Ladder-type narrow-band piezoelectric film bulk acoustic wave filter based on TSVTechnical Field
The invention belongs to the technical field of filters, and relates to a stepped narrow-band piezoelectric film bulk acoustic wave filter based on TSV.
Background
With the development of wireless communication technology, a filter in a radio frequency chip has become one of the fastest and most indispensable modules, and a thin film bulk acoustic resonator (Thin Film Bulk Acoustic Resonator, FBAR) can be applied to a high-frequency band and an infinite communication radio frequency front end required by a multi-system communication technology because of excellent performance and good compatibility, so that the filter is the optimal solution in the expansion direction of the high-frequency filter in the mobile communication field at present.
The FBAR is a device for realizing the frequency selection of the same electric signal through the resonance of an acoustic signal, the working area is composed of a metal upper electrode, a piezoelectric film and a metal lower electrode, the structure, the working mode and the material selection of the FBAR determine the characteristics that the volume is small, the propagation speed (about 331.5 m/s) of bulk acoustic waves is only 1/100000 times of the propagation speed (about 3.0 x 10 x 8 m/s) of electromagnetic waves, and therefore the volume of the working device based on the bulk acoustic wave mode is far smaller than that of the working device in the electromagnetic wave mode and the piezoelectric film material has the characteristic of high Q value, so that the resonator also has excellent characteristics, good compatibility of the processing technology and high yield. Common FBAR filter structures are typically ladder-type structures and bridge-type structures. The structure adopts an FBAR ladder-type structure.
TSV (through silicon Via) technology is used as an important component of a three-dimensional integrated circuit, TSVs in a 3D-IC are used as 'bridges' for intercommunication among layers, information exchange and transmission among different layers are realized, connection among chips is carried out through metal wires in a planar integrated circuit, and stacking among all different chips and systems can be realized in vertical interconnection. The method can obviously improve transmission efficiency, reduce power consumption and save cost, so that the design of the integrated circuit is not limited by a two-dimensional plane any more, has more degrees of freedom, has good reliability in the aspects of mechanical strength, thermal stress, heat dissipation and the like, and is one of the best solutions for solving the size limit of the two-dimensional integrated circuit at present.
Disclosure of Invention
The invention aims to provide a TSV-based ladder-type narrow-band piezoelectric film bulk acoustic wave filter, which can effectively reduce the size of the filter and improve the performance of the filter.
The technical scheme adopted by the invention is that the TSV-based ladder-type narrow-band piezoelectric film bulk acoustic wave filter comprises a silicon substrate, wherein a silicon dioxide supporting layer is arranged on the silicon substrate, and a plurality of piezoelectric film bulk acoustic wave resonators are distributed above the silicon dioxide supporting layer.
The invention is also characterized in that:
The number of the piezoelectric film bulk acoustic wave resonators is 12, the 12 piezoelectric film bulk acoustic wave resonators are respectively resonator A, resonator B, resonator C, resonator D, resonator E, resonator F, resonator G, resonator H, resonator I, resonator J, resonator K and resonator L, the resonator A, the resonator B, the resonator C, the resonator D, the resonator E and the resonator F are sequentially connected in series, the resonator G is connected with the resonator A in parallel, the resonator H is connected with the resonator B in parallel, the resonator I is connected with the resonator C in parallel, the resonator J is connected with the resonator D in parallel, the resonator K is connected with the resonator E in parallel, and the resonator L is connected with the resonator F in parallel.
The 12 piezoelectric film bulk acoustic resonators have the same structure, and the single resonator has the structure that the four TSV cylinders are uniformly distributed around the piezoelectric film of the resonator, the tops of the four TSV cylinders are connected together through pentagonal prism-shaped top electrodes, the bottoms of the four TSV cylinders are connected together through quadrilateral bottom electrodes, a silicon dioxide supporting layer is arranged between the bottom electrodes and the piezoelectric film, and a silicon dioxide isolating layer is arranged between each TSV copper cylinder and the piezoelectric film.
The top electrode and the bottom electrode are both made of copper.
AlN is selected as the material of the piezoelectric film.
The invention has the beneficial effects that the structure is a ladder-shaped filter design structure, the positions among resonators can be flexibly adjusted due to the characteristics of serial-parallel arrangement design, the area of the filter is reduced, the integration level is possessed, and the independence of the filter is improved. Compared with a common ladder-type filter, the filter has the advantages that the space can be more reasonably utilized in a limited space, the bandwidth of the filter is greatly improved, out-of-band rejection can be effectively improved, the insertion loss is less than 2dB, the return loss is less than 20dB, the design is compact, the structure is simple, and the filter can be widely applied to wireless communication systems.
Drawings
FIG. 1 is a schematic diagram of a TSV-based stepped narrowband piezoelectric film bulk acoustic filter of the present invention;
FIG. 2 is a plan view of a TSV-based stepped narrowband piezoelectric film bulk acoustic filter of the present invention;
FIG. 3 is a cross-sectional view of a TSV-based stepped narrowband piezoelectric thin film bulk acoustic filter of the present invention;
FIG. 4 is a side view of a TSV-based stepped narrowband piezoelectric film bulk acoustic resonator of the present invention;
FIG. 5 is a plan view of a TSV cylinder in a TSV-based stepped narrowband piezoelectric film bulk acoustic filter of the present invention;
Fig. 6 is an S-parameter simulation graph of a resonator in the TSV-based ladder-type narrow-band piezoelectric thin film bulk acoustic filter.
In the figure, 1. Input port, 2. Output port, 3.GND,4.TSV cylinder, 5. Top electrode, 6. Piezoelectric film, 7. Silica support layer, 8. Bottom electrode, 9. Resonator A,10. Resonator B,11. Resonator C,12. Resonator D,13. Resonator E,14. Resonator F,15. Resonator G,16. Resonator H,17. Resonator I,18. Resonator J,19. Resonator K,20. Resonator L,21. Silicon substrate, 22. Air cavity, 23. Silica isolation layer.
Detailed Description
The invention will be described in detail below with reference to the drawings and the detailed description.
The schematic diagram of the TSV-based ladder-type narrow-band piezoelectric film bulk acoustic wave filter is shown in fig. 1, and the filter is composed of 12 piezoelectric film bulk acoustic wave resonators in series-parallel connection (hereinafter, the resonators refer to the piezoelectric film bulk acoustic wave resonators);
The 12 piezoelectric film bulk acoustic resonators are respectively a resonator A9, a resonator B10, a resonator C11, a resonator D12, a resonator E13, a resonator F14, a resonator G15, a resonator H16, a resonator I17, a resonator J18, a resonator K19 and a resonator L20;
Resonator A9, resonator B10, resonator C11, resonator D12, resonator E13, and resonator F14 are sequentially connected in series, resonator G15 is connected in parallel with resonator A9, resonator H16 is connected in parallel with resonator B10, resonator I17 is connected in parallel with resonator C11, resonator J18 is connected in parallel with resonator D12, resonator K19 is connected in parallel with resonator E13, and resonator L20 is connected in parallel with resonator F14.
The resonator A9, the resonator B10, the resonator C11, the resonator D12, the resonator E13, the resonator F14, the resonator G15, the resonator H16, the resonator I17, the resonator J18, the resonator K19 and the resonator L20 are identical in structure, four TSV cylinders 4 are uniformly distributed around the resonator piezoelectric film 6 and comprise the resonator piezoelectric film 6 as shown in figures 3-5, the tops of the four TSV cylinders 4 are connected together through a pentagonal prism-shaped top electrode 5, the bottoms of the four TSV cylinders 4 are connected together through a quadrangular bottom electrode 8, a silicon dioxide supporting layer 7 is arranged between the bottom electrode 8 and the piezoelectric film 6, and a silicon dioxide isolating layer 23 is arranged between each TSV copper cylinder 4 and the piezoelectric film 6.
The top electrode 5 on the resonator A9 is connected with the input port 1, the top electrode on the resonator F14 is connected with the output port 2, and the top electrodes 5 on the resonators G15, H16, I17, J18, K19 and L20 are connected with GND3;
Each TSV copper column 4 penetrates through the piezoelectric film 6 to connect the top electrode 5 and the bottom electrode 8, wherein the top electrode 5, the bottom electrode 8, GND3 and connecting wires for connecting the top electrodes 5 in 12 resonators are all made of copper, the thickness of the copper is 0.375um, and the line width is 50um;
AlN is selected as a material of the piezoelectric film 6, and the thickness is 0.82um;
The thickness of the air cavity 22 was 1.5um, and the size of the silica support layer 7 was 600×740um2 um and the thickness was 0.15um.
In each resonator, the shape of the top electrode 5 is a regular pentagonal prism, and the radius of the top electrode circumscribed circle in the resonator A9, the resonator B10, the resonator D12, the resonator E13 and the resonator L20 is 32um;
The radius of the circumcircle of the top electrode 5 in the resonator C11 and the resonator I17 is 39um;
the radius of the top electrode circumscribing circle in the resonator F14 and the resonator IJ18 is 51um, and the radius of the top electrode 5 circumscribing circle in the resonator F14, the resonator G15 and the resonator J18 is 51um;
The radius of the circumcircle of the top electrode 5 in the resonator H16 and the resonator K19 is 71um;
The sizes of the piezoelectric film 6 and the air cavity 22 in the resonator A9, the resonator B10, the resonator C11, the resonator E13 and the resonator L20 are 90 x 90um2;
the average size of the piezoelectric film 6 and the air cavity 22 in the resonator F14, the resonator I17 is 120×100um2, and the average size of the piezoelectric film 6 and the air cavity 22 in the resonator G15, the resonator H16, the resonator J18, the resonator L20 is 150×150um2.
The insertion loss and return loss parameters of a single resonator in the TSV-based ladder-type narrow-band piezoelectric film bulk acoustic wave are shown in fig. 6, the insertion loss S12 is smaller than 2dB, and the return loss S11 is close to 20dB.