Research Of New FBAR Architecture And Sensing Technology

In recent years, with the rapid development of intelligent hardware such as wearable devices, the demands for miniaturized, flexible and transparentelectronic components become more and more urgent. Thin film bulk acoustic resonator (FBAR) is a high frequency application of Micro Electro-Mechanical System (MEMS) devices. Compared to other frequency device, FBAR has smaller volume, higher quality factor. Filters and duplexers composed of FBAR are used in the latest iphone and other products; FBAR has the characteristics of high sensitivity, is widely used in all sorts of sensing fields such as medical, biology and physics etc.Predictably, in the new electronic products, flexible transparent FBAR will have extremely extensive application prospect.A new FBAR structure by fabricating the resonator on a polymer support layer is demonstrated which permits fabrication and integration of FBARs on arbitrary substrates.This method simplifies the process, improves the yield and shows the potential of flexible and transparent FBAR.Lots of Applications based on the new FBAR architecture are proposed in this paper. The experimental details and results obtained are summarized as follows:1?The simulation model of new FBAR structure is established.Mason model simulation is carried out using ADS software, finite element simulation analysis using Comsol software. According to theoretical analysis and the acoustic impedance of different materials, we carry out the simulation by controlling the three conditions:the basal materials, materials of support layer and support layerthickness. We find that the best support layer material of making new FBAR is polyimide (PI) and PI thickness is greater than 9 ?m.2.. We have developed a process to fabricate the new FBAR devices with different thickness of PI support layer (hereinafter we designate this type of device as PI-FBAR). We contrast the results of PI-FBAR with simulation and back-trench FBAR.Tested, resonant frequencyof PI-FBARwith 2 ?m ZnO piezoelectric layer is around 1.5 GHz, the same as the traditional structure; When PI support layer thickness is greater than 9 mm, device performances almost the same with the traditional structure3?PI-FBARs are fabricated on arbitrary substrates, including copper plate, glass and paper substrates. We carry out the comparison and theoretical analysis of resonant frequency,fr and quality factor,Q for FBARs on various substrates,demonstrating the feasibility and possibility of fabricating flexible and transparent FBARs.4?Finally, some applications based on PI-FBAR such as temperature sensing, the temperature coefficient of frequency (TCF) is-45.47 ppm/k,-63.37 ppm/k and -54.56 ppm/k for FBARs on paper,copper and Si substrates respectively. We proposed a new kind of magnectic sensor based on PI-FBAR with nickel electrode. A new Ultraviolet sensor based on PI-FBAR is studied.We also fabricated PI-FBARs on silicon wafer with uneven surface, demonstrating the feasibility of fabricating FBARs on CMOS derectly. All these applications have brilliant market prospect.