CN215418219U - Surface acoustic wave filter with non-continuous substrate structure - Google Patents
Surface acoustic wave filter with non-continuous substrate structure Download PDFInfo
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- CN215418219U CN215418219U CN202120607256.4U CN202120607256U CN215418219U CN 215418219 U CN215418219 U CN 215418219U CN 202120607256 U CN202120607256 U CN 202120607256U CN 215418219 U CN215418219 U CN 215418219U
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Abstract
The utility model provides a surface acoustic wave filter with a discontinuous substrate structure, which comprises the following structures: 1) a substrate layer; 2) a piezoelectric film layer and an acoustic impedance discontinuous layer contained therein disposed on the substrate layer; 3) and the interdigital transducer is arranged on the piezoelectric film layer. By the scheme of the utility model, acoustic impedance conditions can be changed or periodic design can be carried out on a surface acoustic wave device (SAW) propagation path, and the surface acoustic wave propagation characteristics are modulated, so that the improvement of performance indexes such as quality factors (Q values), bandwidth and insertion loss of the surface acoustic wave filter is finally realized. The piezoelectric film adopted in the utility model has lower price compared with the traditional single crystal material, and the void space with discontinuous acoustic impedance can be easily prepared by adopting stripping and etching processes.
Description
Technical Field
The utility model relates to the technical field of semiconductor material and device preparation, in particular to a surface acoustic wave filter with a discontinuous substrate structure.
Background
A Surface Acoustic Wave (SAW) is an elastic wave that propagates along an elastic solid Surface or a dielectric Surface. The surface acoustic wave filter is a frequency selective device made using the piezoelectric effect and the physical characteristics of surface acoustic wave propagation. The SAW filter has the characteristics of flexible design, analog/digital compatibility, reduced in-band attenuation, good anti-electromagnetic interference (EMI) performance, small volume, light weight, high reliability and the like, and the SAW filter is widely applied to a plurality of fields such as base stations, navigation, mobile communication and the like.
The surface acoustic wave filter converts an input electric signal into an acoustic signal by a back pressure effect through the input IDT, the acoustic signal propagates along the substrate surface, reaches the output IDT along the substrate, and the acoustic signal is finally converted into an electric signal by the output IDT to be output. In order to realize the frequency selection function, most of the technologies are to design and optimize transducers, that is, interdigital transducers (IDTs), for example, by designing apertures, widths, thicknesses, numbers, and the like of fingers, and the design of surface acoustic wave propagation path structures is relatively rare, especially the propagation surfaces are designed continuously or approximately continuously, wherein a patent with publication number CN 110971210 a of north and middle university proposes a structure of a metal lattice designed between two transducers to realize a frequency-selective signal processing technology. However, the method has limited adjustable parameters, high requirements on process control and limited improvement on the performance of the filter. At present, the technology of the discontinuous structure of the surface acoustic wave filter propagation path is blank at present.
SUMMERY OF THE UTILITY MODEL
Aiming at the problems that the continuous and uniform substrate structure is adopted in the SAW (surface acoustic wave) propagation direction in the prior art disclosed at present, the utility model provides a novel substrate structure which is discontinuous in the propagation direction, namely, the acoustic impedance is mutated, and the technical scheme is adopted to realize that:
a surface acoustic wave filter with a discontinuous substrate structure comprises the following structures:
1) a substrate layer;
2) a piezoelectric thin film layer disposed on the substrate layer and an acoustic impedance discontinuity layer contained therein;
3) and the interdigital transducer is arranged on the piezoelectric film layer.
Optionally, the substrate layer is silicon, germanium, gallium arsenide, silicon carbide, sapphire, gallium nitride or aluminum nitride.
Optionally, the piezoelectric thin film layer is an AlN piezoelectric thin film, or an AlN piezoelectric thin film doped with one or more elements of Sc, Cr, and Er.
Preferably, the thickness of the AlN piezoelectric film or the doped AlN piezoelectric film is 100nm-10 um.
Optionally, the material of the acoustic impedance discontinuous layer is a low acoustic velocity material, a high acoustic velocity material, and a hollow structure.
Optionally, the region where the acoustic impedance discontinuous layer is located is a uniform structure, a gradual change structure, or a periodic change structure.
Optionally, the acoustic impedance discontinuous layer is a single-layer or multi-layer structure.
Optionally, the electrode material of the interdigital transducer is a material of an electrode layer, and includes Al, Pt, Ti, Au, Mo, or W.
Optionally, the thickness of the electrode layer is 30nm-2 um.
The utility model has the following beneficial effects:
by the scheme of the utility model, acoustic impedance conditions can be changed or periodic design can be carried out on the SAW propagation path, and the SAW propagation characteristics are modulated, so that the improvement of performance indexes such as Q value, bandwidth and insertion loss of the SAW filter is finally realized. The piezoelectric film adopted in the utility model has lower price compared with the traditional single crystal material, and the void space with discontinuous acoustic impedance can be easily prepared by adopting stripping and etching processes.
Drawings
Fig. 1 is a schematic structural diagram of a surface acoustic wave filter with a discontinuous substrate structure according to an embodiment of the present invention.
FIG. 2 is a flow chart of an etching-type manufacturing process of a surface acoustic wave filter with a discontinuous base structure according to an embodiment of the present invention.
FIG. 3 is a flow chart of a strip-type manufacturing process of a surface acoustic wave filter with a discontinuous base structure according to an embodiment of the present invention.
Detailed Description
For a further understanding of the utility model, reference will now be made to the preferred embodiments of the utility model by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the utility model, and not to limit the scope of the claims.
Example 1
As shown in fig. 1, the surface acoustic wave filter with a discontinuous substrate structure includes the following structures:
1) a substrate layer 1;
2) a piezoelectric thin film layer 2 disposed on the substrate layer and an acoustic impedance discontinuous layer 3 contained therein;
3) and an interdigital transducer 4 arranged on the piezoelectric film layer.
As an alternative embodiment, the substrate layer 1 is silicon, germanium, gallium arsenide, silicon carbide, sapphire, gallium nitride or aluminum nitride.
The piezoelectric film layer 2 is an AlN piezoelectric film or an AlN piezoelectric film doped with one or more elements of Sc, Cr and Er, and the thickness of the AlN piezoelectric film is 100nm-10 um.
The material of the acoustic impedance discontinuous layer 3 is a low sound velocity material, a high sound velocity material and a hollow structure, and the area of the acoustic impedance discontinuous layer is a uniform structure, a gradual change structure or a periodic change structure. In addition, the acoustic impedance discontinuity layer is a single layer or a multilayer structure.
The electrode material of the interdigital transducer 4 is the material of an electrode layer, and comprises Al, Pt, Ti, Au, Mo or W; the thickness of the electrode layer is 30nm-2 um.
Example 2
The preparation of the surface acoustic wave filter with a discontinuous base structure according to this embodiment will be described in detail with reference to fig. 2.
1) A substrate material 1 is prepared. In the present example, a silicon substrate was used as a substrate material, and the silicon single crystal substrate used was a produced standard specification polished substrate wafer, the surface of which was an EPI-ready polished surface subjected to RCA cleaning and had a roughness of less than 0.3nm, and the back surface of which was ground at a level of 1 ± 0.2 μm.
2) An AlN thin film 2 is grown on a substrate material 1. In this embodiment, a magnetron sputtering method (Sputter) is adopted, the pressure in the reaction chamber is 0.3pa, the flow rate of nitrogen is 160sccm, the flow rate of argon is 40sccm, the sputtering power is 4KW, the temperature is 500 ℃, and the film thickness is 2 um.
3) An Al metal electrode layer 3 is manufactured on the surface of the piezoelectric film through a plane photoetching process, so that an IDT is formed, and the thickness of the electrode layer is 1 um.
4) And preparing an acoustic impedance discontinuous layer 4 on the AlN thin film 2. And etching a hollow groove by combining a dry method or a wet method, and finally depositing a characteristic acoustic impedance material in the hollow groove to finish the preparation of the filter.
Example 3
The preparation of the surface acoustic wave filter with a discontinuous base structure according to this embodiment will be described in detail with reference to fig. 3.
1) A substrate material 1 is prepared. In the embodiment, a silicon substrate is used as a substrate material, the used silicon single crystal substrate is a produced standard specification polished substrate sheet, the surface is an EPI-ready polished surface cleaned by RCA, the roughness is less than 0.3nm, the back surface is a grinding grade, and the roughness is 1 +/-0.2 um.
2) A negative photoresist is used to fabricate a structure 2 on the silicon (or other substrate) surface that is the inverse of the design.
3) An AlN thin film 3 is grown on the substrate material 1. In this embodiment, a magnetron sputtering method (Sputter) is adopted, the pressure in the reaction chamber is 0.2pa, the flow rate of nitrogen is 140sccm, the flow rate of argon is 30sccm, the sputtering power is 3KW, the temperature is 500 ℃, and the film thickness is 4 um.
4) Forming a W metal electrode layer 4 on the AlN thin film 3 to form an IDT with an electrode layer thickness of 500nm
5) And (3) exposing the discontinuous area in a stripping mode, and filling the characteristic acoustic impedance material 5 to finish the preparation of the filter.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the utility model, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (9)
1. A surface acoustic wave filter with a discontinuous substrate structure comprises the following structures:
1) a substrate layer;
2) a piezoelectric thin film layer disposed on the substrate layer and an acoustic impedance discontinuity layer contained therein;
3) and the interdigital transducer is arranged on the piezoelectric film layer.
2. The surface acoustic wave filter of non-continuous base structure of claim 1, wherein the substrate layer is silicon, germanium, gallium arsenide, silicon carbide, sapphire, gallium nitride, or aluminum nitride.
3. The surface acoustic wave filter of a discontinuous substrate structure according to claim 1, wherein the piezoelectric thin film layer is an AlN piezoelectric thin film.
4. The surface acoustic wave filter of a discontinuous base structure according to claim 3, wherein the thickness of the AlN piezoelectric film is 100nm to 10 um.
5. The discontinuous base structure surface acoustic wave filter according to claim 1, wherein the acoustic impedance discontinuous layer is a hollow structure.
6. The surface acoustic wave filter with a discontinuous base structure according to claim 1, wherein the region where the acoustic impedance discontinuous layer is located is a uniform structure, a graded structure or a periodically varying structure.
7. The discontinuous base structure surface acoustic wave filter according to claim 1, wherein the acoustic impedance discontinuous layer is a single layer or a multilayer structure.
8. The surface acoustic wave filter with a discontinuous substrate structure according to claim 1, wherein the electrode material of the interdigital transducer is a material of an electrode layer, and comprises Al, Pt, Ti, Au, Mo or W.
9. The discontinuous base structure surface acoustic wave filter according to claim 8, wherein the thickness of the electrode layer is 30nm-2 um.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202120607256.4U CN215418219U (en) | 2021-03-25 | 2021-03-25 | Surface acoustic wave filter with non-continuous substrate structure |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202120607256.4U CN215418219U (en) | 2021-03-25 | 2021-03-25 | Surface acoustic wave filter with non-continuous substrate structure |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112968124A (en) * | 2021-03-25 | 2021-06-15 | 奥趋光电技术(杭州)有限公司 | Surface acoustic wave filter with non-continuous substrate structure and preparation method thereof |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112968124A (en) * | 2021-03-25 | 2021-06-15 | 奥趋光电技术(杭州)有限公司 | Surface acoustic wave filter with non-continuous substrate structure and preparation method thereof |
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