Preset cavity type SOI (silicon on insulator) substrate film bulk acoustic wave filter and manufacturing method thereof

Abstract

The invention discloses a preset cavity type SOI (silicon on insulator) substrate film bulk acoustic wave filter and a manufacturing method thereof, relating to the field of electronic devices. The filter is formed by electrically cascading a plurality of film bulk acoustic wave resonators which are manufactured on a preset cavity type SOI substrate, wherein each resonator comprises a piezoelectric film, a base electrode and a top electrode; a groove is arranged on the upper surface of substrate silicon of the SOI substrate; a sealed cavity is formed by the substrate silicon having the groove and top silicon; the top silicon is transferred from a groove-free SOI substrate by using a bonding technique and has even and controllable thickness; the cascaded mode of the filter includes a balancing bridge type, a stair type and a grid type; the frequency of the filter is adjustable and can be adjusted by controlling the thickness by controlling the etching time of the top silicon above the cavity; the electrodes of the resonators are approximate to oval, which is beneficial to the enhancement of the energy trap action; and a duplexer and a multiplexer can be formed by using the filter. In the invention, the advantages of SOI material are taken, the relative technique of a sacrifice layer is unnecessary, the process is simple, and the filter and the manufacturing method thereof are suitable for batch production.

Description

technical field [0001] The invention relates to the field of microelectronic devices, in particular to a thin-film bulk acoustic wave filter. Background technique [0002] Film bulk acoustic wave filter (FBAF) is a device that uses acoustic resonance to achieve electrical frequency selection. The common structure of FBAF is composed of several film bulk acoustic resonator (FBAR) units that are electrically cascaded. The basic working principle of FBAR is: when an electrical signal is loaded on the FBAR, the piezoelectric film in the device converts the electrical signal into an acoustic signal through the inverse piezoelectric effect, and the specific acoustic structure of the device presents selectivity to acoustic signals of different frequencies , to achieve the function of frequency regulation. [0003] The rapid development of wireless communication technology (such as mobile communication, wireless sensor network) and radar technology requires more and more high-perfo...

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Problems solved by technology

The FBAF products produced by Fujitsu have the following difficulties: (1) The cavity-backed FBAR needs to be carved through the entire thickness of the silicon wafer, which has a certain impact on the structural reliability; (3) During the release process of the sacrificial layer, the surroundings of the sacrificial layer, especially the upper and lower surfaces, are all surrounded by electrodes and silicon wafers, and it takes a long time to release all the sacrificial layers. (4) The step at the edge of the sacrificial layer is not smooth enough, and the film thickness of the piezoelectric layer and its electrodes is distorted here, which will cause stress concentration and cause the fracture of the transducer, and in The steps affect the formation of uniform crystal orientation of AlN(002); (5) Its adjustable FBAF needs to add additional lattice masses, which increases the process

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