CN109687835B - Film bulk acoustic resonator, manufacturing method thereof and filter - Google Patents

Film bulk acoustic resonator, manufacturing method thereof and filter Download PDF

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Publication number
CN109687835B
CN109687835B CN201811551626.6A CN201811551626A CN109687835B CN 109687835 B CN109687835 B CN 109687835B CN 201811551626 A CN201811551626 A CN 201811551626A CN 109687835 B CN109687835 B CN 109687835B
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lower electrode
layer
substrate
piezoelectric
electrode layer
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CN109687835A (en
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彭波华
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
    • H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
    • H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
    • H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
    • 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
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02086—Means for compensation or elimination of undesirable effects
    • H03H9/02102—Means for compensation or elimination of undesirable effects of temperature influence
    • 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
    • H03H9/0211—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
    • H03H9/02—Details
    • H03H9/02007—Details of bulk acoustic wave devices
    • H03H9/02086—Means for compensation or elimination of undesirable effects
    • H03H9/02133—Means for compensation or elimination of undesirable effects of stress
    • 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
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezo-electric or electrostrictive material
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
    • H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
    • H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
    • H03H2003/023—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks the resonators or networks being of the membrane type

Abstract

The disclosure provides a film bulk acoustic resonator, a manufacturing method thereof and a filter; wherein the film bulk acoustic resonator includes: the piezoelectric device comprises a substrate and a piezoelectric stack structure, wherein the piezoelectric stack structure is formed on the substrate; wherein a center pillar structure is formed at an eccentric position of the film bulk acoustic resonator, and a cavity is formed around the center pillar structure. The method and the device reduce the influence of external stress on the resonant frequency of the device, and are suitable for application with higher frequency stability requirements.

Description

Film bulk acoustic resonator, manufacturing method thereof and filter
Technical Field
The disclosure belongs to the technical field of wireless communication, and particularly relates to a film bulk acoustic resonator, a manufacturing method thereof and a filter.
Background
Film Bulk Acoustic Resonators (FBARs) rely on the advantages of high Q-factor, large coupling coefficient, etc. and are used in present-day rf filters and oscillators.
One of the major problems faced by oscillators is that external stresses are transmitted to the resonator, which causes a change in the resonant frequency, which in turn affects the center frequency of the oscillator. Such as oscillators made from FBARs, are typically mounted on a Printed Circuit Board (PCB) that contains metal and a laminate medium. When the PCB is heated or cooled, the PCB board can deform, and the generated stress is transferred to the FBAR, so that the resonant frequency is changed. Although the frequency of the change is small, the frequency deviation is more serious than that caused by aging and the like, and the dequantization is difficult.
For the application in the high-precision electronic field, the frequency deviation caused by external force is difficult to meet the requirements of devices. For example, the frequency offset of GPS device is required to be controlled within + -0.5 ppm, and wireless applications such as Wifi and Bluetooth only allow the frequency offset to be within + -10 ppm. Therefore, it is important to reduce the influence of external stress on the frequency of the acoustic wave resonator.
However, the existing film bulk acoustic wave filter and oscillator generally have more layers of growing materials, the process is complex, the external stress is easily transmitted to the resonator, the frequency deviation is serious, and the influence of the external stress on the frequency of the acoustic wave resonator cannot be effectively reduced.
Disclosure of Invention
Technical problem to be solved
The present disclosure provides a film bulk acoustic resonator, a method for manufacturing the same, and a filter, so as to at least partially solve the above technical problems.
(II) technical scheme
According to an aspect of the present disclosure, there is provided a thin film bulk acoustic resonator including:
a substrate, and
a piezoelectric stack structure formed on the substrate;
wherein a center pillar structure is formed at an eccentric position of the film bulk acoustic resonator, and a cavity is formed around the center pillar structure.
In some embodiments, the piezoelectric stack includes a lower electrode layer, an upper electrode layer, and a piezoelectric layer between the lower and upper electrode layers; the lower electrode and the substrate enclose the cavity.
In some embodiments, the piezoelectric stack includes a lower electrode layer, an upper electrode layer, and a piezoelectric layer between the lower and upper electrode layers; the film bulk acoustic resonator further comprises a conductive layer formed between the substrate and the lower electrode layer, and the cavity is formed between the lower electrode and the conductive layer.
In some embodiments, the lower electrode layer comprises a first lower electrode and a second lower electrode;
the first lower electrode comprises a first part, a second part, a third part and a fourth part which are connected in sequence, wherein the first part and the fourth part are in contact with the substrate, the first part and the third part extend along the direction parallel to the substrate, and the second part and the fourth part extend along the direction vertical to the substrate;
the second lower electrode comprises a first part, a second part, a third part, a fourth part and a fifth part which are connected in sequence, wherein the first part and the fifth part of the second lower electrode are in contact with the substrate, the first part, the third part and the fifth part of the second lower electrode extend along a direction parallel to the substrate, and the second part and the fourth part of the second lower electrode extend along a direction perpendicular to the substrate.
In some embodiments, the piezoelectric layer comprises a first piezoelectric film and a second piezoelectric film, the first piezoelectric film completely covering the fourth portion of the first lower electrode and completely covering or partially covering the third portion of the first lower electrode;
the second piezoelectric film partially covers the first portion of the second lower electrode, completely covers the second portion of the second lower electrode, and completely covers or partially covers the third portion of the second lower electrode.
In some embodiments, the upper electrode layer comprises:
a first portion extending in a direction perpendicular to a substrate, a bottom portion of which is in contact with both the substrate and a first portion of the second lower electrode, and the first portion of the upper electrode layer is located between the first piezoelectric film and the second piezoelectric film;
a second portion on the piezoelectric layer extending in a direction parallel to the substrate.
In some embodiments, the thin film bulk acoustic resonator further comprises a spacer layer, the spacer layer comprising a first spacer film and a second spacer film;
the first spacer film is located between the first piezoelectric film and the upper electrode layer, and has a bottom in contact with the substrate; the second diaphragm is positioned between the second piezoelectric film and the upper electrode layer, and the bottom of the second diaphragm is in contact with the first part of the second lower electrode; or
The first spacer film is located between the first lower electrode and the first piezoelectric film, and has a bottom in contact with the substrate; the second diaphragm is located between the second lower electrode and the second piezoelectric film, and has a bottom portion in contact with a first portion of the second lower electrode.
In some embodiments, the film bulk acoustic resonator further includes a first bump and a second bump;
a first projection located between the upper electrode layer and the first piezoelectric film and located at one end of the second portion of the upper electrode layer; or a first protrusion is located between the first piezoelectric film and the third portion of the first lower electrode, and at one end of the first piezoelectric film;
the second protrusion is located between the upper electrode layer and the second piezoelectric film and at the other end of the second portion of the upper electrode layer; or a second protrusion is located between the second piezoelectric film and the third portion of the second lower electrode and at an end portion of the second piezoelectric film.
In some embodiments, the film bulk acoustic resonator further includes a pad layer on the upper electrode layer and the lower electrode layer.
In some embodiments, the pad layer partially covers the second portion of the upper electrode layer, the first portion of the first lower electrode, and the fifth portion or the first portion of the second lower electrode.
In some embodiments, the conductive layer comprises a first conductive film and a second conductive film; the lower electrode layer comprises a first lower electrode and a second lower electrode; the first lower electrode comprises a first part and a second part which are connected; a first part of the first lower electrode extends along a direction parallel to the substrate, a second part of the first lower electrode extends along a direction vertical to the substrate and is in contact with the substrate, and a gap is formed between the first part of the first lower electrode and the first conductive film; the second lower electrode extends along the direction parallel to the substrate, and a gap is formed between the second lower electrode and the second conductive film;
the piezoelectric layer includes a first piezoelectric film and a second piezoelectric film, the first piezoelectric film completely covering the first portion and the second portion of the first lower electrode; the second piezoelectric film completely covers the second lower electrode;
the upper electrode layer includes: a first portion extending in a direction perpendicular to a substrate, a bottom portion of which is in contact with both the substrate and the second conductive film, and a first portion of the upper electrode layer is located between the first piezoelectric film and the second piezoelectric film; and a second portion on the piezoelectric layer extending in a direction parallel to the substrate;
the thin film bulk acoustic resonator further comprises a spacing layer, wherein the spacing layer comprises a first spacing film and a second spacing film; the first spacer film is located between the first piezoelectric film and the upper electrode layer, and has a bottom in contact with the substrate; the second spacer film is located between the second piezoelectric film and the upper electrode, and has a bottom portion in contact with the second conductive film.
In some embodiments, the piezoelectric layer includes a first piezoelectric film formed on a third portion of the first lower electrode and a second piezoelectric film formed on a third portion of the second lower electrode;
the upper electrode layer includes: a first portion extending in a direction perpendicular to a substrate, a bottom portion of which is in contact with both the substrate and a first portion of the second lower electrode, and the first portion of the upper electrode layer is located between the first piezoelectric film and the second piezoelectric film and between a fourth portion of the first lower electrode and a second portion of the second lower electrode; and a second portion on the piezoelectric layer extending in a direction parallel to the substrate;
the thin film bulk acoustic resonator further comprises a spacing layer, wherein the spacing layer comprises a first spacing film and a second spacing film; the bottom of the first spacer film is in contact with the substrate, and completely covers a fourth portion of the first lower electrode, partially covers a third portion of the first lower electrode, and partially covers the first piezoelectric film; the bottom of the first spacer film is in contact with the first portion of the second lower electrode, and completely covers the second portion of the second lower electrode, partially covers the third portion of the second lower electrode, and partially covers the second piezoelectric film.
In some embodiments, the king post structure comprises: a portion of the upper electrode layer perpendicular to the substrate, a portion of the spacer layer perpendicular to the substrate, a portion of the piezoelectric layer perpendicular to the substrate, a portion of the lower electrode layer perpendicular to the substrate and proximate to the spacer layer.
According to another aspect of the present disclosure, there is also provided a method for manufacturing a thin film bulk acoustic resonator, including:
growing a sacrificial layer on the substrate and carrying out patterning treatment to form a first opening region;
growing a lower electrode layer and etching the lower electrode layer, and forming a second opening region in the first opening region;
growing a piezoelectric layer and an upper electrode layer;
etching the upper electrode layer and the piezoelectric layer, and forming a third opening area in the second opening area;
and etching to remove the sacrificial layer, and forming a cavity between the lower electrode and the substrate and in an effective resonance area of the film bulk acoustic resonator.
In some embodiments, the method further includes growing an isolation layer between the lower electrode layer and the piezoelectric layer or between the piezoelectric layer and the upper electrode layer, and performing an imaging process.
In some embodiments, before growing the sacrificial layer, growing a conductive layer and performing an imaging process.
In some embodiments, the method further comprises forming a bump structure between the lower electrode layer and the piezoelectric layer or between the piezoelectric layer and the upper electrode layer.
According to still another aspect of the present disclosure, there is also provided a filter including a plurality of the thin film bulk acoustic resonators in cascade.
(III) advantageous effects
According to the technical scheme, the film bulk acoustic resonator, the manufacturing method thereof and the filter have at least one of the following beneficial effects:
(1) the method and the device reduce the influence of external stress on the resonant frequency of the device, and are suitable for application with higher frequency stability requirements.
(2) The disclosed process is relatively simple, does not need Chemical Mechanical Polishing (CMP) treatment on the sacrificial layer, and can reduce the number of layers of the grown material, thereby reducing the manufacturing cost
(3) The pad structure of the present disclosure can reduce the connection resistance, and the first pad is located the center pillar region simultaneously, can reinforce the center pillar structure. In addition, the two ends of the first bonding pad are positioned at the boundary of the resonance effective area, so that sound waves of the resonance device at the edge can be reflected to the effective resonance area, and the Q value of the device is improved.
Drawings
Fig. 1 is a front cross-sectional view of a thin film bulk acoustic wave device according to embodiment 1 of the present disclosure.
Fig. 2 is a top view of a thin film bulk acoustic wave device according to embodiment 1 of the present disclosure.
Fig. 3 is a front cross-sectional view of a thin film bulk acoustic wave device according to embodiment 2 of the present disclosure.
Fig. 4 is a front cross-sectional view of a thin film bulk acoustic wave device according to embodiment 3 of the present disclosure.
Fig. 5 is a front cross-sectional view of a thin film bulk acoustic wave device according to embodiment 4 of the present disclosure.
FIG. 6 is a flow chart of a method for fabricating a thin film bulk acoustic wave device according to the present disclosure.
Fig. 7a-7 h are schematic diagrams illustrating a process of fabricating a thin film bulk acoustic wave device according to the present disclosure.
< description of symbols >
1-a substrate; 2-sacrificial layer (sacrificial layer region corresponds to cavity region); 3-a lower electrode layer; 31-a first lower electrode, 32-a second lower electrode; 311-314 are the first to fourth portions of the first lower electrode, respectively; 321-325 are the first to fifth portions of the second bottom electrode, respectively; 4-a piezoelectric layer; 41-a first piezoelectric film, 42-a second piezoelectric film; 5-a spacer layer; 51-a first spacer film, 52-a second spacer film; 6-upper electrode layer; 61-a first portion of the upper electrode layer, 62-a second portion of the upper electrode layer; 7-a conductive layer; 71-a first conductive film, 72-a second conductive film; 8-a raised structure; 81-first bump, 82-second bump; 9-a pad layer; 91-first pad, 92-second pad, 93-third pad; o-center pillar position.
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 thin film bulk acoustic resonator, including:
a substrate, and
a piezoelectric stack structure formed on the substrate;
wherein a center pillar structure is formed at an eccentric position of the film bulk acoustic resonator, and a cavity is formed around the center pillar structure.
The film bulk acoustic resonator reduces the influence of external stress on the resonant frequency of the device, and is suitable for application with higher frequency stability requirements.
Specifically, the piezoelectric stack structure includes: a lower electrode layer, an upper electrode layer, and a piezoelectric layer located between the lower electrode layer and the upper electrode layer; the lower electrode layer and the substrate enclose the cavity.
The center pillar structure is a cylindrical structure that plays a supporting role in the bulk acoustic wave resonator, and includes: a portion of the upper electrode layer perpendicular to the substrate, a portion of the spacer layer perpendicular to the substrate, a portion of the piezoelectric layer perpendicular to the substrate, a portion of the lower electrode layer perpendicular to the substrate and proximate to the spacer layer.
Further, the film bulk acoustic resonator may further include a conductive layer formed between the substrate and the lower electrode layer, and the cavity is formed between the lower electrode layer and the conductive layer.
The lower electrode layer comprises a first lower electrode and a second lower electrode; the first lower electrode comprises a first part, a second part, a third part and a fourth part which are connected in sequence, wherein the first part and the fourth part are in contact with the substrate, the first part and the third part extend along the direction parallel to the substrate, and the second part and the fourth part extend along the direction vertical to the substrate; the second lower electrode comprises a first part, a second part, a third part, a fourth part and a fifth part which are connected in sequence, wherein the first part and the fifth part of the second lower electrode are in contact with the substrate, the first part, the third part and the fifth part of the second lower electrode extend along a direction parallel to the substrate, and the second part and the fourth part of the second lower electrode extend along a direction perpendicular to the substrate.
The piezoelectric layer includes a first piezoelectric film and a second piezoelectric film, the first piezoelectric film completely covers the fourth portion of the first lower electrode and completely covers or partially covers the third portion of the first lower electrode; the second piezoelectric film partially covers the first portion of the second lower electrode, completely covers the second portion of the second lower electrode, and completely covers or partially covers the third portion of the second lower electrode.
The upper electrode layer includes: a first portion extending in a direction perpendicular to a substrate, a bottom portion of which is in contact with both the substrate and a first portion of the second lower electrode, and the first portion of the upper electrode layer is located between the first piezoelectric film and the second piezoelectric film; a second portion on the piezoelectric layer extending in a direction parallel to the substrate.
The film bulk acoustic resonator further comprises a pad layer positioned on the upper electrode layer and the lower electrode layer. Specifically, the pad layer is located on a second portion of the upper electrode layer (a portion of the upper electrode layer perpendicular to the substrate, a portion of the spacer layer perpendicular to the substrate, a portion of the piezoelectric layer perpendicular to the substrate, a portion of the lower electrode layer perpendicular to the substrate and near the spacer layer), a first portion of the first lower electrode, and a fifth portion of the second lower electrode, and partially covers the second portion of the upper electrode layer, the first portion of the first lower electrode, and the fifth portion of the second lower electrode. If the center pillar is wider and the upper electrode does not entirely cover the first portion of the second lower electrode, the pad layer may also contact the first portion of the second lower electrode to further reduce resistive loss.
The spacing layer comprises a first spacing film and a second spacing film; the first spacer film is located between the first piezoelectric film and the upper electrode layer, and has a bottom in contact with the substrate; the second diaphragm is positioned between the second piezoelectric film and the upper electrode layer, and the bottom of the second diaphragm is in contact with the first part of the second lower electrode; or the first spacer film is positioned between the first lower electrode and the first piezoelectric film, and the bottom of the first spacer film is in contact with the substrate; the second diaphragm is located between the second lower electrode and the second piezoelectric film, and has a bottom portion in contact with a first portion of the second lower electrode.
The film bulk acoustic resonator can also comprise a first bump and a second bump; a first projection located between the upper electrode layer and the first piezoelectric film and located at one end of the second portion of the upper electrode layer; or a first protrusion is located between the first piezoelectric film and the third portion of the first lower electrode, and at one end of the first piezoelectric film; the second protrusion is located between the upper electrode layer and the second piezoelectric film and at the other end of the second portion of the upper electrode layer; or a second protrusion is located between the second piezoelectric film and the third portion of the second lower electrode and at an end portion of the second piezoelectric film.
Fig. 1 is a front cross-sectional view of a thin film bulk acoustic wave device according to embodiment 1 of the present disclosure. As shown in fig. 1, the film bulk acoustic wave device of the present embodiment includes: a substrate 1, a sacrificial layer 2, a lower electrode layer 3, a piezoelectric layer 4, a spacer layer 5, an upper electrode layer 6 and a pad 9.
The sacrificial layer of the thin film bulk acoustic wave device of the present disclosure is etched away at last, that is, the thin film bulk acoustic wave device manufactured finally does not include the sacrificial layer, and the sacrificial layer region correspondingly forms the cavity region, thereby forming the device supported by the middle pillar. The film bulk acoustic wave device of the present embodiment has a disk-like shape, and resonates by a sandwich structure of upper electrode layer-piezoelectric layer-lower electrode layer.
Fig. 2 is a top view of a thin film bulk acoustic wave device according to embodiment 1 of the present disclosure. As shown in fig. 1-2, the lower electrode layer is etched into a first lower electrode 31 and a second lower electrode 32. Wherein the first lower electrode 31 is drawn out through the edge portion, and the upper electrode layer is connected to the second lower electrode 32 through the center pillar, thereby being drawn out through the edge, contributing to reducing the effect of external stress on the device, thereby reducing the frequency shift.
The first lower electrode 31 includes a first portion 311, a second portion 312, a third portion 313 and a fourth portion 314 connected in sequence, where the first portion and the fourth portion are in contact with the substrate, the first portion and the third portion extend in a direction parallel to the substrate, and the second portion and the fourth portion extend in a direction perpendicular to the substrate.
The second lower electrode 32 includes a first portion 321, a second portion 322, a third portion 323, a fourth portion 324, and a fifth portion 325, which are connected in sequence, wherein the first portion, the third portion, and the fifth portion of the second lower electrode are in contact with the substrate, the first portion, the third portion, and the fifth portion of the second lower electrode extend in a direction parallel to the substrate, and the second portion and the fourth portion of the second lower electrode extend in a direction perpendicular to the substrate.
The piezoelectric layer 4 includes a first piezoelectric film 41 and a second piezoelectric film 42. The first piezoelectric film completely covers the fourth portion of the first lower electrode and partially covers the third portion of the first lower electrode. The second piezoelectric film partially covers the first portion of the second lower electrode, completely covers the second portion of the second lower electrode, and partially covers the third portion of the second lower electrode.
The upper electrode layer 6 comprises a first portion 61 and a second portion 62. The first portion 61 extends in a direction perpendicular to the substrate, the bottom thereof is in contact with both the substrate and the first portion of the second lower electrode, and the first portion of the upper electrode layer is located between the first piezoelectric film and the second piezoelectric film. The second portion 62 is located on the piezoelectric layer and extends in a direction parallel to the substrate.
The thin film bulk acoustic resonator further comprises a spacer layer 5 comprising a first spacer film 51 and a second spacer film 52. The first spacer film is located between the first piezoelectric film and the upper electrode layer, and has a bottom in contact with the substrate; the second separator is located between the second piezoelectric film and the upper electrode layer, and has a bottom in contact with a first portion of the second lower electrode.
The film bulk acoustic resonator further comprises a pad layer 9, wherein the pad layer comprises a first pad 91, a second pad 92 and a third pad 93, the pad layer is positioned on the second part of the upper electrode layer, the first part of the first lower electrode and the fifth part of the second lower electrode, and the pad layer partially covers the second part of the upper electrode layer, the first part of the first lower electrode and the fifth part of the second lower electrode. The film bulk acoustic resonator further includes a bump structure including a first bump 81 and a second bump 82. The first protrusion is located between the upper electrode and the first piezoelectric film and at one end of the second portion of the upper electrode layer. The second protrusion is located between the upper electrode layer and the second piezoelectric film and at another end of the second portion of the upper electrode layer.
The center pillar structure includes: a portion 61 of the upper electrode layer perpendicular to the substrate, a portion of the spacer layer perpendicular to the substrate, a portion of the piezoelectric layer perpendicular to the substrate, and a portion of the lower electrode layer perpendicular to the substrate and near the spacer layer (i.e., a fourth portion of the first lower electrode).
The substrate is made of silicon or a material with low heat conduction property; the material of the sacrificial layer includes but is not limited to silicon dioxide, silicon phosphorus glass (PSG), and the like; the lower electrode layer and the upper electrode layer are made of conductive materials, such as aluminum, molybdenum, copper, gold, platinum, silver, nickel, chromium, tungsten and the like which are compatible with a semiconductor process; materials of the piezoelectric layer include, but are not limited to, aluminum nitride, oxidizing, and the like; the material of the spacing layer is a dielectric material, such as PSG, or other materials which are not easy to etch; the bonding pad is made of high-conductivity materials such as aluminum, copper, gold, platinum, silver, nickel, chromium and the like which are compatible with semiconductor technology.
The effective resonance area of the resonator is located in the disc, and the upper electrode is located in the area opposite to the lower electrode. And in the central column region, a spacing layer is introduced to reduce the influence of parasitic capacitance of the upper and lower electrodes in the region and isolate the upper and lower electrodes. Thus, no resonance occurs in the center pillar region, and the displacement is small, thereby reducing the transmission of external force into the device. Meanwhile, the spacer layer also naturally forms a convex structure 8 (the convex structure and the spacer layer are made of the same material) at the edge of the resonant effective area, so that the sound waves of the resonant device at the edge can be reflected back to the effective area, and the Q value of the device is improved.
It should be noted that, as shown in fig. 2, the center pillar position O is offset from the center of the disk, and thus, the resonance caused by the transverse mode is suppressed, and the performance of the filter and the oscillator is improved.
Fig. 3 is a front cross-sectional view of a thin film bulk acoustic wave device according to embodiment 2 of the present disclosure. Unlike embodiment 1, this embodiment first grows a conductive layer 7 (similar in material to the lower electrode) on the substrate, and then grows subsequent layers similar to embodiment 1. In contrast, the first lower electrode of the device comprises two portions, one of which is parallel to the substrate and the other of which is perpendicular to the substrate; the second lower electrode includes a portion parallel to the substrate; the lower electrode and the upper electrode of the device are led out through the first conductive film 71 and the second conductive film 72 of the conductive layer, respectively, and therefore, the device is completely supported by the center pillar, further reducing the stress influence by the lead-out wire in embodiment 1. But also the reliability of the device may be inferior to that of the structure of embodiment 1 because it is supported only by the center pillars.
In this embodiment, the center pillar structure includes: a portion 61 of the upper electrode layer perpendicular to the substrate, a portion of the spacer layer perpendicular to the substrate, a portion of the piezoelectric layer perpendicular to the substrate, and a portion of the lower electrode layer perpendicular to the substrate and proximate to the spacer layer.
Fig. 4 is a front cross-sectional view of a thin film bulk acoustic wave device according to embodiment 3 of the present disclosure. Unlike embodiment 1, after etching the piezoelectric layer, the piezoelectric layer does not remain in the center pillar region. This further reduces the effect of parasitic capacitance in the newel area.
Fig. 5 is a front cross-sectional view of a thin film bulk acoustic wave device according to embodiment 4 of the present disclosure. In embodiment 1, the spacer layer is located between the upper electrode and the piezoelectric layer, while in embodiment 4, the spacer layer may also be located between the lower electrode and the piezoelectric layer. The convex structure at the edge can reflect the sound wave of the resonant device at the edge back to the effective area, so that the Q value of the device is improved.
Of course, the device structure of the present disclosure is not limited to a disk shape, and may be an ellipse, a pentagon or other irregular polygon, but should be avoided as a regular polygon, so that the resonance effect of the transverse mode can be reduced as well.
Fig. 6 is a flowchart illustrating a method for fabricating a thin film bulk acoustic wave device according to embodiment 2 of the present disclosure. Fig. 7a-7g are schematic diagrams illustrating a process of fabricating a thin film bulk acoustic wave device according to embodiment 2 of the disclosure. As shown in fig. 6 and fig. 7a to 7g, the specific manufacturing process of the film bulk acoustic wave device is as follows:
as shown in fig. 7a, a conductive layer is first deposited on the surface of the substrate, and is patterned to separate the conductive layer into a first conductive film and a second conductive film for leading out the lower electrode and the upper electrode of the device, respectively;
as shown in fig. 7b, a sacrificial layer is deposited on the substrate, covering the conductive layer, and patterned to define the locations of the center posts. Exposing a part of the conductive layer in the central pillar area so as to make electrical connection later;
as shown in fig. 7c, a lower electrode layer is deposited and patterned as well; making the lower electrode layer leave a hole in the center pillar region, and connecting the lower electrode layer with the first conductive film of the conductive layer; before depositing the bottom electrode layer, a thin isolation layer is typically grown to isolate oxygen migration from the sacrificial layer to the bottom electrode layer. In addition, a temperature compensation layer can be selectively inserted into or grown on the surface of the lower electrode layer, and the material of the temperature compensation layer is silicon dioxide or PSG and other materials with positive temperature coefficients;
depositing a piezoelectric layer and patterning to expose the conductive layer in the edge and center pillar areas for top electrode extraction, as shown in figure 7 d;
as shown in fig. 7e, a spacer layer is deposited, exposing the edge and center pillar regions. Meanwhile, a spacer layer pattern is reserved in the edge area of the disc, and a formed convex structure can reflect the sound waves of the resonant device at the edge back to the effective resonant area, so that the Q value of the device is improved;
as shown in fig. 7f, an upper electrode layer is deposited for patterning. The upper electrode is drawn out through the second conductive film of the conductive layer (as shown). Once the upper electrode is formed, the device forms an effective resonance area from the facing areas of the upper and lower electrodes. In addition, a passivation layer is generally grown on the surface of the upper electrode layer to protect the electrode from corrosion;
as shown in fig. 7g, a pad layer is deposited, patterning process. The pads include a first pad over the upper electrode layer, a second pad over a first portion of the first lower electrode, and a third pad over a fifth portion or first portion of the second lower electrode. The pad structure of the present disclosure can reduce the connection resistance, and the first pad is located the center pillar region simultaneously, can reinforce the center pillar structure. In addition, two ends of the first bonding pad are positioned at the boundary of the resonance effective area, so that sound waves at the edge of the resonance device can be reflected to the effective resonance area, and the Q value of the device is improved;
as shown in fig. 7h, the device is placed in an etchant, the sacrificial layer is etched away, releasing the device. Finally, the device is supported only by the center pillar structure, and the effect of external stress on the device can be reduced.
The disclosed process is relatively simple, does not require Chemical Mechanical Polishing (CMP) of the sacrificial layer, and can also reduce the number of layers of the grown material, which all reduce the manufacturing cost.
In addition, the disclosure also provides a filter which comprises a plurality of thin film bulk acoustic resonators which are cascaded.
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.
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 (9)

1. A thin film bulk acoustic resonator comprising:
a substrate, and
a piezoelectric stack structure formed on the substrate;
a center pillar structure is formed at an eccentric position of the film bulk acoustic resonator, and a cavity is formed around the center pillar structure;
wherein the piezoelectric stack structure comprises a lower electrode layer, an upper electrode layer and a piezoelectric layer located between the lower electrode layer and the upper electrode layer; the lower electrode and the substrate enclose the cavity;
wherein the lower electrode layer comprises a first lower electrode and a second lower electrode;
the first lower electrode comprises a first part, a second part, a third part and a fourth part which are connected in sequence, wherein the first part and the fourth part are in contact with the substrate, the first part and the third part extend along the direction parallel to the substrate, and the second part and the fourth part extend along the direction vertical to the substrate;
the second lower electrode comprises a first part, a second part, a third part, a fourth part and a fifth part which are connected in sequence, wherein the first part and the fifth part of the second lower electrode are in contact with the substrate, the first part, the third part and the fifth part of the second lower electrode extend along a direction parallel to the substrate, and the second part and the fourth part of the second lower electrode extend along a direction perpendicular to the substrate.
2. The thin film bulk acoustic resonator of claim 1, wherein the piezoelectric stack structure comprises a lower electrode layer, an upper electrode layer, and a piezoelectric layer between the lower and upper electrode layers; the film bulk acoustic resonator further comprises a conductive layer formed between the substrate and the lower electrode layer, and the cavity is formed between the lower electrode and the conductive layer.
3. The thin film bulk acoustic resonator of claim 1,
the piezoelectric layer includes a first piezoelectric film and a second piezoelectric film, the first piezoelectric film completely covers the fourth portion of the first lower electrode and completely covers or partially covers the third portion of the first lower electrode;
the second piezoelectric film partially covers the first portion of the second lower electrode, completely covers the second portion of the second lower electrode, and completely covers or partially covers the third portion of the second lower electrode.
4. The thin film bulk acoustic resonator of claim 3, wherein the upper electrode layer comprises:
a first portion extending in a direction perpendicular to a substrate, a bottom portion of which is in contact with both the substrate and a first portion of the second lower electrode, and the first portion of the upper electrode layer is located between the first piezoelectric film and the second piezoelectric film;
a second portion on the piezoelectric layer extending in a direction parallel to the substrate.
5. The thin film bulk acoustic resonator of claim 4, further comprising a spacer layer, the spacer layer comprising a first spacer film and a second spacer film;
the first spacer film is located between the first piezoelectric film and the upper electrode layer, and has a bottom in contact with the substrate; the second diaphragm is positioned between the second piezoelectric film and the upper electrode layer, and the bottom of the second diaphragm is in contact with the first part of the second lower electrode; or
The first spacer film is located between the first lower electrode and the first piezoelectric film, and has a bottom in contact with the substrate; the second diaphragm is located between the second lower electrode and the second piezoelectric film, and has a bottom portion in contact with a first portion of the second lower electrode.
6. The thin film bulk acoustic resonator of claim 3, further comprising a first bump and a second bump;
a first projection located between the upper electrode layer and the first piezoelectric film and located at one end of the second portion of the upper electrode layer; or a first protrusion is located between the first piezoelectric film and the third portion of the first lower electrode, and at one end of the first piezoelectric film;
the second protrusion is located between the upper electrode layer and the second piezoelectric film and at the other end of the second portion of the upper electrode layer; or a second protrusion is located between the second piezoelectric film and the third portion of the second lower electrode and at an end portion of the second piezoelectric film.
7. The film bulk acoustic resonator according to claim 3, further comprising a pad layer on the upper electrode layer and the lower electrode layer,
wherein the pad layer partially covers the second portion of the upper electrode layer, the first portion of the first lower electrode, and the fifth portion or the first portion of the second lower electrode.
8. A method for manufacturing a film bulk acoustic resonator comprises the following steps:
growing a sacrificial layer on the substrate and carrying out patterning treatment to form a first opening region;
growing a lower electrode layer and etching the lower electrode layer, and forming a second opening region in the first opening region;
growing a piezoelectric layer and an upper electrode layer;
etching the upper electrode layer and the piezoelectric layer, and forming a third opening area in the second opening area;
etching to remove the sacrificial layer, and forming a cavity between the lower electrode and the substrate and in an effective resonance area of the film bulk acoustic resonator;
wherein the lower electrode layer comprises a first lower electrode and a second lower electrode;
the first lower electrode comprises a first part, a second part, a third part and a fourth part which are connected in sequence, wherein the first part and the fourth part are in contact with the substrate, the first part and the third part extend along the direction parallel to the substrate, and the second part and the fourth part extend along the direction vertical to the substrate;
the second lower electrode comprises a first part, a second part, a third part, a fourth part and a fifth part which are connected in sequence, wherein the first part and the fifth part of the second lower electrode are in contact with the substrate, the first part, the third part and the fifth part of the second lower electrode extend along a direction parallel to the substrate, and the second part and the fourth part of the second lower electrode extend along a direction perpendicular to the substrate.
9. A filter comprising a plurality of thin film bulk acoustic resonators as claimed in any one of claims 1 to 6 in cascade.
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