FBAR (film bulk acoustic resonator) substrate and preparation method thereof

Abstract

The invention discloses a FBAR (film bulk acoustic resonator) substrate and a preparation method thereof. The FBAR substrate is of a W / piezoelectric film / W / DLC / air gap / Si structure. The FBAR substrate with a W / piezoelectric film / W / DLC / air gap / Si structure has the characteristics of high frequency, high Q (quality) and good frequency stability. The FBAR substrate can be used for manufacturing filters and duplexers and the like in wireless communication systems, and also can be used for manufacturing high-performance sensors in combination with sensitive films.

Description

【Technical field】 [0001] The invention relates to the cross-technical field of thin film electronic devices and micro-electromechanical systems (MEMS), in particular to a novel thin film bulk acoustic wave resonator substrate. 【Background technique】 [0002] Film Bulk Acoustic Wave Resonator (FBAR) can be divided into silicon backside etching type, air gap type, and solid-state device type. The ideal air-gap FBAR is a sandwich structure, that is, upper electrode / piezoelectric layer / lower electrode, and an air gap is etched between the silicon surface and the lower electrode surface of the FBAR to form an air interface. The actual air-gap FBAR resonator includes upper electrode / piezoelectric layer / lower electrode / support layer, and an air gap is etched between the silicon surface and the lower surface of the support layer to form an air interface, so that the upper and lower interfaces of the FBAR substrate An air reflection layer is formed, a standing wave is formed between...

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Problems solved by technology

However, the substrate temperature required for the preparation of Si3N4 thin films is relatively high, generally 800-1000°C

However, when FBAR is integrated on the semiconductor chip, the temperature of the entire process of preparing FBAR should not exceed 400°C, otherwise the channel structure of the semiconductor chip will be destroyed, so the Si3N4 film as a support layer is not compatible with the semiconductor CMOS process in terms of preparation temperature; Si3N4 thin film Soluble in HF acid, and HF acid is often used in the cleaning process of semiconductor chip preparation, so Si3N4 film as a support layer is not compatible with semiconductor CMOS technology in the cleaning process, and only discrete thin-film bulk acoustic wave devices can be prepared

[0005] At present, thin film bulk acoustic resonators mostly use aluminum and platinum (or ruthenium) as the upper and lower electrodes. Since the piezoelectric layer AlN of the thin film bulk acoustic resonator has the best comprehensive performance index, the piezoelectric layer AlN (002) grows on the lower electrode. On the other hand, the lattice constants of aluminum, platinum, and ruthenium do not match with AlN (002), which affects the quality of AlN (002), thereby affecting the performance of thin film bulk acoustic resonators

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