CN-122026854-A - Surface acoustic wave resonator based on quartz film and processing method

Abstract

The invention provides a quartz film-based surface acoustic wave resonator which comprises a high-resistance silicon substrate, an acoustic wave reflecting layer, a single crystal quartz film, an interdigital transducer and a reflecting grating, wherein the high-resistance silicon substrate is used for realizing mechanical support of the resonator, the acoustic wave reflecting layer is made of silicon dioxide and is used for providing a temporary support and flattening substrate for an upper single crystal quartz film, a specific acoustic structure is built, inter-layer atomic diffusion and charge migration are blocked, the single crystal quartz film is a piezoelectric waveguide layer, the interdigital transducer is used for realizing acoustic-electric energy conversion, and the reflecting grating and the interdigital transducer form a Bragg-Perot Fabry-Perot resonant cavity.

Inventors

• LIU SHA
• ZHANG SHENGKANG
• XU HUIHUI
• WANG JIANBING
• WANG CHAO
• PENG HUILI
• LI YING
• QIAO ZHIFENG
• Zhao Shengshuang

Assignees

• 北京无线电计量测试研究所

Dates

Publication Date

20260512

Application Date

20251226

Claims (10)

1. 1. A surface acoustic wave resonator based on a quartz film is characterized by comprising a high-resistance silicon substrate, an acoustic wave reflecting layer, a single crystal quartz film, an interdigital transducer and a reflecting grating, wherein, The high-resistance silicon substrate is used for realizing mechanical support of the resonator; The acoustic wave reflecting layer adopts silicon dioxide and is used for providing temporary support and flattening substrates for the upper monocrystalline quartz film, constructing a specific acoustic structure and blocking interlayer atomic diffusion and charge migration; The single crystal quartz film is a piezoelectric waveguide layer; the interdigital transducer is used for realizing acoustic-electric energy conversion; The reflective grating and the interdigital transducer form a Fabry-Perot resonant cavity.
2. 2. The resonator according to claim 1, wherein the single crystal quartz film is formed on the upper surface of silicon dioxide by wafer bonding and thinning process, and is selected from ST cut, AT cut or SC cut single crystal quartz.
3. 3. The resonator according to claim 2, characterized in that the thickness d of the single crystal quartz film is designed according to the target resonance frequency f 0 , satisfying the following formula f 0 ×d＝1.5×10 3 GHz. Mu.m.
4. 4. A resonator according to claim 3, characterized in that the reflecting grating is made of metal, the metal strips have a width λ/4, and the sound waves are reflected by acoustic impedance mismatch.
5. 5. The resonator according to claim 4, characterized in that two rows of reflective gratings are placed in parallel on both sides of the interdigital transducer IDT forming a Fabry-perot resonator.
6. 6. A method for processing a resonator based on a surface acoustic wave of a quartz film is characterized by comprising the following steps: preparing polysilicon and silicon dioxide films on a substrate by chemical vapor deposition to form an acoustic wave reflecting layer; manufacturing a quartz film on the reflecting layer through a wafer bonding and thinning process to form a piezoelectric layer; patterning the first layer of metal electrode by using a photolithography process; depositing a Ti/Al electrode on the quartz film by using an electron beam evaporation process; stripping the photoresist for the first time by using a stripping process; Patterning the second layer of metal electrode by using an overlay process; Depositing an Al electrode on the first layer of metal electrode by using an electron beam evaporation process; the photoresist is stripped a second time using a stripping process.
7. 7. The method of claim 6, wherein the Al electrode deposited on the first metal electrode layer has a thickness of 2.3 μm.
8. 8. The method of claim 7, wherein the Ti electrode is 5nm and the Al electrode is 100nm of the Ti/Al electrodes deposited on the quartz film.
9. 9. The method of claim 8, wherein the thickness of the photoresist is uniform corresponding to the thickness of the electrode in the interdigital transducer region when patterning the first metal electrode using a photolithography process.
10. 10. The method of claim 9, wherein the stripping solution is acetone for about 10 minutes when the photoresist is stripped for a first time and the stripping solution is acetone for about 5 minutes when the photoresist is stripped for a second time.

Description

Surface acoustic wave resonator based on quartz film and processing method Technical Field The invention relates to the technical field of crossing of microelectronic technology and piezoelectric devices, in particular to a quartz film-based surface acoustic wave resonator and a processing method thereof. Background The Surface Acoustic Wave (SAW) resonator is a core frequency control element for realizing electric-acoustic-electric signal conversion by utilizing the inverse piezoelectric effect and the positive piezoelectric effect of piezoelectric materials, and has become a key device in the fields of wireless communication, sensors, frequency synthesis and the like by virtue of the advantages of high working frequency (reaching GHz level), small volume, high reliability, controllable cost and the like. The traditional SAW resonator mostly uses lithium niobate (LiNbO 3) as a piezoelectric substrate, and an interdigital transducer (IDT) is directly prepared on the surface of the substrate to excite sound waves, but the technical route has the inherent defect of difficult breakthrough, and severely limits the application of the device in a high-performance scene: (1) Limited quality factor (Q value), insufficient phase noise performance The acoustic loss characteristic of the lithium niobate material is remarkable, so that the acoustic wave is easy to generate energy attenuation in the propagation process, and the Q value performance of the SAW resonator is further affected. Meanwhile, the suitability of the lithium niobate and the silicon-based semiconductor process is poor, the monolithic integration with a CMOS circuit is difficult to realize, and additionally introduced packaging parasitic parameters can further deteriorate resonance characteristics, so that the phase noise performance of an oscillator constructed based on the material is limited, and the severe requirements of high-end scenes such as 5G millimeter wave communication, high-precision navigation and the like on low phase noise cannot be met. (2) Poor temperature stability and severe frequency drift The Temperature Coefficient (TCF) of the lithium niobate (LiNbO 3) material has obvious inherent characteristics, the thermal physical property of the material leads to a resonant device based on the material, the resonant frequency is easy to generate obvious drift along with the fluctuation of the ambient temperature, and the frequency stability is seriously affected. In the prior art, a temperature compensation circuit (such as a TCXO) is often adopted for correction, but the additionally added compensation circuit can lead to the increase of the volume and the power consumption of the device, which is contrary to the development trend of miniaturization and low power consumption of electronic equipment. And the compensation accuracy is limited by circuit topology and element performance, so that the frequency drift is difficult to control within the severe requirement range of high-end precision equipment, the core requirement of the frequency drift on high-frequency stability cannot be met, and the high-end application and popularization of the device are restricted. (3) Low thermal conductivity and low power handling capacity The lithium niobate (LiNbO 3) material has poor inherent thermal conductivity characteristics, resulting in limited power handling capability. Under the high-power driving or long-time continuous working scene, the heat converted by acoustic wave energy loss in the running process of the device cannot be effectively dissipated, local temperature rise is easy to occur, resonance frequency drift can be further aggravated, potential reliability hazards such as electrode migration and piezoelectric property degradation can be possibly induced, and the working stability and the service life of the device are seriously affected. The defect directly restricts the application and popularization of the lithium niobate-based device in the scenes of high-power communication terminals, industrial control and the like which have requirements on power bearing capacity. In the prior art, the SAW device using the lithium niobate film as the substrate generally has the problems of higher acoustic loss, obvious Temperature Coefficient (TCF), poor heat conductivity and the like, and severely restricts the performance upgrading of the SAW device. Although some schemes attempt to adopt the improvement of a quartz and silicon composite structure, the defects of energy leakage and the like caused by the fact that the substrate thickness is not adaptive to high frequency, the piezoelectric performance and uniformity are insufficient, and the acoustic impedance is not matched exist, and the collaborative optimization of a high Q value and high stability is difficult to realize. Therefore, how to solve the core defects of low Q value, poor temperature stability, weak power processing capability, poor process compatibility, insufficient phase