A low-cost high-performance surface acoustic wave filter structure

Abstract

This invention proposes a low-cost, high-performance surface acoustic wave (SAW) filter structure, comprising a substrate, which includes a monocrystalline silicon layer, a high acoustic impedance quartz glass layer, and a piezoelectric layer stacked sequentially. The piezoelectric layer has a thickness of <1 μm, and an electrode structure is disposed on the piezoelectric layer. This SAW filter structure eliminates the need for the traditional high-resistivity silicon layer, significantly reducing the manufacturing cost of the SAW filter. High Q-value and high performance are achieved through acoustic impedance and electrical impedance matching between the high-resistivity quartz glass layer and the monocrystalline silicon layer. Furthermore, the fabrication process of this SAW filter is simple, employing conventional microelectronic processing techniques, and is easily scalable for mass production.

Description

Technical Field

[0001] This utility model relates to the field of filter technology, specifically to a low-cost, high-performance surface acoustic wave filter structure. Background Technology

[0002] With the rapid development of mobile communication technology, the significant increase in the number of communication frequency bands has placed higher demands on the performance of filters. Against this backdrop, SAW (Surface Acoustic Wave) filters have secured an important position in the mobile communication field due to their excellent performance. POI (Piezoelectric On Insulator) SAW filters, as a novel variant of SAW filters, have become a rising star in the mobile communication field due to their unique advantages and broad application prospects.

[0003] The POI SAW filter employs a multilayer substrate design, consisting of a thin layer of piezoelectric single-crystal material (such as single-crystal lithium tantalate or lithium niobate), a silicon dioxide layer, and a high-resistivity silicon substrate. This unique design significantly improves the performance of the POI SAW filter compared to traditional SAW filters, specifically in terms of high-frequency characteristics, high quality factor, low temperature sensitivity, and wide bandwidth.

[0004] High-Frequency Characteristics: POI SAW filters support higher operating frequencies, meeting the high-frequency signal processing requirements of modern mobile communication systems. High Quality Factor (Q Value): Through a carefully designed multi-layer structure, POI SAW filters achieve a high Q value, which helps reduce signal loss and improve the efficiency and accuracy of signal processing. Low Temperature Sensitivity: The multi-layer substrate design reduces the sensitivity of POI SAW filters to temperature changes, thereby improving their stability in different environments. Large Bandwidth: POI SAW filters have a large bandwidth, enabling them to process signals in multiple frequency bands simultaneously, meeting the multi-band support requirements of mobile communication systems.

[0005] With the popularization of 5G technology and the development of future mobile communication systems, the performance requirements for filters will become increasingly stringent. POI SAW filters, with their high frequency, high Q value, and large bandwidth, will become an indispensable component in future mobile communication systems, IoT devices, and automotive electronics.

[0006] However, the manufacturing cost of POI substrates is high, especially the cost of the high-resistivity silicon layer, which accounts for a significant portion of the overall cost. This limits the large-scale application of POI SAW filters. Therefore, how to reduce the manufacturing cost of POI SAW filters while maintaining their high performance has become an urgent problem to be solved in this field. Utility Model Content

[0007] In order to overcome the defects in the existing technology, the purpose of this utility model is to provide a low-cost, high-performance surface acoustic wave filter structure.

[0008] To achieve the above-mentioned objectives of this utility model, this utility model provides a low-cost, high-performance surface acoustic wave filter structure, including a substrate. The substrate includes a single-crystal silicon layer, a high acoustic impedance quartz glass layer, and a piezoelectric layer stacked sequentially. The thickness of the piezoelectric layer is <1 μm, and an electrode structure is disposed on the piezoelectric layer.

[0009] This surface acoustic wave (SAW) filter structure eliminates the need for the traditional high-resistivity silicon layer, significantly reducing manufacturing costs. High Q-value and high performance are achieved through acoustic impedance and electrical impedance matching between the quartz glass layer and the single-crystal silicon layer. Furthermore, the fabrication process for this SAW filter is simple, utilizing conventional microelectronics processing techniques, and is easily scalable for mass production.

[0010] Optionally, the piezoelectric layer is smooth on both sides.

[0011] The piezoelectric layer is less than 1 μm thick and has smooth surfaces on both sides, which improves response speed and sensitivity, reduces surface defects and lowers noise.

[0012] Optionally, the quartz glass layer is quartz glass doped with oxides.

[0013] In this alternative approach, the added oxides can enter the glass network structure, altering the chemical bond properties and structure of the glass, increasing the resistance to ion migration, and thus improving the resistivity of the quartz glass.

[0014] Optionally, the oxide is aluminum oxide and / or yttrium oxide.

[0015] Optionally, the quartz glass layer is quartz glass doped with fluoride.

[0016] In this alternative, the added fluoride can reduce the oxygen ion concentration in the glass, thus reducing the likelihood of oxygen ion conductivity; at the same time, the fluoride can also improve the structure of the glass, enhancing the chemical stability and resistivity of the quartz glass.

[0017] Optionally, the surface of the quartz glass layer in contact with the piezoelectric layer is coated with an insulating coating.

[0018] In this alternative, the insulating coating can prevent external charges and ions from contacting the glass surface, reduce surface conductivity, and increase the overall resistivity of the quartz glass layer.

[0019] Optionally, the insulating coating is silicon nitride.

[0020] Optionally, the surface of the quartz glass layer is smooth.

[0021] This alternative approach reduces surface charge accumulation and conduction by minimizing surface defects and roughness, thereby increasing the surface resistivity of the glass and ultimately improving the overall resistivity of the quartz glass layer.

[0022] Optionally, both sides of the quartz glass layer are smooth.

[0023] Optionally, the thickness of the piezoelectric layer is 500nm-800nm.

[0024] According to another preferred embodiment of the present invention, the thickness of the quartz glass layer is...

[0025] 400nm-2000nm.

[0026] According to another preferred embodiment of the present invention, the thickness of the single-crystal silicon layer is 100nm-200um.

[0027] To achieve the fabrication of a low-cost filter with high response speed and sensitivity.

[0028] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0029] The above and / or additional aspects and advantages of this utility model will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0030] Figure 1 This is a schematic cross-sectional view of the substrate structure of this utility model. Detailed Implementation

[0031] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0032] In the description of this utility model, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0033] This invention provides a low-cost, high-performance surface acoustic wave filter structure, which includes a substrate, wherein the substrate is a POI sheet, such as... Figure 1As shown, the surface acoustic wave (SAW) filter comprises a single-crystal silicon layer, a high acoustic impedance quartz glass layer, and a piezoelectric layer stacked sequentially. The piezoelectric layer has a thickness of <1 μm and is smooth on both sides. The electrode structure of the SAW filter is disposed on the piezoelectric layer. In this embodiment, the thickness of the piezoelectric layer is 500 nm-800 nm, the thickness of the quartz glass layer is 400 nm-2000 nm, and the thickness of the single-crystal silicon layer is 100 μm-200 μm. Specifically, quartz glass and single-crystal silicon are used as starting materials. After the quartz glass layer and the single-crystal silicon layer are bonded, the piezoelectric layer is formed after the quartz glass layer is bonded, forming a piezoelectric layer + quartz glass layer + single-crystal silicon layer substrate to form a POI wafer. The electrode structure is fabricated on the piezoelectric layer using microelectronic processing techniques such as photolithography, evaporation, and sputtering.

[0034] The piezoelectric layer is used to excite surface acoustic waves. The acoustic wave energy is confined within the piezoelectric layer by the acoustic impedance and electrical impedance of the quartz glass layer and the single-crystal silicon layer, thereby achieving a high Q value. In this embodiment, the piezoelectric layer can be made of commonly used piezoelectric materials, such as lithium niobate (LiNbO3) or lithium tantalate (LiTaO3).

[0035] The quartz glass layer can be made of one or any combination of the following schemes to achieve high resistivity and thus achieve the high resistivity characteristics of the quartz glass layer.

[0036] The first type is a quartz glass layer made from high-purity raw materials, such as high-purity quartz sand and / or fully dried raw materials. Using higher-purity raw materials reduces conductive impurities from the source, increasing the glass's resistivity; fully drying the raw materials removes moisture, reducing conductivity caused by moisture and further improving the glass's resistivity.

[0037] The second type is a quartz glass layer with a uniform and stable structure. In practice, the temperature can be precisely controlled to form a uniform and stable structure in the glass, reducing defects and ion migration channels, thereby improving resistivity.

[0038] The third type is a quartz glass layer with a compact, disordered structure. In practice, a rapid cooling process can be used to create a more compact, disordered structure in the glass, reducing the space for ions to move and lowering the likelihood of ionic conductivity. At the same time, rapid cooling can also suppress the precipitation and aggregation of impurities, helping to maintain the glass's high resistivity.

[0039] The fourth type is a quartz glass layer with added high-resistivity material.

[0040] For example, quartz glass layers doped with high-resistivity oxides, such as aluminum oxide (Al₂O₃) and yttrium oxide (Y₂O₃). These oxides can enter the glass network structure, altering the chemical bond properties and structure of the glass, increasing the resistance to ion migration, and thus improving the glass's resistivity.

[0041] For example, in quartz glass layers doped with fluorides, the introduction of fluorides can reduce the concentration of oxygen ions in the glass, thus decreasing the likelihood of oxygen ions conducting electricity. At the same time, fluorides can also improve the glass's structure, enhancing its chemical stability and resistivity.

[0042] Oxides and fluorides can be added simultaneously.

[0043] In a more preferred embodiment, a coating with good insulating properties, such as silicon nitride (Si3N4), is applied to the surface where the quartz glass layer and the piezoelectric layer contact. These coatings can prevent external charges and ions from contacting the glass surface, reduce surface conductivity, and improve the overall resistivity of the glass.

[0044] The fifth type is a smooth-surfaced quartz glass layer, preferably with smooth surfaces on both sides. The surface resistivity of the quartz glass layer should be around 10⁻⁶. 14 Ω-10 17 When the surface resistivity is within the Ω range, the acceptable smoothness requirement is met. This can be achieved by polishing the surface of the quartz glass layer. Polishing reduces defects and roughness on the surface of the quartz glass layer. A smooth surface can reduce the accumulation and conduction of surface charge, increase the surface resistivity of the glass, and thus increase the overall resistivity.

[0045] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0046] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A low-cost, high-performance surface acoustic wave filter structure, characterized in that, The substrate includes a single-crystal silicon layer, a high acoustic impedance quartz glass layer, and a piezoelectric layer stacked sequentially, wherein the thickness of the piezoelectric layer is <1µm, and an electrode structure is disposed on the piezoelectric layer.

2. The low-cost, high-performance surface acoustic wave filter structure according to claim 1, characterized in that, The piezoelectric layer is smooth on both sides.

3. The low-cost, high-performance surface acoustic wave filter structure according to claim 1, characterized in that, The quartz glass layer is quartz glass doped with oxides.

4. The low-cost, high-performance surface acoustic wave filter structure according to claim 3, characterized in that, The oxide is aluminum oxide and / or yttrium oxide.

5. The low-cost, high-performance surface acoustic wave filter structure according to claim 1, characterized in that, The quartz glass layer is quartz glass doped with fluoride.

6. The low-cost, high-performance surface acoustic wave filter structure according to claim 1, characterized in that, The surface of the quartz glass layer that contacts the piezoelectric layer is coated with an insulating coating.

7. The low-cost, high-performance surface acoustic wave filter structure according to claim 6, characterized in that, The insulating coating is silicon nitride.

8. The low-cost, high-performance surface acoustic wave filter structure according to claim 1, characterized in that, The surface of the quartz glass layer is smooth.

9. The low-cost, high-performance surface acoustic wave filter structure according to claim 8, characterized in that, Both sides of the quartz glass layer are smooth.

10. The low-cost, high-performance surface acoustic wave filter structure according to claim 1, characterized in that, The piezoelectric layer has a thickness of 500nm-800nm, the quartz glass layer has a thickness of 400nm-2000nm, and the single-crystal silicon layer has a thickness of 100um-200um.

Images