High-performance temperature compensation surface acoustic wave filter and manufacturing method thereof

Abstract

The invention relates to the field of electronic component preparation processes, in particular to a high-performance temperature compensation surface acoustic wave filter and a manufacturing method thereof. An interdigital transducer, wherein the interdigital transducer is located at one side of the piezoelectric substrate; the transition layer is located on the side, away from the piezoelectric substrate, of the interdigital transducer, and the transition layer covers the interdigital transducer and prevents metal elements of the interdigital transducer from diffusing outwards; the functional layer is located on the side, away from the interdigital transducer, of the transition layer, the functional layer covers an active area of a metal finger strip of the interdigital transducer to form a high-sound-velocity area, the end, away from the active area, of the metal finger strip of the interdigital transducer forms a low-sound-velocity area, and a sound velocity difference is formed between the high-sound-velocity area and the low-sound-velocity area; therefore, transverse mode clutters are suppressed; the temperature compensation layer is located on the side, away from the transition layer, of the functional layer, and the temperature compensation layer covers the functional layer and the piezoelectric substrate; lateral mode clutters in TC-SAW are suppressed, and metal diffusion is suppressed at the same time.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electronic component manufacturing process, in particular to a high-performance temperature-compensated surface acoustic wave filter and a manufacturing method thereof. BACKGROUND

[0002] Temperature-compensated surface acoustic wave filter (TC-SAW) is a high-end evolution form of surface acoustic wave (SAW) technology, which significantly improves temperature stability and high-frequency performance through material and structure innovation, and is a core component in the fields of 5G communication, Internet of Things, etc. Shear horizontal-mode spurious (SH) is one of the main factors leading to the increase of TC-SAW passband ripple and insertion loss. For the problem of suppressing the shear horizontal-mode spurious of TC-SAW, the existing patents propose a piston structure, but there are problems of great overlay difficulty and difficulty in alignment. Another patent proposes a sandwiched silicon nitride or surface silicon nitride process, which uses the high acoustic velocity of silicon nitride to form a suppression effect, but this scheme has high process complexity, and problems of silicon dioxide delamination or loss of frequency modulation function of surface silicon nitride are likely to occur.

[0003] In addition, the interdigital transducer (IDT) metal finger of the existing TC-SAW usually contains copper, which is easy to diffuse when in contact with silicon dioxide, causing deterioration of filter performance; at the same time, it is also easy to be corroded by subsequent processes, causing deterioration of finger morphology. To solve the problems of copper metal diffusion and corrosion, a tantalum / nitride tantalum film is often used in semiconductor processes to form a barrier layer to block the diffusion of copper elements and external corrosion. The plating film of nitride tantalum often uses sputtering or chemical vapor deposition process, which undoubtedly increases the process complexity in the manufacturing process of surface acoustic wave filter, and may introduce new device reliability problems. SUMMARY

[0004] The present application aims to provide a high-performance temperature-compensated surface acoustic wave filter and a manufacturing method thereof, which suppresses the shear horizontal-mode spurious in the TC-SAW device and forms protection for the interdigital transducer metal finger to suppress metal diffusion.

[0005] To achieve the above-mentioned purpose, in a first aspect, the present application provides a high-performance temperature-compensated surface acoustic wave filter, characterized in that it comprises:

[0006] a piezoelectric substrate;

[0007] an interdigital transducer located on one side of the piezoelectric substrate;

[0008] A transition layer is located on the side of the interdigital transducer away from the piezoelectric substrate, covering the interdigital transducer and blocking the outward diffusion of metal elements of the interdigital transducer;

[0009] A functional layer is located on the side of the transition layer away from the interdigital transducer, covering the active area of the interdigital transducer metal finger to form a high sound speed area, and the end of the interdigital transducer metal finger away from the active area forms a low sound speed area, the high sound speed area and the low sound speed area form a sound speed difference, thereby suppressing transverse mode noise;

[0010] A temperature compensation layer is located on the side of the functional layer away from the transition layer, covering the functional layer and the piezoelectric substrate.

[0011] In a second aspect, the application provides a manufacturing method of a high-performance temperature-compensated surface acoustic wave filter as described in the first aspect, comprising:

[0012] Generating an interdigital transducer on a piezoelectric substrate; using a PECVD device to prepare a transition layer and a functional layer on the interdigital transducer; using a magnetron sputtering device to prepare a temperature compensation layer on the functional layer.

[0013] The application has the following beneficial effects:

[0014] The SiON / SiN prepared by the application x The double-layer functional layer can suppress the transverse mode noise of the TC-SAW while forming a barrier to the metal elements such as Cu in the IDT to prevent diffusion, thereby improving the performance of the device. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The application is a high-performance temperature-compensated surface acoustic wave filter;

[0016] Figure 2 The application is a simulation comparison chart;

[0017] Wherein, 1-piezoelectric substrate, 2-interdigital transducer metal finger, 3-transition layer, 4-functional layer, 5-temperature compensation layer, 6-frequency modulation layer. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0019] Embodiment 1

[0020] AsFigure 1 As shown, the application provides a high-performance temperature-compensated surface acoustic wave filter, comprising:

[0021] a piezoelectric substrate 1;

[0022] an interdigital transducer (IDT) located on one side of the piezoelectric substrate 1;

[0023] a transition layer 3 located on the side of the interdigital transducer away from the piezoelectric substrate, the transition layer covering the interdigital transducer and blocking the outward diffusion of metal elements of the interdigital transducer;

[0024] a functional layer 4 located on the side of the transition layer 3 away from the interdigital transducer, the functional layer 4 covering the active area (i.e. the area within the IDT aperture range) of the interdigital transducer metal finger 2 to form a high acoustic velocity zone, the end of the interdigital transducer metal finger 2 away from the active area forming a low acoustic velocity zone, the high acoustic velocity zone and the low acoustic velocity zone forming an acoustic velocity difference, thereby suppressing the transverse mode spur in the device passband;

[0025] a temperature compensation layer 5 located on the side of the functional layer away from the transition layer, the temperature compensation layer covering the functional layer and the piezoelectric substrate.

[0026] In this embodiment, the material of the piezoelectric substrate can be lithium niobate or lithium tantalate; the material of the interdigital transducer preferably includes one or more of titanium, copper, chromium, and silver; and the material of the temperature compensation layer is preferably silicon dioxide (SiO2).

[0027] In this embodiment, the thickness of the temperature compensation layer is 100-4000 mm.

[0028] In this embodiment, the material of the transition layer is preferably silicon oxynitride (SiON), and the material of the functional layer is preferably silicon nitride (SiNx). The SiON dielectric film as the transition layer covers the IDT, which can block the outward diffusion of metal elements such as Cu in the IDT electrode and affect the performance of the device; at the same time, the SiON dielectric film as the transition layer between the IDT and the SiNx film can also improve the adhesion between the IDT metal and the SiNx film.

[0029] In this embodiment, the thickness of the transition layer is 5-20 nm, and the thickness of the functional layer is 10-40 nm.

[0030] Embodiment 2

[0031] The embodiment provides a manufacturing method for preparing the high-performance temperature-compensated surface acoustic wave filter of embodiment 1, comprising:

[0032] An interdigital transducer is formed on a piezoelectric substrate; a transition layer and a functional layer are prepared on the interdigital transducer by using a PECVD device; and a temperature compensation layer is prepared on the functional layer by using a magnetron sputtering device;

[0033] The transition layer is made of silicon oxynitride, and the PECVD device is used to prepare the transition layer under the conditions of a power of 100-500 W, an ammonia flow rate of 50-250 sccm, a silane flow rate of 80-200 sccm, a laughing gas flow rate of 800-1500, and a process temperature of 250-350 ℃.

[0034] The functional layer is made of silicon nitride, and the PECVD device is used to prepare the functional layer under the conditions of a power of 100-500 W, an ammonia flow rate of 50-250 sccm, a silane flow rate of 40-100 sccm, and a process temperature of 250-350 ℃.

[0035] Embodiment 3

[0036] The embodiment provides a high-performance temperature-compensated surface acoustic wave filter, which is different from the TC-SAW of embodiment 1 in that:

[0037] As shown in Figure 1 A frequency modulation layer is prepared on the side of the temperature compensation layer away from the functional layer, and the frequency modulation layer is made of silicon nitride.

[0038] When the center frequency of the device prepared in embodiment 1 deviates from the design value, the center frequency can be changed by covering the surface with a frequency modulation layer, so that the center frequency is adjusted to the design frequency, thereby realizing accurate adjustment of the center frequency.

[0039] Silicon nitride has a high sound speed, and a relatively thin film thickness can realize frequency adjustment, which is low in cost and difficulty; on the other hand, covering the surface of the device with silicon nitride can also play a certain blocking role.

[0040] The simulation comparison results of the present application and the conventional structure are shown in Figure 2 Figure 2 (a) is the simulation admittance absolute value and real part of the conventional structure, Figure 2 (b) is the simulation admittance absolute value and real part of the present application.

[0041] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "setting", "connecting", "fixing", "rotating" and the like should be understood in a broad sense, for example, can be fixedly connected, or can be detachably connected, or can be integrated; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited, the above-mentioned terms in the present application can be understood according to the specific meaning of the above-mentioned terms in the present application by the person skilled in the art according to the specific circumstances.​

[0042] While embodiments of the application have been shown and described, it is to be understood that the application is not limited to the details of the embodiments described, since numerous changes, modifications, substitutions and variations can be made thereto without departing from the spirit and scope of the application as defined by the appended claims and their equivalents.

Claims

1. A high-performance temperature-compensated surface acoustic wave filter, characterized in that, include: piezoelectric substrate; Interdigitated transducers, wherein the interdigitated transducers are located on one side of the piezoelectric substrate; A transition layer is located on the side of the interdigital transducer away from the piezoelectric substrate. The transition layer covers the interdigital transducer and prevents the metal elements of the interdigital transducer from diffusing outward. The functional layer is located on the side of the transition layer away from the interdigital transducer. The functional layer covers the active region of the interdigital transducer metal fingers to form a high-velocity region, and the end of the interdigital transducer metal fingers away from the active region forms a low-velocity region. The high-velocity region and the low-velocity region form a sound velocity difference, thereby suppressing transverse mode clutter. A temperature compensation layer is located on the side of the functional layer away from the transition layer, and the temperature compensation layer covers the functional layer and the piezoelectric substrate.

2. The high-performance temperature-compensated surface acoustic wave filter according to claim 1, characterized in that, The transition layer is made of silicon oxynitride, and the functional layer is made of silicon nitride.

3. The high-performance temperature-compensated surface acoustic wave filter according to claim 1, characterized in that, The thickness of the transition layer is 5~20nm, and the thickness of the functional layer is 10~40nm.

4. A high-performance temperature-compensated surface acoustic wave filter according to claim 1, characterized in that, Also includes: A frequency modulation layer is located on the side of the temperature compensation layer away from the functional layer.

5. A high-performance temperature-compensated surface acoustic wave filter according to claim 4, characterized in that, The frequency modulation layer is made of silicon nitride.

6. A high-performance temperature-compensated surface acoustic wave filter according to claim 1, characterized in that, The piezoelectric substrate is made of lithium niobate or lithium tantalate.

7. A method for fabricating a high-performance temperature-compensated surface acoustic wave filter, characterized in that, include: Interdigitated transducers are fabricated on piezoelectric substrates; A transition layer and a functional layer were fabricated on the interdigital transducer using PECVD equipment; a temperature compensation layer was fabricated on the functional layer using magnetron sputtering equipment.

8. The method for fabricating a high-performance temperature-compensated surface acoustic wave filter according to claim 7, characterized in that, The transition layer material is silicon oxynitride. The conditions for preparing the transition layer using PECVD equipment are: power of 100~500W, ammonia flow rate of 50~250sccm, silane flow rate of 80~200sccm, nitrous oxide flow rate of 800~1500, and process temperature of 250~350℃. The functional layer material is silicon nitride. The conditions for preparing the functional layer using PECVD equipment are: power of 100~500W, ammonia flow rate of 50~250sccm, silane flow rate of 40~100sccm, and process temperature of 250~350℃.

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