US-12627280-B2 - Increased dielectric film thickness reflector in a temperature compensated surface acoustic wave resonator

Abstract

Aspects and embodiments disclosed herein include an acoustic wave device comprising a substrate, a pair of IDT electrodes formed on the substrate, fingers of one IDT electrode arranged interleaved with fingers of the other IDT electrode, reflectors formed on the substrate, one of the reflectors being adjacent to one side of the pair of IDT electrodes and another reflector being adjacent to the opposite side of the pair of IDT electrodes so as to interpose the pair of IDT electrodes therebetween, the reflectors and the pair of IDT electrodes arranged along a propagation direction of a main acoustic wave, and a dielectric film covering the pair of IDT electrodes and the reflectors, the dielectric film having a first thickness covering at least a portion of the reflectors, the dielectric film having a second thickness covering the pair of IDT electrodes, the first thickness being different from the second thickness.

Inventors

• Satoru Ikeuchi
• Joji Fujiwara

Assignees

• SKYWORKS SOLUTIONS, INC.

Dates

Publication Date

20260512

Application Date

20240125

Claims (19)

1. 1 . An acoustic wave device comprising: a substrate; a pair of IDT electrodes formed on the substrate, each of the pair of IDT electrodes including a bus bar and a plurality of fingers extending from the bus bar, a respective finger of one IDT electrode arranged interleaved with respective fingers of the other IDT electrode; reflectors formed on the substrate, one of the reflectors being adjacent to one side of the pair of IDT electrodes and another reflector being adjacent to an opposite side of the pair of IDT electrodes so as to interpose the pair of IDT electrodes therebetween, the reflectors and the pair of IDT electrodes arranged along a propagation direction of a main acoustic wave; and a dielectric film covering the pair of IDT electrodes and the reflectors, the dielectric film having a first thickness over at least a portion of the reflectors, the dielectric film having a second thickness over an entirety of the pair of IDT electrodes, the first thickness being different from the second thickness.
2. 2 . The acoustic wave device of claim 1 wherein each of the reflectors includes an inner portion and an end portion, the end portion being disposed further from the pair of IDT electrodes than the inner portion, the portion of the reflectors covered by the dielectric film of the first thickness being the end portion of each reflector.
3. 3 . The acoustic wave device of claim 2 wherein the inner portion of each reflector is covered by the dielectric film of the second thickness that is thicker than the first thickness.
4. 4 . The acoustic wave device of claim 1 wherein the dielectric film of the first thickness covers an entirety of the reflectors.
5. 5 . The acoustic wave device of claim 1 wherein the respective finger of one IDT electrode is separated from an adjacent finger of the other IDT electrode by a first pitch distance, each of the reflectors including a plurality of fingers separated from each other by a second pitch distance which are extending in a same direction of extension as the respective finger of the pair of IDT electrodes.
6. 6 . The acoustic wave device of claim 5 wherein the second pitch distance is larger than the first pitch distance.
7. 7 . The acoustic wave device of claim 1 wherein the dielectric film is formed of silicon dioxide (SiO 2 ).
8. 8 . The acoustic wave device of claim 1 wherein a surface of the dielectric film has a stair shape at a transition region connecting the first thickness and the second thickness of the dielectric film.
9. 9 . The acoustic wave device of claim 1 wherein each of the reflectors includes an inner portion and an end portion, the end portion being disposed further from the pair of IDT electrodes than the inner portion, the portion of the reflectors covered by the dielectric film of the first thickness being the end portion of one of the reflectors, and the end portion of the other reflector is covered by the dielectric film of a third thickness that is different from the first thickness.
10. 10 . A radio frequency module comprising: a packaging board configured to receive a plurality of components; and an acoustic wave device implemented on the packaging board, the acoustic wave device including a substrate, a pair of IDT electrodes formed on the substrate, each of the pair of IDT electrodes including a bus bar and a plurality of fingers extending from the bus bar, a respective finger of one IDT electrode arranged interleaved with respective fingers of the other IDT electrode, reflectors formed on the substrate, one of the reflectors being adjacent to one side of the pair of IDT electrodes and another reflector being adjacent to an opposite side of the pair of IDT electrodes so as to interpose the pair of IDT electrodes therebetween, the reflectors and the pair of IDT electrodes arranged along a propagation direction of a main acoustic wave, and a dielectric film covering the pair of IDT electrodes and the reflectors, the dielectric film having a first thickness over at least a portion of the reflectors, and a second thickness over an entirety of the pair of IDT electrodes, the first thickness being different from the second thickness.
11. 11 . The radio frequency module of claim 10 wherein each of the reflectors includes an inner portion and an end portion, the end portion being disposed further from the pair of IDT electrodes than the inner portion, the portion of the reflectors covered by the dielectric film of the first thickness being the end portion of one of the reflectors, and the end portion of the other reflector is covered by the dielectric film of a third thickness that is different from the first thickness.
12. 12 . The radio frequency module of claim 10 wherein the radio frequency module is a front-end module.
13. 13 . The radio frequency module of claim 12 wherein inner portions of each reflector adjacent to the pair of IDT electrodes are covered by the dielectric film of the second thickness that is thicker than the first thickness.
14. 14 . The radio frequency module of claim 10 wherein the dielectric film of the first thickness covers an entirety of the reflectors.
15. 15 . The radio frequency module of claim 10 wherein the respective finger of one IDT electrode is separated from an adjacent finger of the other IDT electrode by a first pitch distance, each of the reflectors including a plurality of fingers separated from each other by a second pitch distance which are extending in a same direction of extension as the respective finger of the pair of IDT electrodes.
16. 16 . The radio frequency module of claim 15 wherein the second pitch distance is larger than the first pitch distance.
17. 17 . A mobile device comprising: an antenna configured to receive a radio frequency signal; and a front end system configured to communicate with the antenna, the front end system including an acoustic wave device including a substrate, a pair of IDT electrodes formed on the substrate, each of the pair of IDT electrodes including a bus bar and a plurality of fingers extending from the bus bar, a respective finger of one IDT electrode arranged interleaved with respective fingers of the other IDT electrode, reflectors formed on the substrate, one of the reflectors being adjacent to one side of the pair of IDT electrodes and another reflector being adjacent to an opposite side of the pair of IDT electrodes so as to interpose the pair of IDT electrodes therebetween, the reflectors and the pair of IDT electrodes arranged along a propagation direction of a main acoustic wave, and a dielectric film covering the pair of IDT electrodes and the reflectors, the dielectric film having a first thickness over at least a portion of the reflectors, the dielectric film having a second thickness over an entirety of the pair of IDT electrodes, the first thickness being different from the second thickness.
18. 18 . The mobile device of claim 17 wherein each of the reflectors includes an inner portion and an end portion, the end portion being disposed further from the pair of IDT electrodes than the inner portion, the portion of the reflectors covered by the dielectric film of the first thickness being the end portion of one of the reflectors, and the end portion of the other reflector is covered by the dielectric film of a third thickness that is different from the first thickness.
19. 19 . The mobile device of claim 17 wherein the respective finger of one IDT electrode is separated from an adjacent finger of the other IDT electrode by a first pitch distance, each of the reflectors including a plurality of fingers separated from each other by a second pitch distance which are extending in a same direction of extension as the respective finger of the pair of IDT electrodes, the second pitch distance being larger than the first pitch distance.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application Ser. No. 63/442,833, titled “INCREASED DIELECTRIC FILM THICKNESS REFLECTOR IN A TEMPERATURE COMPENSATED SAW RESONATOR,” Feb. 2, 2023, the entire content of which is incorporated herein by reference for all purposes. BACKGROUND Field Aspects and embodiments of the present disclosure relate to electronic systems, and in particular, to a filter for use in radio frequency (RF) electronics. Description of the Related Technology Filters are used in radio frequency (RF) communication systems to allow signals to pass through at discreet frequencies but reject any frequency outside of the specified range. An acoustic wave filter, which is used widely in the wireless communication field, can include a plurality of resonators arranged to filter a radio frequency signal. Example acoustic wave filters include surface acoustic wave (SAW) filters and/or bulk acoustic wave (BAW) filters. A film bulk acoustic resonator (FBAR) filter is an example of a BAW filter. Acoustic wave filters can be implemented in radio frequency electronic systems. For instance, filters in a radio frequency front end of a mobile phone can include acoustic wave filters. A plurality of acoustic wave filters can be arranged as a multiplexer. For example, two surface acoustic wave filters can be arranged as a duplexer. Examples of RF communication systems with one or more filter module include, but are not limited to, mobile phones, tablets, base stations, network access points, customer-premises equipment (CPE), laptops, and wearable electronics. For example, in wireless devices that communicate using a cellular standard, a wireless local area network (WLAN) standard, and/or any other suitable communication standard, a power amplifier can be used for RF signal amplification. An RF signal can have a frequency in the range of about 30 kHz to 300 GHz, such as in the range of about 410 MHz to about 7.125 GHz for certain communications standards. SUMMARY In accordance with one aspect, there is provided an acoustic wave device. The acoustic wave device comprises a substrate, a pair of IDT electrodes formed on the substrate, each of the pair of IDT electrodes including a bus bar and a plurality of fingers extending from the bus bar, a respective finger of one IDT electrode arranged interleaved with respective fingers of the other IDT electrode, reflectors formed on the substrate, one of the reflectors being adjacent to one side of the pair of IDT electrodes and another reflector being adjacent to the opposite side of the pair of IDT electrodes so as to interpose the pair of IDT electrodes therebetween, the reflectors and the pair of IDT electrodes arranged along a propagation direction of a main acoustic wave, and a dielectric film covering the pair of IDT electrodes and the reflectors, the dielectric film having a first thickness covering at least a portion of the reflectors, the dielectric film having a second thickness covering the pair of IDT electrodes, the first thickness being different from the second thickness. In some embodiments, the portion of the reflectors covered by the dielectric film of the first thickness is both end portions of each reflector remote from the pair of IDT electrodes. In some embodiments, inner portions of each reflector adjacent to the pair of IDT electrodes are covered by the dielectric film of the second thickness that is thicker than the first thickness. In some embodiments, the dielectric film of the first thickness covers an entirety of the reflectors. In some embodiments, the respective finger of one IDT electrode is separated from an adjacent finger of the other IDT electrode by a first pitch distance, each of the reflectors including a plurality of fingers separated from each other by a second pitch distance which are extending in a same direction of extension as the respective finger of the pair of IDT electrodes. In some embodiments, the second pitch distance is larger than the first pitch distance. In some embodiments, the dielectric film is formed of silicon dioxide (SiO2). In some embodiments, a surface of the dielectric film has a stair shape at a transition region connecting the first thickness and the second thickness of the dielectric film. In some embodiments, a surface of the dielectric film has a sloped shape at a transition region connecting the first thickness and the second thickness of the dielectric film. In some embodiments, the portion of the reflectors covered by the dielectric film of the first thickness is an end portion of one of the reflectors remote from the pair of IDT electrodes, and an end portion of the other reflector remote from the pair of IDT electrodes is covered by the dielectric film of a third thickness that is different from the first thickness. In accordance with another aspect, there is provided a radio frequency module. The radio frequency m