CN-121984475-A - Electroacoustic filter, multiplexer and method for manufacturing electroacoustic filter

Abstract

An improved electroacoustic SAW or BAW filter (EAF) with improved electrical and/or acoustic properties is provided. The filter has a first resonator (R1) in a first layer stack (LS 1) and a second resonator (R2) in a second layer stack (LS 2). The second layer stack differs from the first layer stack in at least one parameter selected from the number of layers, the thickness of the layers and the material of the layers.

Inventors

• NAPP MATTHIAS
• F. Kubat

Assignees

• RF360新加坡私人有限公司

Dates

Publication Date

20260505

Application Date

20190321

Priority Date

20180425

Claims (18)

1. 1. An electroacoustic filter comprising: a first surface acoustic wave SAW resonator, implemented in the first layer stack, A second SAW resonator implemented in the second layer stack, and A trench between the first SAW resonator and the second SAW resonator, Wherein the first SAW resonator and the second SAW resonator comprise an electrode structure in an electrode layer, The second layer stack differs from the first layer stack in at least one parameter selected from the group consisting of number of layers, thickness of layers and material of layers, and The first layer stack and the second layer stack include piezoelectric layers.
2. 2. An electroacoustic filter according to claim 1, wherein: the electro-acoustic filter has a ladder topology, The first SAW resonator is a series resonator, and The second SAW resonator is a parallel resonator.
3. 3. An electro-acoustic filter according to claim 1 or 2, wherein the first layer stack and the second layer stack comprise layers selected from a frequency temperature coefficient TCF layer, a trimming layer, a passivation layer.
4. 4. An electro-acoustic filter according to claim 1 or 2, wherein the first layer stack and the second layer stack comprise frequency temperature coefficient TCF layers, and the thickness of the TCF layers of the first layer stack is different from the thickness of the TCF layers of the second layer stack.
5. 5. An electro-acoustic filter according to claim 1 or 2, wherein the trench is arranged above the piezoelectric layers of the first layer stack and the second layer stack.
6. 6. An electro-acoustic filter as claimed in claim 1 or 2, wherein said first SAW resonator and said second SAW resonator are acoustically decoupled.
7. 7. An electro-acoustic filter as claimed in claim 1 or 2, wherein said first SAW resonator and said second SAW resonator are arranged on a common carrier.
8. 8. An electro-acoustic filter according to claim 1 or 2, wherein the first layer stack and/or the second layer stack has a piezoelectric material provided as a thin layer or as a bulk material.
9. 9. A multiplexer comprising an electroacoustic filter according to any of the preceding claims, wherein: the electroacoustic filter has a TX sub-filter and an RX sub-filter, The first SAW resonator is in the TX sub-filter and the second SAW resonator is in the RX sub-filter.
10. 10. The multiplexer of claim 9, being a diplexer, a quad or higher order multiplexer.
11. 11. A method of manufacturing an electroacoustic filter, comprising the steps of: Providing a first layer stack for a first surface acoustic wave SAW resonator, the first layer stack comprising a piezoelectric layer, Providing a second layer stack for a second SAW resonator, the second layer stack comprising a piezoelectric layer, A trench is provided between the first layer stack and the second layer stack, Decoupling the first layer stack from the second layer stack or decoupling at least one processing step for providing the first layer stack from a processing step for providing the second layer stack.
12. 12. The method according to claim 11, wherein: the electro-acoustic filter has a ladder topology, The first SAW resonator is a series resonator, and The second SAW resonator is a parallel resonator.
13. 13. The method according to claim 11 or 12, wherein the first layer stack and the second layer stack are provided with a layer selected from a frequency temperature coefficient, TCF, layer, a trimming layer, a passivation layer.
14. 14. The method according to claim 11 or 12, wherein the first layer stack and the second layer stack are provided with frequency temperature coefficient, TCF, layers and the thickness of the TCF layers of the first layer stack is different from the thickness of the TCF layers of the second layer stack.
15. 15. The method of claim 11 or 12, wherein the trench is arranged above the piezoelectric layers of the first layer stack and the second layer stack.
16. 16. A method as claimed in claim 11 or 12, wherein the first SAW resonator and the second SAW resonator are acoustically decoupled.
17. 17. A method as claimed in claim 11 or 12, wherein the first SAW resonator and the SAW second resonator are arranged on a common carrier.
18. 18. The method according to claim 11 or 12, wherein the first layer stack and/or the second layer stack has a piezoelectric material, which is provided as a thin layer or as a bulk material.

Description

Electroacoustic filter, multiplexer and method for manufacturing electroacoustic filter Technical Field The application is a divisional application of Chinese patent application with the application date of 2019, 3-21, the application number of 201980027686.4 and the name of 'an electroacoustic filter, a multiplexer and a method for manufacturing the electroacoustic filter'. The present invention relates to an electroacoustic filter that may be used in a mobile communication device, and to a multiplexer comprising such a filter. Furthermore, the present invention relates to an improved method of manufacturing an electroacoustic filter. Background An electroacoustic filter is an RF filter that uses sound waves in an electroacoustic resonator. Such a resonator comprises an electrode structure and a piezoelectric material for converting between RF signals and acoustic waves. The electro-acoustic filter may be a band pass filter or a band reject filter providing steep side edges. What is desired is an improved electroacoustic filter that is compatible with specifications of the next generation mobile communication system. In particular, good electrical and acoustic properties are desirable. For example, an electroacoustic filter with a small Temperature Coefficient of Frequency (TCF), a high electroacoustic coupling coefficient K 2 providing a wide bandwidth, and a reduced spurious mode in the critical frequency range is desirable. Furthermore, the electro-acoustic filter should be compatible with a Carrier Aggregation (CA) system. Conventional electroacoustic filters may include SAW resonators (saw=surface acoustic wave) or BAW resonators (baw=bulk acoustic wave). In RF filters employing SAW resonators, a TCF layer may be provided for reducing temperature induced changes in the characteristic frequency. However, conventional RF filters are optimized with respect to only one parameter or a small number of parameters. What is needed, therefore, is an electroacoustic filter that provides improved electrical and acoustic properties for various parameters. Disclosure of Invention For this purpose an electroacoustic filter and a method of manufacturing an electroacoustic filter and a multiplexer according to the independent claims are provided. The dependent claims provide preferred embodiments. The electro-acoustic filter includes a first resonator implemented in a first layer stack and a second resonator implemented in a second layer stack. The second layer stack differs from the first layer stack in at least one parameter selected from the number of layers, the thickness of the layers, and the material of the layers. The first resonator may be an electroacoustic resonator and the second resonator may be an electroacoustic resonator. For this purpose, the corresponding layer stack comprises a piezoelectric material and an electrode structure to convert between RF signals and acoustic waves using the piezoelectric effect when RF signals are applied to the electrode structure. The first layer stack and the second layer stack may have a similar configuration. In particular, it is possible that for each layer or layers of the first layer stack, there is a relevant layer in the second layer stack that has the same purpose as the relevant layer of the first stack. The difference between the first layer stack and the second layer stack or the number of differences between the first layer stack and the second layer stack corresponds to decoupling of the first resonator and the second resonator. The decoupling may be acoustic decoupling of the corresponding resonator or decoupling of at least one of the corresponding process steps of the method of manufacturing the resonator. Decoupling between the first resonator and the second resonator allows independent optimization for the first resonator and for the second resonator. The conventional RF filter includes a structure of a first resonator and a structure of a second resonator arranged adjacent to each other on a common carrier. Due to the constructional similarity of the first and second resonators in conventional filters, the manufacturing method is greatly simplified by creating corresponding layers for the first resonator and for the second resonator together using the same processing steps. However, this simplification in processing results in coupled resonators and/or coupled processing steps, which prevent the second resonator from being independent of the first resonator, and which prevent the corresponding electroacoustic filter from having good electrical and acoustic properties for a number of parameters. The proposed decoupling of the first resonator and the second resonator thus provides the possibility of optimizing the first resonator with respect to the first parameter and the second resonator with respect to the second parameter, so that the overall electroacoustic filter is optimized with respect to two or more parameters. It is possible that the first r