Film Bulk Acoustic Resonator (FBAR) is made of silicon substrate, MEMS technology and thin film technology. It realizes image elimination, parasitic filtering and channel selection in wireless transceivers.
Film Bulk Acoustic Resonator (FBAR) acoustic wave devices have the characteristics of small size, low cost, high quality factor (Q), strong power tolerance, high frequency (up to 1-10GHz) and compatibility with IC technology. It is suitable for RF system applications working at 1-10GHz and is expected to replace traditional surface acoustic wave (SAW) devices and microwave ceramics in future wireless communication systems. Therefore, it has broad application prospects in the new generation of wireless communication systems and ultra-trace biochemical detection.
With the development of thin film and micro-nano manufacturing technology, electronic devices are rapidly developing in the direction of miniaturization, high-density multiplexing, high frequency and low power consumption. Film Bulk Acoustic Resonator (FBAR) developed in recent years uses an advanced resonance technology, which converts electrical energy into sound waves to form resonance through the inverse piezoelectric effect of piezoelectric film. This resonance technology can be used to make advanced components such as thin film frequency shaping devices.
Basic structure of Film Bulk Acoustic Resonator
1. Substrate: Usually made of materials such as silicon (Si) or quartz (Quarta), used to provide structural support and a medium for sound wave propagation
2. Bottom Electrode: A conductive film located on the substrate, usually made of metal (such as aluminum, copper, platinum, etc.) materials, used to provide an electric field to excite sound waves in the film
3. Thin Film: A thin film located on the bottom electrode, usually made of voltage materials such as LiNbO3 and AI2O3, with piezoelectric effect, can generate sound waves under the action of an electric field
4. Top Electrode: A conductive film located on the film, opposite to the bottom electrode, which resonates the sound waves in the film through the action of an electric field
5. Passivation Layer: A protective film located on the top electrode, used to protect the device structure and electrical properties
Working principle of Film Bulk Acoustic Resonator
The working principle of the film bulk acoustic resonator is based on the piezoelectric effect and resonance phenomenon. When an external electric field is applied to the upper and lower electrodes of the film, the electric field of the lower electrode will cause stress in the film, which in turn causes the piezoelectric effect of the film. This piezoelectric effect causes the film to vibrate with sound waves, which propagate in the film and are received by the upper electrode. When the frequency of the sound wave matches the resonant frequency, the sound wave forms a standing wave in the film, and the energy is transmitted to the maximum effect. Its resonant frequency is determined by the physical size and material properties of the film. Different resonant frequencies can be achieved by adjusting the size and thickness of the film. In addition, by changing the intensity and frequency of the electric field, the resonant frequency can be adjusted, thereby realizing the functions of frequency synthesis and modulation
Film Bulk Acoustic Resonator Resonator Performance
(1) Frequency stability: The frequency stability of the film bulk acoustic wave resonator is high and can provide accurate frequency output
(2) Quality factor: The high quality factor can achieve a longer resonance duration
(3) Durability: It has high durability and can work stably for a long time
(4) Temperature stability: The frequency changes little with temperature and can work in a wide temperature range
Film Bulk Acoustic Resonator Classification
According to the different resonance modes, it can be divided into two categories: Piezoelectric Oscillator and Acoustic Filter
Piezoelectric Oscillator is often used in high-frequency oscillation circuits
Acoustic Filter is used for signal frequency selection
Application of thin film bulk acoustic wave resonator
It has a wide range of applications in the fields of communication, radio, electronic equipment, etc., mainly including the following aspects
(1) Communication: commonly used in mobile phones, radio and other communication equipment for frequency stability and signal modulation
(2) Radio: used in radio equipment such as RF filters and frequency synthesizers for frequency selection and signal processing
(3) Electronic equipment: commonly used in computers, TV series and other electronic products for clock synchronization and frequency stability
(4) Sensors: can be used as pressure sensors, temperature sensors, etc.
