Temperature-compensated surface acoustic wave filter

Abstract

This utility model relates to the field of surface acoustic wave (SAW) filter technology, and particularly to a temperature-compensated SAW filter, comprising a wafer, a first mass load structure disposed on the wafer, an interdigital transducer disposed on the wafer and covering the first mass load structure, a first temperature compensation layer disposed on the wafer and covering the interdigital transducer, a second mass load structure disposed on the first temperature compensation layer, and a second temperature compensation layer disposed on the first temperature compensation layer and covering the second mass load structure; the first mass load structure is disposed in the finger strip region of the interdigital transducer; this utility model provides a temperature-compensated SAW filter with a simple structural design, avoids corrosion of the interdigital transducer during the operation of the mass load structure, and facilitates the suppression of clutter by the mass load structure.

Description

Technical Field

[0001] This utility model relates to the field of surface acoustic wave filter technology, and in particular to a temperature-compensated surface acoustic wave filter. Background Technology

[0002] Surface acoustic wave (SAW) filters are commonly used in communications, radar, electronic warfare, and aerospace telemetry, and are a very common and important electronic device. Temperature-compensated SAW filters (TC-SAW), a subtype of SAW filter, have a special temperature compensation layer structure that makes their frequency resistance to temperature drift approach zero, resulting in significantly improved temperature characteristics compared to conventional SAW filters. Figure 3 As shown, the temperature-compensated surface acoustic wave (SAW) filter mainly consists of an interdigital transducer (IDT), a mass load structure (PST), and a temperature compensation layer (TC). The manufacturing process is as follows: First, a patterned interdigital transducer layer is fabricated on the upper surface of the wafer. Then, a mass load structure is fabricated on the fingers of the interdigital transducer. Next, a temperature compensation layer is fabricated. Then, the surface of the temperature compensation layer is planarized. Finally, the temperature compensation layer, pad layer, passivation layer (PSV), and frequency modulation are performed. Notably, both the mass load structure and the temperature compensation layer are single layers.

[0003] Currently, the interdigital transducer fingers in existing temperature-compensated surface acoustic wave (SAW) filters are relatively narrow, making them highly susceptible to corrosion from developers, photoresists, and stripping solutions during mass-loaded operation. This results in poor product consistency and, in severe cases, significant structural defects in the interdigital transducer fingers, leading to performance degradation, failure to meet design requirements, and consequently, reduced product yield and cost control. Furthermore, parasitic capacitance in existing temperature-compensated SAW filters introduces noise, further impacting yield. Utility Model Content

[0004] The technical problem to be solved by this utility model is to overcome the shortcomings of the prior art and provide a temperature-compensated surface acoustic wave filter with a simple structural design that avoids corrosion of the interdigital transducers during the operation of the mass load structure and is conducive to the suppression of clutter in the mass load structure.

[0005] The technical solution adopted by this utility model to solve its technical problem is: a temperature-compensated surface acoustic wave filter, including a wafer, a first mass load structure disposed on the wafer, an interdigital transducer disposed on the wafer and covering the first mass load structure, a first temperature compensation layer disposed on the wafer and covering the interdigital transducer, a second mass load structure disposed on the first temperature compensation layer, and a second temperature compensation layer disposed on the first temperature compensation layer and covering the second mass load structure; the first mass load structure is disposed in the finger strip area of ​​the interdigital transducer.

[0006] Furthermore, the width of the finger strip region of the interdigital transducer is greater than the width of the first mass load structure.

[0007] Furthermore, the thickness of the first temperature compensation layer is greater than the sum of the thicknesses of the first mass load structure and the interdigital transducer.

[0008] Furthermore, the width of the second mass load structure is greater than the width of the interdigital transducer finger strip region.

[0009] Furthermore, the ratio of the width of the second mass load structure to the width of the interdigital transducer finger strip region is between 1 and 1.3.

[0010] Furthermore, the thickness of the second temperature compensation layer is greater than the thickness of the second mass load structure.

[0011] Furthermore, the thickness of the interdigital transducer is greater than the sum of the thicknesses of the first mass load structure and the second mass load structure.

[0012] The beneficial effects of this utility model are:

[0013] (1) This utility model covers the first mass load structure with an interdigital transducer and the first temperature compensation layer covers the interdigital transducer, which avoids the interdigital transducer being exposed to corrosion during the operation of the mass load structure, and prevents structural damage, improves product consistency, ensures product yield, and is conducive to cost control in product production.

[0014] (2) The present invention divides the mass load structure into two layers. The width of the first mass load structure is smaller than the width of the interdigital transducer finger strip area, which provides sufficient offset space in actual operation, making it difficult for the first mass load structure to deviate from the finger strip area of ​​the interdigital transducer. At the same time, the second mass load structure is set between the first temperature compensation layer and the second temperature compensation layer, and the width of the second mass load structure is larger than the width of the interdigital transducer finger strip area. Even if there is a deviation, compared with the prior art, the area of ​​the mass load structure overlapping directly above the interdigital transducer finger strip area is larger, which is more conducive to realizing the function of mass load structure to suppress clutter. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0016] Figure 1 This is a cross-sectional view of Embodiment 1 of this utility model;

[0017] Figure 2 This is a cross-sectional view of Embodiment 2 of this utility model;

[0018] Figure 3 This is a cross-sectional view of the prior art;

[0019] Figure 4 It is the admittance-frequency diagram used in existing technology testing;

[0020] Figure 5 This is the admittance-frequency diagram during the testing of this utility model.

[0021] In the figure: 100, wafer; 200, first mass load structure; 300, interdigitated transducer; 400, first temperature compensation layer; 500, second mass load structure; 600, second temperature compensation layer. Detailed Implementation

[0022] The present invention will now be further described with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the present invention, and therefore only show the components relevant to the present invention.

[0023] Example 1

[0024] like Figure 1 As shown, a temperature-compensated surface acoustic wave (SAW) filter includes a wafer 100, a first mass load structure 200 disposed on the wafer 100, an interdigital transducer 300 disposed on the wafer 100 and covering the first mass load structure 200, a first temperature compensation layer 400 disposed on the wafer 100 and covering the interdigital transducer 300, a second mass load structure 500 disposed on the first temperature compensation layer 400, and a second temperature compensation layer 600 disposed on the first temperature compensation layer 400 and covering the second mass load structure 500; the first mass load structure 200 is disposed in the finger region of the interdigital transducer 300. Specifically, the material of the temperature compensation layer is selected from SiO2, SiO2-SiNx, etc.; the thickness of the second temperature compensation layer 600 is greater than the thickness of the second mass load structure 500; the thickness of the interdigital transducer 300 is greater than the sum of the thicknesses of the first mass load structure 200 and the second mass load structure 500.

[0025] By covering the first mass load structure 200 with the interdigital transducer 300 (i.e., making the first mass load structure 200 first), and at the same time covering the interdigital transducer 300 with the first temperature compensation layer 400, the interdigital transducer 300 is prevented from being exposed to corrosion during the operation of the mass load structure, thus preventing structural damage, improving product consistency, ensuring product yield, and facilitating cost control in product production.

[0026] The width of the finger strip region of the interdigital transducer 300 is greater than the width of the first mass load structure 200. The width of the second mass load structure 500 is greater than the width of the finger strip region of the interdigital transducer 300. Specifically, the width of the first mass load structure 200 is generally 10-150 nm smaller than the width of the finger strip region of the interdigital transducer 300, so that the finger strip region of the interdigital transducer 300 fully covers the first mass load structure 200; the ratio of the width of the second mass load structure 500 to the width of the finger strip region of the interdigital transducer 300 is between 1 and 1.3.

[0027] The mass load structure is divided into two layers. The width of the first mass load structure 200 is smaller than the width of the finger strip area of ​​the interdigital transducer 300, providing sufficient offset space during actual operation and preventing the first mass load structure 200 from deviating from the finger strip area of ​​the interdigital transducer 300. Simultaneously, the second mass load structure 500 is positioned between the first temperature compensation layer 400 and the second temperature compensation layer 600, and its width is greater than the width of the finger strip area of ​​the interdigital transducer 300. Even if offset occurs, compared to existing technologies, the area of ​​the mass load structure overlapping directly above the finger strip area of ​​the interdigital transducer 300 is larger, which is more conducive to achieving the clutter suppression function of the mass load structure, with a suppression effect as... Figure 4 and Figure 5 As shown, black represents the absolute value curve of admittance, and gray represents the real part curve of admittance.

[0028] The thickness of the first temperature compensation layer 400 is greater than the sum of the thicknesses of the first mass load structure 200 and the interdigital transducer 300, so that the interdigital transducer 300 is completely protected under the first temperature compensation layer 400, ensuring that the interdigital transducer 300 will not be corroded or damaged during the subsequent operation of the second mass load structure 500.

[0029] It should be noted that the sum of the thicknesses of the first mass load structure 200 and the second mass load structure 500 in this application is equivalent to the thickness of the mass load structure in the prior art; the sum of the thicknesses of the first temperature compensation layer 400 and the second temperature compensation layer 600 is equivalent to the thickness of the temperature compensation layer in the prior art.

[0030] Example 2

[0031] like Figure 2As shown, the main difference between this embodiment and Embodiment 1 is that the first mass load structure 200 is omitted, and the thickness of the first mass load structure 200 is added to the thickness of the second mass load structure 500. This design eliminates the step of making the first mass load structure 200, shortening the product manufacturing process.

[0032] The above embodiments are only for illustrating the technical concept and features of this utility model. Their purpose is to enable those skilled in the art to understand the content of this utility model and implement it. They should not be used to limit the protection scope of this utility model. All equivalent changes or modifications made in accordance with the spirit and essence of this utility model should be covered within the protection scope of this utility model.

Claims

1. A temperature-compensated surface acoustic wave filter, characterized in that: The device includes a wafer (100), a first mass load structure (200) disposed on the wafer (100), an interdigital transducer (300) disposed on the wafer (100) and covering the first mass load structure (200), a first temperature compensation layer (400) disposed on the wafer (100) and covering the interdigital transducer (300), a second mass load structure (500) disposed on the first temperature compensation layer (400), and a second temperature compensation layer (600) disposed on the first temperature compensation layer (400) and covering the second mass load structure (500); the first mass load structure (200) is disposed in the finger strip area of ​​the interdigital transducer (300).

2. The temperature-compensated surface acoustic wave filter according to claim 1, characterized in that: The width of the finger strip region of the interdigital transducer (300) is greater than the width of the first mass load structure (200).

3. The temperature-compensated surface acoustic wave filter according to claim 1, characterized in that: The thickness of the first temperature compensation layer (400) is greater than the sum of the thicknesses of the first mass load structure (200) and the interdigital transducer (300).

4. The temperature-compensated surface acoustic wave filter according to claim 1, characterized in that: The width of the second mass load structure (500) is greater than the width of the finger strip area of ​​the interdigital transducer (300).

5. The temperature-compensated surface acoustic wave filter according to claim 4, characterized in that: The ratio of the width of the second mass load structure (500) to the width of the finger strip region of the interdigital transducer (300) is between 1 and 1.

3.

6. The temperature-compensated surface acoustic wave filter according to claim 1, characterized in that: The thickness of the second temperature compensation layer (600) is greater than the thickness of the second mass load structure (500).

7. The temperature-compensated surface acoustic wave filter according to claim 1, characterized in that: The thickness of the interdigital transducer (300) is greater than the sum of the thicknesses of the first mass load structure (200) and the second mass load structure (500).

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