KR-102961041-B1 - RESONATORS WITH DIFFERENT MEMBRANE THICKNESSES ON THE SAME DIE

KR102961041B1KR 102961041 B1KR102961041 B1KR 102961041B1KR-102961041-B1

Abstract

An acoustic resonator is manufactured by bonding a first piezoelectric plate to a substrate and spanning the positions for the first cavity and the second cavity within the substrate. The upper surface of the first piezoelectric plate is flattened to a first thickness. A bonding layer is formed on the first piezoelectric plate and spans across the first cavity position and the second cavity position. A second piezoelectric plate is bonded to the bonding layer and spans across the first cavity position and the second cavity position. A portion of the second piezoelectric plate spanning the second cavity position is etched to form a first membrane over the first cavity position and a second membrane over the second cavity position. An interdigital transducer is formed on the first membrane and the second membrane over the first cavity position and the second cavity position to form the first resonator and the second resonator on the same die.

Inventors

터너, 패트릭
자쇼스키, 더그
가르시아, 브라이언트

Assignees

가부시키가이샤 무라타 세이사쿠쇼

Dates

Publication Date: 20260508
Application Date: 20210831
Priority Date: 20201217

Claims (15)

In a filter device, A first interdigital transducer (IDT) and a second interdigital transducer provided on a single die; A first piezoelectric plate provided below both the first interdigital transducer and the second interdigital transducer; A second piezoelectric plate provided below the first interdigital transducer but not below the second interdigital transducer; and A bonding layer provided between the first piezoelectric plate and the second piezoelectric plate. A filter device characterized by including
In a filter device, A first piezoelectric plate coupled directly to the upper surface of a substrate or through one or more intermediate layers—the first piezoelectric plate extends over at least a first cavity and a second cavity, and the first piezoelectric plate includes an upper surface and has a first thickness—; A bonding layer bonded to the upper surface of the first piezoelectric plate—the bonding layer extends over the first cavity and the second cavity—; and A second piezoelectric plate having a rear surface attached to the upper surface of the bonding layer—the second piezoelectric plate extends over the first cavity but not over the second cavity— Includes, A filter device characterized in that the second piezoelectric plate has a second thickness smaller than the first thickness of the first piezoelectric plate.
A filter device according to claim 1 or 2, characterized in that the bonding layer comprises Al₂O₃ or SiO₂ .
A filter device according to claim 1 or 2, characterized in that the bonding layer comprises aluminum oxide or silicon oxide.
A filter device according to claim 1 or 2, characterized in that the bonding layer is an etch stop for etching the second piezoelectric plate.
In paragraph 1 or 2, The second piezoelectric plate is a first material that can be etched by a first process; A filter device characterized in that the bonding layer is a second material that is substantially unaffected by the first process.
A filter device according to claim 2, wherein the first resonator has the first piezoelectric plate, the bonding layer, the second piezoelectric plate, and the first interdigital transducer on the first cavity; and the second resonator has the first piezoelectric plate, the bonding layer, and the second interdigital transducer on the second cavity.
A filter device according to claim 7, characterized in that the first resonator and the second resonator are each transversely-eXited film bulk acoustic resonators (XBAR).
In paragraph 8, A filter device characterized in that the first resonator and the second resonator are configured such that a radio frequency signal applied to the first interdigital transducer and the second interdigital transducer excites different first fundamental pre-acoustic modes and second fundamental pre-acoustic modes within the first resonator and the second resonator.
A filter device according to claim 8, characterized in that the first thickness of the first piezoelectric plate and the second thickness of the second piezoelectric plate are selected to tune the first fundamental shear acoustic mode and the second fundamental shear acoustic mode.
A filter device according to claim 1 or 2, wherein the first piezoelectric plate and the second piezoelectric plate are one or more of lithium niobate and lithium tantalate.
A filter device according to claim 1 or 2, further comprising one or more openings penetrating the first piezoelectric plate, the second piezoelectric plate, and the bonding layer.
A filter device according to claim 1, characterized in that the first piezoelectric plate and the second piezoelectric plate have different thicknesses.
A filter device according to claim 1, characterized in that the first piezoelectric plate and the second piezoelectric plate have the same thickness.
A filter device according to claim 1, further comprising a first cavity and a second cavity provided between the lower surface of the substrate and the first piezoelectric plate.

Description

Resonators with different membrane thicknesses on the same die The present disclosure relates to a radio frequency filter using an acoustic wave resonator, and specifically to a filter for use within a communication device. A radio frequency (RF) filter is a two-port device configured to pass certain frequencies and block others; "passing" means transmitting with relatively low signal loss, and "blocking" means blocking or substantially attenuating. The range of frequencies passed by the filter is referred to as the filter's "passband." The range of frequencies blocked by such a filter is referred to as the filter's "blockband." A typical radio frequency filter has at least one passband and at least one blockband. Specific requirements for the passband or blockband depend on the specific application. For example, the "passband" can be defined as a frequency range where the insertion loss is better than a fixed value, such as 1 dB, 2 dB, or 3 dB. The "blockband" can be defined as a frequency range where the filter's rejection is greater than a fixed value, such as 20 dB, 30 dB, 40 dB, or a larger value depending on the application. Radio frequency filters are used within communication systems where information is transmitted over wireless links. For example, radio frequency filters can be found in cellular base stations, mobile phones and computing devices, satellite transceivers and ground stations, Internet of Things (IoT) devices, laptop computers and tablets, fixed-point wireless links, and radio frequency front-ends of other communication systems. Radio frequency filters are also used within radar electronic information combat systems. Radio frequency filters typically require many design trade-offs to achieve an optimal balance between performance parameters such as insertion loss, rejection, isolation, power handling, linearity, size, and cost for each specific application. Specific designs, manufacturing methods, and enhancements can benefit one or more of these requirements simultaneously. Performance improvements for radio frequency filters within a wireless system can have a wide-ranging impact on system performance. Improvements to radio frequency filters can be driven to provide system performance enhancements such as larger cell sizes, longer battery life, higher data rates, greater network capacity, lower costs, enhanced security, and higher reliability. These improvements can be realized at many levels of the wireless system, both individually and in combination, for example, at the radio frequency module, radio frequency transceiver, mobile or fixed subsystem, or network level. High-performance radio frequency filters for current communication systems typically include acoustic resonators, such as surface acoustic resonators, bulk acoustic resonators, film bulk acoustic resonators, and other types of acoustic resonators. However, these conventional technologies are not suitable for use at the high frequencies and bandwidths proposed for future communication networks. The demand for wider communication channel bandwidths will inevitably lead to the use of higher frequency communication bands. Radio access technology for mobile phone networks has been standardized by the 3rd Generation Partnership Project (3GPP). Radio access technology for 5th generation mobile networks is defined by the 5G NR (New Radio) standard. The 5G NR standard defines several new communication bands. Two of these new communication bands are n77, which uses a frequency range of 3300 MHz to 4200 MHz, and n79, which uses a frequency range of 4400 MHz to 5000 MHz. For both band n77 and band n79, communication devices operating in band n77 and/or band n79 use time-division transmission, which uses the same frequency for uplink and downlink transmissions. Band-pass filters for bands n77 and n79 must be capable of handling the transmission power of the communication devices. WiFi bands at 5 GHz and 6 GHz also require high frequencies and wide bandwidths. The 5G NR standard also defines millimeter-wave communication bands with frequencies from 24.25 GHz to 40 GHz. A transversely-eXited film bulk acoustic resonator (XBAR) is an acoustic resonator structure intended for use within a microwave filter. The transversely-eXited film bulk acoustic resonator is described in patent US10,491,291, titled "Transversely Excited Film Bulk Acoustic Resonator." The transversely-eXited film bulk acoustic resonator comprises an interdigital transducer (IDT) formed on a thin floating layer or diaphragm of a single-crystal piezoelectric material. The interdigital transducer comprises a first set of parallel electrode sheets extending from a first busbar and a second set of parallel electrode sheets extending from a second busbar. The first set of parallel electrode sheets and the second set of parallel electrode sheets are sandwiched between each other. A microwave signal applied to the interdigital transducer excites a shear fundamental acoustic