effective area of the bulk acoustic wave resonator, the electrode thickness of a circuit for connecting the bottom electrode and the top electrode of the bulk acoustic wave resonator is increased, the connection resistance of the bulk acoustic wave resonator is effectively reduced, and then the insertion loss of a filter and a duplexer formed by cascading the resonator can be reduced.
(2) According to the method, the width of each overlapping area and the distance between the top electrode non-leading-out end and the acoustic reflection unit are set, and the acoustic impedance discontinuous area is formed at the edge of the bulk acoustic wave resonator effective area, so that reflection can be formed on the acoustic wave energy leaked from the edge, and the quality factor of the bulk acoustic wave resonator is improved.
Drawings
Fig. 1 is a schematic structural diagram of a bulk acoustic wave resonator in the prior art.
Fig. 2 is another schematic diagram of a prior art bulk acoustic wave resonator.
Fig. 3 is a top view of a bulk acoustic wave resonator according to an embodiment of the present disclosure.
Fig. 4 is a cross-sectional view taken along line 1A-1A of fig. 3.
Fig. 5A to 5H are flow charts illustrating a manufacturing process of a bulk acoustic wave resonator according to an embodiment of the disclosure.
Fig. 6 is a cross-sectional view of a bulk acoustic wave resonator according to another embodiment of the present disclosure.
Fig. 7A to 7H are flow charts illustrating the fabrication of a bulk acoustic wave resonator according to another embodiment of the disclosure.
Fig. 8 is a schematic diagram of the filter structure according to the present disclosure.
Detailed Description
For the purpose of promoting a better understanding of the objects, aspects and advantages of the present disclosure, reference is made to the following detailed description taken in conjunction with the accompanying drawings.
The present disclosure provides a bulk acoustic wave resonator, comprising:
a substrate;
an acoustic reflection unit on the substrate;
a piezoelectric stack on the acoustic reflection unit; and
a pad on the piezoelectric stack; wherein,
the pad and the acoustic reflection unit have an overlapping area.
In one embodiment, please refer to fig. 3 and 4, the bulk acoustic wave resonator includes:
a substrate 201;
an acoustic reflection unit 202 formed on the substrate; wherein, a Bragg reflection layer can be directly formed on the front surface of the substrate by alternately stacking materials with different acoustic impedances to form the acoustic reflection unit; the substrate may also be etched to form a groove on the substrate, the groove is filled with a sacrificial material, and then Chemical Mechanical Polishing (CMP) is performed to make the surface of the sacrificial material flush with the surface of the substrate, thereby forming the acoustic reflection unit; the latter embodiment is the present example;
an isolation layer/support layer 203 formed on the acoustic reflection unit; the isolation layer can completely cover the substrate and the front surface of the sound reflection unit, or only partially cover the front surface of the substrate, namely the isolation layer can be selectively etched together when the bottom electrode is etched, and can also be selectively not etched.
A bottom electrode 204 formed on the isolation layer; wherein the bottom electrode partially covers the front surface of the isolation layer, or completely covers the front surface of the isolation layer;
a conductive film 209 formed on the bottom electrode; wherein the conductive film partially covers the front surface of the bottom electrode;
a piezoelectric film 205 formed on the conductive thin film; etching the piezoelectric film to form a contact hole 207 on the piezoelectric film, wherein the contact hole is formed above the conductive film;
a top electrode 206 formed on the piezoelectric film, the top electrode 206 partially covering the piezoelectric film; and
a pad 208a on the top electrode and another pad 208b at the contact hole 207.
As further shown in fig. 4, the bottom electrode 204 may partially or completely cover the acoustic reflection unit 202, and the piezoelectric film 205 covers the entire bottom electrode 204 except for the contact hole 207. The pads 208a and 208b are in contact with the top electrode 206 and the conductive film 209, respectively. The conductive film 209 covers the bottom electrode 204 except for a terminal (contact edge) of the top electrode 206 (a terminal in contact with the pad 208 a) and an illustrated M region, and has an overlapping region with a non-terminal (non-contact edge) of the top electrode (a terminal not in contact with the pad 208 a).
The width of the overlapping area of the conductive film 209 and the acoustic reflection unit 202 is d3, the distance from the non-leading end of the top electrode 206 to the acoustic reflection unit 202 (the end of the acoustic reflection unit 202 far away from the pad 208 a) is d4, and the width of the overlapping area of the conductive film 209 and the top electrode 206 is d5, wherein d3 is d4+ d5, d4 is not less than 0, and d5 is k1λ/4, λ is the equivalent wavelength of the bulk acoustic wave resonator, k1Is an odd number. At the top electrode lead-out end, the land 208a is in contact with the top electrode 206 and extends to overlap with the acoustic reflection unit 202 by an overlap region width d6, d6 ═ k2λ/4, where λ is the equivalent wavelength of the bulk acoustic wave resonator, k2Is odd, and k1≥k2. Therefore, the electrode thickness of the bottom electrode and the top electrode connecting circuit is increased on one hand while the area of the effective working area is not influenced, and the connecting resistance of the bulk acoustic wave resonator is effectively reduced; on the other hand, an acoustic impedance discontinuous area is formed at the edge of the effective area of the bulk acoustic wave resonator, and better reflection can be formed on the acoustic wave energy leaked from the edge, so that the quality factor of the bulk acoustic wave resonator is improved.
The material of the conductive film 209 may be the same as the electrodes 204, 206 of the bulk acoustic wave resonator, such as molybdenum (Mo), tungsten (W), ruthenium (Ru), iridium (Ir), or the like; the electricity may be different, such as using gold (Au), platinum (Pt), copper (Cu), aluminum (Al), Graphene (Graphene), Carbon Nanotubes (CNT), etc., which have a smaller resistivity.
In this embodiment, a method for manufacturing the bulk acoustic wave resonator of this embodiment is further provided, as shown in fig. 5A to 5H, the method for manufacturing the bulk acoustic wave resonator includes:
s1, the acoustic reflection unit 202 is produced. Specifically, an acoustic reflection unit 202 is formed on the substrate; the front surface of the substrate can be directly and alternately stacked by using materials with different acoustic impedances to manufacture a Bragg reflection layer so as to form an acoustic reflection unit; or etching the substrate to form a groove on the substrate, filling the groove with a sacrificial material, and performing Chemical Mechanical Polishing (CMP) to make the surface of the sacrificial material flush with the surface of the substrate to form an acoustic reflection unit; the latter embodiment is the present example; as shown in fig. 5A.
S2, the isolation layer 203 and the bottom electrode 204 are deposited. Specifically, an isolation layer 203 is formed on the acoustic reflection unit, and a bottom electrode 204 is formed on the isolation layer, as shown in fig. 5B.
S3, the conductive film 209 is deposited and patterned. Preferably, a stripping process is used: the pattern 209 is formed by photolithography (without photoresist coverage at the position 209), a conductive film is deposited, and the photoresist and the conductive film on the photoresist are removed to form the conductive film 209, as shown in fig. 5C.
S4, the bottom electrode 204 is patterned, as shown in FIG. 5D.
S5, the piezoelectric film 205 is deposited. Specifically, a piezoelectric film 205 is formed on the conductive thin film, as shown in fig. 5E.
S6, the top electrode 206 is deposited and patterned as shown in fig. 5F.
S7, the piezoelectric film is etched to open the contact hole 207, as shown in fig. 5G.
S8, pads 208a and 208b are fabricated. Pad 208a is on the top electrode and pad 208b is at the contact hole, as shown in fig. 5H.
In another specific embodiment, the bulk acoustic wave resonator is configured as shown in fig. 6, an acoustic reflection unit 302 is provided on a substrate 301, an isolation layer/support layer 303 is provided on the acoustic reflection unit 302, a bottom electrode 304 is provided on the isolation layer/support layer 303, the bottom electrode 304 partially or completely covers the acoustic reflection unit 302, a piezoelectric film 305 is provided on the bottom electrode 304, the piezoelectric film 305 covers the entire bottom electrode 304 except for a contact hole 307, a top electrode 306 partially covers the piezoelectric film 305, and pads 308a and 308b are respectively in contact with the top electrode 306 and the bottom electrode 304. The bulk acoustic wave resonator further includes a conductive film 309 underlying the bottom electrode 304, the conductive film 309 underlying the bottom electrode 304 except for a top electrode 306 lead (an end in contact with a pad 308 a) and an illustrated M region.
The overlapping width of the conductive films 309 and 302 is d3 ', the distance from the non-leading end of the top electrode 306 to the acoustic reflection unit 302 is d 4', and the overlapping width of the conductive film 309 and the top electrode 306 is d5 ', wherein d3 ═ d 4' + d5 ', d 4' ≧ 0, and d5 ═ k1λ/4, λ is the equivalent wavelength of the bulk acoustic wave resonator, k1Is an odd number.
At the top electrode lead-out terminal, the pad 308a is in contact with the top electrode 306 and extends to overlap with the acoustic reflection unit 302 by a width d 6', d6 ═ k2λ/4, where λ is the equivalent wavelength of the bulk acoustic wave resonator, k2Is odd, and k1≥k2。
The material of the conductive film 309 may be the same as the electrodes 304, 306 of the bulk acoustic wave resonator, such as molybdenum (Mo), tungsten (W), ruthenium (Ru), iridium (Ir), or the like; it may be different, such as gold (Au), platinum (Pt), copper (Cu), aluminum (Al), Graphene (Graphene), Carbon Nanotube (CNT), etc., which have a smaller resistivity.
In this embodiment, a method for manufacturing the bulk acoustic wave resonator of this embodiment is further provided, as shown in fig. 7A to 7H, the method for manufacturing the bulk acoustic wave resonator includes:
s1, the acoustic reflection unit 302 is produced as shown in fig. 7A.
S2, an isolation layer 303 and a conductive film 309 are deposited, as shown in fig. 7B.
S3, patterning the conductive film 309, as shown in fig. 7C, specifically, an etching process may be used, or a stripping process may be used.
S4, the bottom electrode 304 is deposited and patterned, as shown in fig. 7D.
S5, the piezoelectric film 305 is deposited, as shown in fig. 7E.
S6, the top electrode 306 is deposited and patterned as shown in FIG. 7F.
S7, the piezoelectric film is etched to open the contact hole 307, as shown in fig. 7G.
S8, pads 308a and 308b are formed, as shown in fig. 7H.
In contrast, unlike the previous embodiment, the conductive film of the present embodiment is under the bottom electrode, while the conductive film of the previous embodiment is on the bottom electrode, the rest of the embodiments are the same as the previous embodiments.
As shown in fig. 8, the present disclosure also provides a filter including a plurality of the aforementioned bulk acoustic wave resonators 2 in cascade.
Furthermore, the above definitions of the various elements and methods are not limited to the particular structures, shapes or arrangements of parts mentioned in the examples, which may be easily modified or substituted by one of ordinary skill in the art, for example:
(1) the bulk acoustic wave resonator may not include an isolation layer.
(2) The bulk acoustic wave resonator may further include a passivation layer covering all areas of the top electrode not contacted by the pad and all areas of the bottom electrode not covered by the pad and the piezoelectric film.
(3) The shape of the active area of the bulk acoustic wave resonator can be square, rectangular, irregular polygon, circular or oval.
So far, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. From the above description, those skilled in the art should clearly recognize the present disclosure.
It is to be noted that, in the attached drawings or in the description, the implementation modes not shown or described are all the modes known by the ordinary skilled person in the field of technology, and are not described in detail. Further, the above definitions of the various elements and methods are not limited to the various specific structures, shapes or arrangements of parts mentioned in the examples, which may be easily modified or substituted by those of ordinary skill in the art.
Of course, the method of the present disclosure may also include other steps according to actual needs, which are not described herein again since they are not related to the innovations of the present disclosure.
The above-mentioned embodiments are intended to illustrate the objects, aspects and advantages of the present disclosure in further detail, and it should be understood that the above-mentioned embodiments are only illustrative of the present disclosure and are not intended to limit the present disclosure, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present disclosure should be included in the scope of the present disclosure.

Claims (10)

1. A bulk acoustic wave resonator comprising:
a substrate;
an acoustic reflection unit on the substrate;
a piezoelectric stack on the acoustic reflection unit; and
a pad on the piezoelectric stack; wherein,
the pad and the acoustic reflection unit have an overlapping area.
2. The bulk acoustic wave resonator according to claim 1, wherein the piezoelectric stack comprises:
a bottom electrode;
a piezoelectric film on the bottom electrode; and
a top electrode on the piezoelectric film.
3. The bulk acoustic wave resonator according to claim 2, wherein the piezoelectric stack further comprises a conductive film having an overlapping region with the acoustic reflection unit above the bottom electrode or below the bottom electrode.
4. The bulk acoustic wave resonator according to claim 3, wherein the top electrode and the conductive thin film have an overlapping area with a width d 5; the width of the overlapping area of the conductive film and the sound reflection unit is d 3; the distance between the non-leading-out end of the top electrode and the sound reflection unit is d 4; d3 ═ d4+ d5, d4 ≥ 0, and d5 ═ k1λ/4, where λ is the equivalent wavelength of the bulk acoustic wave resonator, k1Is an odd number.
5. The bulk acoustic wave resonator according to claim 4,
at the top electrode lead-out terminal, the pad is in contact with a top electrode, and a width of an overlapping region of the pad and the acoustic reflection unit is d6, where d6 k2λ/4, where λ is the equivalent wavelength of the bulk acoustic wave resonator, k2Is odd, and k1≥k2；
A contact hole is formed above the conductive thin film and on the piezoelectric film, and the bulk acoustic wave resonator further includes another pad formed at the contact hole and contacting the conductive thin film or the bottom electrode.
6. A filter comprising a plurality of bulk acoustic wave resonators as claimed in any one of claims 1 to 5 in cascade.
7. A method for manufacturing a bulk acoustic wave resonator comprises the following steps:
forming an acoustic reflection unit on a substrate;
forming a piezoelectric stack structure on the acoustic reflection unit; and
manufacturing a bonding pad on the piezoelectric stack structure; wherein,
the pad and the acoustic reflection unit have an overlapping area.
8. The method of fabricating a bulk acoustic wave resonator according to claim 7, wherein the step of forming a piezoelectric stack structure on the acoustic reflection unit comprises:
forming a bottom electrode on the acoustic reflection unit;
forming a piezoelectric film on the bottom electrode; and
a top electrode is formed on the piezoelectric film.
9. The method of fabricating a bulk acoustic wave resonator as claimed in claim 8, further comprising, before or after the step of forming the bottom electrode: forming a conductive film; the conductive film and the acoustic reflection unit have an overlapping region.
10. The method of fabricating a bulk acoustic wave resonator as claimed in claim 9, wherein the top electrode and the conductive film have an overlapping area with a width d 5; the width of the overlapping area of the conductive film and the sound reflection unit is d 3; the distance between the non-leading-out end of the top electrode and the sound reflection unit is d 4; d3 ═ d4+ d5, d4 ≥ 0, and d5 ═ k1λ/4, where λ is the equivalent wavelength of the bulk acoustic wave resonator, k1Is odd;
the width of the overlapping region of the pad and the sound reflection unit is d6, d6 ═ k2λ/4, where λ is the equivalent wavelength of the bulk acoustic wave resonator, k2Is odd, and k1≥k2。
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CN111010124A (en) * 2019-10-26 2020-04-14 诺思(天津)微系统有限责任公司 Bulk acoustic wave resonator having electrode with void layer, filter, and electronic device
CN111010119A (en) * 2019-08-15 2020-04-14 天津大学 Resonator with composite annular structure, filter and electronic equipment
CN111082775A (en) * 2019-12-30 2020-04-28 中国电子科技集团公司第五十五研究所 Film bulk acoustic resonator with high quality factor
WO2021077715A1 (en) * 2019-10-23 2021-04-29 诺思(天津)微系统有限责任公司 Bulk acoustic wave resonator provided with electrodes having gap layer and protruding structure, filter and electronic device

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