# US 2019/0356293 A1 · Bulk acoustic wave resonator and method of manufacturing the same

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- Number: US 2019/0356293 A1
- Document ID: US20190356293A1
- Status: Published application
- Kind: A1
- Application number: 16/400,052
- Filed: 2019-05-01
- Published: 2019-11-21
- Earliest claimed: 2018-05-17
- Assignees: Samsung Electro-Mechanics Co., Ltd.
- Applicants: Samsung Electro-Mechanics Co., Ltd.
- Inventors: Yong Suk KIM; Moon Chul LEE; Sung Jun LEE; Chang Hyun LIM; Jae Hyoung GIL; Sang Hyun YI
- Web page: https://patentgrep.com/patent/US20190356293A1

## CPC

- H03H 3/04: for obtaining desired frequency or temperature coefficient
- H03H 9/02086: {Means for compensation or elimination of undesirable effects}
- H03H 3/02: for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence)
- H03H 9/132: {characterized by a particular shape}
- H03H 9/173: {Air-gaps}
- H03H 9/174: {Membranes}
- H03H 9/175: {Acoustic mirrors}
- H03H 9/54: comprising resonators of piezoelectric or electrostrictive material (comprising resonators using surface acoustic waves H03H9/64)
- H03H 2003/021: {the resonators or networks being of the air-gap type}
- H03H 2003/0442: {of a non-piezoelectric layer}
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)

## Abstract

A bulk acoustic wave resonator includes a substrate; a lower electrode disposed on the substrate; a piezoelectric layer disposed to cover at least a portion of the lower electrode; an upper electrode disposed to cover at least a portion of the piezoelectric layer; and a passivation layer disposed to cover at least a portion of the upper electrode, wherein the passivation layer includes a non-trimming-processed portion disposed outside an active region of the bulk acoustic wave resonator in which portions of the lower electrode, the piezoelectric layer, and the upper electrode overlap, and having a thickness that is thicker than a thickness of a portion of the passivation layer disposed in the active region.

## Claims

### Claim 1

A bulk acoustic wave resonator comprising:
a substrate;
a lower electrode disposed on the substrate;
a piezoelectric layer disposed to cover at least a portion of the lower electrode;
an upper electrode disposed to cover at least a portion of the piezoelectric layer; and
a passivation layer disposed to cover at least a portion of the upper electrode,
wherein the passivation layer comprises a non-trimming-processed portion disposed outside an active region of the bulk acoustic wave resonator in which portions of the lower electrode, the piezoelectric layer, and the upper electrode overlap, and having a thickness that is thicker than a thickness of a portion of the passivation layer disposed in the active region.

### Claim 2 (depends on 1)

The bulk acoustic wave resonator of claim 1, wherein the portion of the passivation layer disposed in the active region has a uniform thickness.

### Claim 3 (depends on 1)

The bulk acoustic wave resonator of claim 1, wherein the passivation layer further comprises a connection region connecting the portion of the passivation layer disposed in the active region to the non-trimming-processed portion of the passivation layer, and
a width of the connection region is 1 μm or less.

### Claim 4 (depends on 1)

The bulk acoustic wave resonator of claim 1, further comprising a metal pad disposed at least on a portion of the lower electrode or a portion of the upper electrode,
wherein the non-trimming-processed portion is disposed between the metal pad and the active region.

### Claim 5 (depends on 1)

The bulk acoustic wave resonator of claim 1, wherein the passivation layer is a dielectric layer comprising any one of silicon nitride (Si3N4), silicon oxide (SiO2), manganese oxide (MgO), zirconium oxide (ZrO2), aluminum nitride (AlN), lead zirconate titanate (PZT), gallium arsenide (GaAs), hafnium oxide (HfO2), aluminum oxide (Al2O3), titanium oxide (TiO2), and zinc oxide (ZnO).

### Claim 6 (depends on 1)

The bulk acoustic wave resonator of claim 1, wherein the non-trimming-processed portion is disposed to surround the active region.

### Claim 7 (depends on 1)

The bulk acoustic wave resonator of claim 1, further comprising an insertion layer disposed between the lower electrode and the piezoelectric layer.

### Claim 8 (depends on 1)

The bulk acoustic wave resonator of claim 1, further comprising:
a cavity disposed between the active region and the substrate, and
an etching prevention portion disposed to surround the cavity.

### Claim 9 (depends on 8)

The bulk acoustic wave resonator of claim 8, further comprising a sacrificial layer disposed to surround the etching prevention portion.

### Claim 10 (depends on 1)

The bulk acoustic wave resonator of claim 1, wherein the non-trimming-processed portion is adapted to be covered by a photoresist (PR) trimming mask formed of a photoresist during a trimming operation performed on the portion of the passivation layer disposed in the active region.

### Claim 11 (depends on 1)

The bulk acoustic wave resonator of claim 1, further comprising a gap disposed between the piezoelectric layer and the upper electrode,
wherein the active region extends to an end of the gap closest to a center of the bulk acoustic wave resonator.

### Claim 12 (depends on 11)

The bulk acoustic wave resonator of claim 11, wherein the piezoelectric layer comprises an etching groove disposed outside the active region.

### Claim 13 (depends on 11)

The bulk acoustic wave resonator of claim 11, wherein the substrate comprises a cavity-forming groove that forms a cavity under the active region.

### Claim 14 (depends on 1)

The bulk acoustic wave resonator of claim 1, wherein the lower electrode, the piezoelectric layer, and the upper electrode have a bent shape in the active region.

### Claim 15 (depends on 14)

The bulk acoustic wave resonator of claim 14, wherein the substrate and a portion of the lower electrode having the bent shape form a cavity together.

### Claim 16 (depends on 1)

The bulk acoustic wave resonator of claim 1, further comprising a reflection layer disposed on the substrate under the active region or in a groove formed in the substrate under the active region.

### Claim 17 (depends on 16)

The bulk acoustic wave resonator of claim 16, wherein the reflection layer comprises a first reflection member and a second reflection member disposed on the first reflection member, or
the reflection layer comprises a plurality of first reflection members and a plurality of second reflection members disposed in a stack so that the first reflection members alternate with the second reflection members with one of the first reflection members being disposed at one end of the stack and one of the second reflection members being disposed at an opposite end of the stack.

### Claim 18

A method of manufacturing a bulk acoustic wave resonator, the bulk acoustic wave resonator comprising a substrate, a lower electrode disposed to cover at least a portion of the substrate, a piezoelectric layer disposed to cover at least a portion of the lower electrode, an upper electrode disposed to cover at least a portion of the piezoelectric layer, and a passivation layer disposed to cover at least a portion of the upper electrode, the method comprising:
forming a photoresist (PR) trimming mask of a photoresist on a portion of the passivation layer disposed in a region of the bulk acoustic wave resonator in which a trimming operation is not to be performed on the passivation layer;
trimming a portion of the passivation layer disposed in a region of the bulk acoustic wave resonator in which the trimming operation is to be performed on the passivation layer; and
removing the PR trimming mask.

### Claim 19

A bulk acoustic wave resonator comprising:
a substrate;
a lower electrode disposed on at least a portion of the substrate;
a piezoelectric layer disposed on at least a portion of the lower electrode;
an upper electrode disposed on at least a portion of the piezoelectric layer; and
a passivation layer disposed on at least a portion of the upper electrode,
wherein portions of the lower electrode, the piezoelectric layer, and the upper electrode overlap to form an active region of the bulk acoustic wave resonator,
the passivation layer comprises:
a first portion disposed outside the active region and having a first thickness; and
a second portion disposed in the active region and having a second thickness less than the first thickness, and
a transition between the first thickness and the second thickness occurs over a distance that is sufficiently small to prevent an abnormal region of amplitude fluctuation caused by the transition from occurring in a resonator waveform of the bulk acoustic wave resonator.

### Claim 20 (depends on 19)

The bulk acoustic wave resonator of claim 19, wherein the transition between the first thickness and the second thickness occurs over a distance that is substantially equal to zero so that there is a step difference between the first thickness and the second thickness.

### Claim 21 (depends on 19)

The bulk acoustic wave resonator of claim 19, wherein the transition between the first thickness and the second thickness occurs over a distance of 1 μm or less.

### Claim 22 (depends on 19)

The bulk acoustic wave resonator of claim 19, wherein the second thickness determines an operating frequency of the bulk acoustic wave resonator.

### Claim 23

A method of manufacturing a bulk acoustic wave resonator, the bulk acoustic wave resonator comprising a substrate, a lower electrode disposed on at least a portion of the substrate, a piezoelectric layer disposed on at least a portion of the lower electrode, an upper electrode disposed on at least a portion of the piezoelectric layer, and a passivation layer disposed on at least a portion of the upper electrode, wherein portions of the lower electrode, the piezoelectric layer, and the upper electrode overlap to form an active region of the bulk acoustic wave resonator, the method comprising:
disposing a trimming mask on the bulk acoustic wave resonator so that
there is no gap between the trimming mask and any portion of the bulk acoustic wave resonator on which the trimming mask is disposed,
the trimming mask covers a first portion of the passivation layer disposed in a first region of the bulk acoustic wave resonator in which a trimming operation is not to be performed on the passivation layer, and
the trimming mask does not cover a second portion of the passivation layer in a second region of the bulk acoustic wave resonator in which the trimming operation is to be performed on the passivation layer;
trimming only the second portion of the passivation layer using the trimming mask; and
removing the trimming mask.

### Claim 24 (depends on 23)

The method of claim 23, wherein the first portion of the passivation layer is disposed outside the active region, and the second portion of the passivation layer is disposed in the active region.

### Claim 25 (depends on 23)

The method of claim 23, wherein the disposing of the trimming mask comprises forming the trimming mask of a photoresist on the bulk acoustic wave resonator by a photolithography process.

### Claim 26 (depends on 23)

The method of claim 23, wherein the trimming of only the second portion of the passivation layer adjusts an operating frequency of the bulk acoustic wave resonator by reducing a thickness of the second portion of the passivation layer.