FBAR with temperature compensation function and resonance frequency tuning function and filter

Abstract

The invention discloses an FBAR with a temperature compensation function and a resonance frequency tuning function and a filter. The FBAR comprises a substrate, a temperature compensation and resonance frequency tuning layer, a supporting layer, a bottom electrode, a top electrode and a piezoelectric film. The middle of the bottom of the temperature compensation and resonance frequency tuning layer is provided with a groove, the substrate is arranged under the two sides of the groove, and a cavity is formed through the substrate and the bottom face of the temperature compensation and resonance frequency tuning layer; the supporting layer is arranged on the upper side of the temperature compensation and resonance frequency tuning layer; the piezoelectric film is arranged between the bottom electrode and the top electrode; the FBAR and the filter can effectively reduce temperature and frequency drift caused by a piezoelectric film with a negative temperature coefficient, and accordingly the temperature stability of the FBAR is improved. In the post-processing technology, the thickness of an FBAR lamination is adjusted by controlling etching time of the temperature compensation and resonance frequency tuning layer in the FBAR lamination, frequency drift caused by process errors can be effectively reduced, and the frequency accuracy of the FBAR is improved.

Description

technical field [0001] The invention belongs to the field of radio frequency and micro-electromechanical systems, in particular to an FBAR with functions of temperature compensation and resonant frequency trimming and a narrow bandwidth filter using the FBAR. technical background [0002] RF filters currently used in radio frequency front-end modules mainly include Surface Acoustic Wave (SAW, Surface Acoustic Wave) filters and dielectric ceramic filters. For the dielectric ceramic filter, its main disadvantage is that it is large in size and cannot be integrated in a single chip, which cannot meet the requirements of portability; for the SAW filter, its main disadvantage is that the operating frequency is low and the power capacity is small. It cannot meet the requirements of high frequency band and multi-band. Due to the continuous progress of Micro-Electro-Mechanic System (MEMS, Micro-Electro-Mechanic System) technology, the development of microfabrication technology has ...

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Problems solved by technology

In an FBAR device, due to processing deviations, the resonant frequency of the processed FBAR is usually different from the target value, then the designed FBAR device cannot meet the requirements of the design specifications

[0004] John D. Larson, III discloses a temperature-compensated FBAR device in an invention titled Temperature-compensated film bulk acoustic resonator (FBAR) devices US Patent No. 7408428B2, the cavity of the temperature-compensated FBAR device is released by a sacrificial layer process Obtained, this process is prone to the following problems: one, chemical mechanical polishing needs to be used before the release of the sacrificial layer, the process is complex, and the precision is difficult to control; two, the release of the sacrificial layer is also relatively difficult; three, the adhesive produced after the release The side effect has a very serious impact on the device

At the same time, the FBAR proposed in this patent only considers the influence of temperature-frequency drift characteristics, and does not consider the tunable resonance frequency

Another Chinese patent document with publication number CN101977026A and a publication date of February 16, 2011 discloses a method for manufacturing a cavity-type film bulk acoustic resonator (FBAR). The main disadvantages of this scheme are: 1. Through The etching window performs wet etching on the silicon material on the top layer, and it is difficult to control the thickness of the etched film layer. Therefore, it is impossible to achieve accurate resonant frequency adjustment; 2. The structure supporting the FBAR stack is only a layer of silicon material, and the device’s The mechanical strength is poor; 3. Only the trimming of the resonance frequency is considered, and the influence of temperature-frequency drift characteristics is not considered

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