A high-reliability thin-film bulk acoustic wave resonator and its manufacturing method

Abstract

The application discloses a high-reliability FBAR (film bulk acoustic resonator), which has an isolation layer on the entire substrate, and an air cavity recessed from the upper surface of the substrate between the substrate and the isolation layer; isolation A lower electrode, a piezoelectric layer, and an upper electrode are respectively located above the layers; and a passivation layer covering at least the entire upper electrode and / or an exposed portion of the lower electrode is located above the upper electrode. Compared with the existing FBAR, the present application adds an isolation layer with the same size as the substrate on the substrate. On the one hand, this can reduce the requirements on the resistivity of the substrate material, thereby reducing the cost of the substrate; on the other hand, without changing the substrate material, the isolation between the substrate and the device can be improved, thereby improving the resonance open circuit impedance of the device. The present application also adds a passivation layer on the exposed part of the upper electrode and / or the lower electrode, which can effectively prevent the influence of the upper electrode and / or the lower electrode on the performance and long-term reliability of the device due to oxidation and other deterioration.

Description

technical field [0001] The present application relates to a thin-film bulk acoustic resonator (FBAR or TFBAR, thin-film bulk acoustic resonator). Background technique [0002] FBAR is a semiconductor device that mainly includes a piezoelectric material sandwiched between two electrodes, and the three form a sandwich structure. FBAR is often used to make radio frequency filters in wireless devices such as mobile phones. The filter is composed of a group of FBARs, such as half-ladder, full-ladder, lattice, stacked ( stack) and other topological structures, which are used to filter out unwanted frequencies while allowing specific frequencies to pass. FBAR is also used to make duplexers to partially replace early surface acoustic wave (SAW, surface acoustic wave) devices. Its advantages lie in small size, advanced technology, and improved efficiency. In addition, FBAR is also used to make microwave oscillators, sensors, power amplifiers, low noise amplifiers, etc. [0003] se...

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Problems solved by technology

Therefore, a small part of the overlapping area between the lower electrode 3 and the upper electrode 5 is not above the air cavity 2, which will cause leakage of sound waves and affect the quality factor of FBAR

[0016] Third, the upper electrode 5 is exposed in the air, which is easy to oxidize, deteriorate, etc., thereby affecting the parameters such as the frequency of the FBAR

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