CN-115085689-B - Air gap type FBAR

Abstract

An air-gap type Film Bulk Acoustic Resonator (FBAR) according to the present invention may include a substrate including an air gap portion on an upper surface thereof, a lower electrode formed on the substrate, a piezoelectric layer formed on the lower electrode, an upper electrode formed on the piezoelectric layer, a protective layer formed on the upper electrode, and a beam structure extending in an arch shape from one side of the upper electrode to define a space portion between the upper electrode and the piezoelectric layer, wherein one end of the beam structure is in contact with the piezoelectric layer.

Inventors

• JIN BINGXIAN
• Gao Yongxun

Assignees

• 天津威盛电子有限公司
• 天津威盛电子有限公司

Dates

Publication Date

20260421

Application Date

20210615

Priority Date

20210310

Claims (10)

1. 1. An air gap type film bulk acoustic resonator FBAR, comprising: a substrate having an air gap portion on an upper surface thereof; a lower electrode formed on the substrate; A piezoelectric layer formed on the lower electrode; an upper electrode formed on the piezoelectric layer; a protective layer formed on the upper electrode, and A beam structure on which the protective layer is formed and which extends in an arch shape from one side of the upper electrode to define a space portion between the upper electrode and the piezoelectric layer, Wherein one end of the beam structure is in contact with the piezoelectric layer, Wherein the end of the protective layer exceeds the end of the beam structure by a predetermined length.
2. 2. The air-gap FBAR of claim 1, wherein the beam structure is formed above the air gap portion with respect to a vertical virtual surface extending from a gap edge of the air gap portion.
3. 3. The air-gap FBAR of claim 1, wherein the space is filled with one of air and SiO 2 , and the density of the filled air or SiO 2 is lower than that of a material constituting the upper electrode or the piezoelectric layer.
4. 4. The air-gap FBAR of claim 1, wherein the width of the end of the beam structure in contact with the piezoelectric layer is 50 nm to 200 nm.
5. 5. The air-gap FBAR of claim 4, wherein the height of the space is less than 1/2 of the thickness of the upper electrode, and the length of the horizontal width of the space is 1 μm to 5 μm.
6. 6. The air-gap FBAR of claim 1, further comprising a conductive metal pattern layer deposited at a predetermined distance from the one end of the beam structure.
7. 7. The air-gap FBAR of claim 1, wherein a structural groove is formed on a lower surface of the beam structure, the lower surface of the beam structure corresponding to an upper portion of the space portion.
8. 8. The air-gap FBAR of claim 1, wherein a piezoelectric groove is formed on an upper surface of the piezoelectric layer, the upper surface of the piezoelectric layer corresponding to a lower portion of the space portion.
9. 9. The air-gap FBAR of claim 1, wherein a lower portion of the space comprises an inclined portion of an upper surface of the piezoelectric layer.
10. 10. The air-gap FBAR of claim 9, wherein a lower electrode edge corresponding to one end of the lower electrode is located within an upper surface of the air gap portion.

Description

Air gap type FBAR Cross Reference to Related Applications The present application claims the benefits specified by 35 USC ≡119 (a) of korean patent application No.10-2021-0031326, filed on 3 months 10 of 2021, the entire disclosure of which is incorporated herein by reference for all purposes. Technical Field The following description relates to film bulk acoustic resonators (film bulk acoustic resonator, FBARs) used in filters and diplexers for communication in the Radio Frequency (RF) band, and more particularly to air gap FBARs. Background Mobile communication technology requires a variety of Radio Frequency (RF) components that can efficiently transmit information within a limited frequency bandwidth. In particular, the filter of the RF part is one of key elements in the mobile communication technology. The filter is used to filter innumerable waves in the air to allow a user to select or transmit a desired signal, thereby achieving high quality communication. Currently, wireless communication RF filters are typically dielectric filters or surface acoustic wave (surface acoustic wave, SAW) filters. Dielectric filters provide high dielectric constant, low insertion loss, high temperature stability, and robustness to vibration and shock. However, the dielectric filter has limitations in miniaturization and application to Monolithic Microwave Integrated Circuits (MMICs), which is a trend of technical development in recent years. On the other hand, SAW filters provide small size, facilitate signal processing, have simplified circuitry, and can be mass-produced using semiconductor processes. Further, SAW filters provide high-side rejection in the passband compared to dielectric filters, enabling them to transmit and receive high quality information. However, the use of conventional interdigital transducers (INTERDIGITAL TRANSDUCERS, IDTs) for SAW filters limits the linewidth thereof, as the process for producing such SAW filters involves exposure to Ultraviolet (UV) light. Currently, the line width of such SAW filters is limited to about 0.5 μm. Thus, SAW filters cannot cover high frequency bands, for example, exceeding 5 GHz. In addition, it is still difficult to integrate SAW filters having MMIC structures on a semiconductor substrate as a single chip. In order to overcome the above limitations and problems, a Film Bulk Acoustic Resonator (FBAR) filter has been proposed in which a frequency control circuit can be integrated on an existing Si or GaAs semiconductor substrate completely in the form of an MMIC together with other active devices. FBARs are low cost, small size thin film devices that can be designed to have a high Q factor. Accordingly, the FBAR filter may be used for wireless communication devices of various frequency bands ranging from 900MHz to 10GHz, for example, and for military radars. FBARs can be an order of magnitude smaller than dielectric filters or lumped constant (lumped constant, LC) filters and have very low insertion loss compared to SAW filters. FBARs can be integrated with MMICs while providing filters with high stability and high Q-factors. For MMICs requiring high stability and high Q factor, FBARs may be the most suitable element. The FBAR filter comprises a piezoelectric dielectric material such as ZnO, AIN, or any suitable material having a high acoustic velocity. The piezoelectric material may be deposited directly onto the Si or GaAs semiconductor substrate, for example by RF sputtering. The resonance of the FBAR filter results from the piezoelectric characteristics of the piezoelectric material used therein. More specifically, the FBAR filter includes a piezoelectric film disposed between two electrodes, and generates a bulk acoustic wave to induce resonance. Various studies have been made on the FBAR structure so far. In the case of a film-type FBAR, a silicon oxide film (SiO 2) is deposited on a substrate, and a film layer is formed on the opposite side of the substrate through a cavity formed by isotropic etching. Next, a lower electrode is formed on the upper portion of the silicon oxide film, a piezoelectric material is deposited on the upper portion of the lower electrode by an RF magnetron sputtering method to form a piezoelectric layer, and an upper electrode is formed on the upper portion of the piezoelectric layer. Because of the cavity, the film FBAR provides low substrate dielectric loss and less power loss. However, the film FBAR occupies a large area due to the orientation of the silicon substrate and is easily damaged due to lower structural stability in the subsequent packaging process, resulting in lower yield. Therefore, recently, air gap and Bragg reflector type (Bragg reflector-type) FBARs have been constructed to reduce loss caused by the film and simplify the device manufacturing process. The bragg reflector type FBAR is formed by vapor deposition in the order of the reflective layer, the lower electrode, the piezoelectric layer, and the upper elec