High-performance surface acoustic wave filter and forming method thereof

Abstract

The invention discloses a high-performance surface acoustic wave filter and a forming method thereof.The filter formed through the method comprises a substrate layer, a piezoelectric layer and a resonator metal layer, the upper surface of an electrode connecting area in the resonator metal layer is further covered with a covering metal layer, and a channel cavity is formed in the portion, below the resonator metal layer, of the substrate layer; the range of the channel cavity covers the interdigital transducer. The forming method comprises the following steps: S1, providing a substrate layer and forming a channel cavity; s2, filling the channel cavity with a sacrificial layer; s3, forming an upper heat-conducting metal layer on the sacrificial layer; s4, deriving a sacrificial layer; s5, forming a piezoelectric layer; and S6, generating a resonator metal layer and a covering metal layer. The surface acoustic wave filter formed by the forming method can obstruct the transmission of body waves and improve the tolerance power at the same time.

Description

Technical Field

[0001] The invention relates to a high-performance surface acoustic wave filter and a molding method thereof, belonging to the technical field of surface acoustic wave filters. Background Art

[0002] In recent years, with the rapid development of mobile communication technology, the number of surface acoustic wave filters (Surface Acoustic Wave) required in electronic products such as mobile phones and base stations has also increased rapidly, which has put forward new requirements and challenges for the performance of SAW filters. At present, the power tolerance and insertion loss of SAW filters are still insufficient, mainly due to the relatively small size of the filter, its insufficient heat dissipation performance, and the energy leakage to the substrate due to body waves. Summary of the invention

[0003] The first technical problem to be solved by the present invention is to provide a high-performance surface acoustic wave filter, which can block the transmission of bulk waves and improve the withstand power.

[0004] The second technical problem to be solved by the present invention is to provide a method for forming a high-performance surface acoustic wave filter, wherein the surface acoustic wave filter formed by the forming method can block the transmission of bulk waves while improving the withstand power.

[0005] To solve the first technical problem mentioned above, the technical solution of the present invention is: a high-performance surface acoustic wave filter, comprising a substrate layer, a piezoelectric layer and a resonator metal layer, the piezoelectric layer is arranged above the substrate layer, the resonator metal layer is arranged above the piezoelectric layer, the upper surface of the electrode connection area in the resonator metal layer is also covered with a covering metal layer, and a channel cavity is also arranged on the substrate layer below the resonator metal layer, and the range of the channel cavity covers the interdigital transducer of the resonator metal layer.

[0006] As a preferred solution, an upper thermally conductive metal layer is provided at the bottom of the piezoelectric layer within the channel cavity, both sides of the upper thermally conductive metal layer are supported by the piezoelectric layer, and the upper surface of the upper thermally conductive metal layer is flush with the upper surface of the piezoelectric layer.

[0007] As a preferred solution, the side walls and bottom walls of the channel cavity are also covered with side thermal conductive metal layers and a lower thermal conductive metal layer, respectively; an upper thermal conductive metal layer is provided at the bottom of the piezoelectric layer within the channel cavity; both sides of the upper thermal conductive metal layer are supported by the piezoelectric layer; the upper surface of the upper thermal conductive metal layer is flush with the upper surface of the piezoelectric layer; and the upper thermal conductive metal layer is connected to the side thermal conductive metal layer and the lower thermal conductive metal layer.

[0008] As a preferred solution, the thickness of the upper heat-conducting metal layer and the lower heat-conducting metal layer is the same and greater than or equal to the side heat-conducting metal layer.

[0009] As a preferred solution, the upper heat-conducting metal layer, the lower heat-conducting metal layer and the side heat-conducting metal layer are made of the same material and are selected from single substances such as gold, silver, copper, aluminum, chromium, and titanium, or alloys or composite layers of the above single substances.

[0010] As a preferred solution, the cross section of the channel cavity is an inverted trapezoid.

[0011] As a preferred solution, the substrate layer includes a first substrate layer located below and a second substrate layer located above, and the channel cavity is arranged on the second substrate layer.

[0012] As a preferred solution, the first substrate layer is a high-resistance silicon layer, and the second substrate layer is one or more of silicon dioxide, silicon nitride, and silicon oxynitride.

[0013] After adopting the above technical scheme, the effect of the present invention is: since the upper surface of the electrode connection area in the resonator metal layer is also covered with a covering metal layer, and since the covering metal layer does not need to consider the piezoelectric conversion effect, the overall cross-sectional area of ​​the electrode connection area is relatively large, and the loss of signal transmission energy in this area is relatively small, thereby reducing the resistivity, and a channel cavity is also provided on the substrate layer below the resonator metal layer, and the range of the channel cavity covers the interdigital transducer of the resonator metal layer. The existence of the channel cavity can block the downward transmission of the body wave, thereby improving the quality factor of the filter.

[0014] Furthermore, since an upper thermally conductive metal layer is provided at the bottom of the piezoelectric layer within the range of the channel cavity, both sides of the upper thermally conductive metal layer are supported by the piezoelectric layer, and the upper surface of the upper thermally conductive metal layer is flush with the upper surface of the piezoelectric layer. Therefore, when a high-power signal passes through the resonator metal layer, a large amount of heat will be generated, and this heat will be transferred to the surrounding area. When the heat is transferred through the piezoelectric layer, it will be transferred to the upper thermally conductive metal layer. The upper thermally conductive metal layer can provide good heat dissipation, thereby increasing the tolerable power of the resonator.

[0015] Furthermore, since the side walls and bottom walls of the channel cavity are also covered with the side heat-conducting metal layer and the lower heat-conducting metal layer respectively, the bottom of the piezoelectric layer within the channel cavity is provided with an upper heat-conducting metal layer, both sides of the upper heat-conducting metal layer are supported by the piezoelectric layer, the upper surface of the upper heat-conducting metal layer is flush with the upper surface of the piezoelectric layer, and the upper heat-conducting metal layer is connected to the side heat-conducting metal layer and the lower heat-conducting metal layer. Similarly, the heat generated by the resonator metal layer can be better transferred to the side heat-conducting metal layer and the lower heat-conducting metal layer through the upper heat-conducting metal layer, and finally transferred to the substrate layer, thereby improving the thermal conductivity. This structure has good heat dissipation performance, and the tolerable power of the resonator metal layer is greatly improved.

[0016] Since the cross section of the channel cavity is an inverted trapezoid, the channel cavity is wide at the top and narrow at the bottom, so that the width of the upper heat-conducting metal layer is sufficient to cover the resonator metal layer while the channel cavity is not too large, so that the support of the overall structure is more reliable.

[0017] In order to solve the above second technical problem, the technical solution of the present invention is: to provide a high-performance surface acoustic wave filter molding method, the molding method is used to mold the above high-performance surface acoustic wave filter, comprising the following steps:

[0018] S1. providing a substrate layer and forming a channel cavity by vapor deposition or sputtering process;

[0019] S2, filling the channel cavity with a sacrificial layer;

[0020] S3, forming a layer of metal on the upper surface of the sacrificial layer by vapor deposition or sputtering process to form an upper heat-conducting metal layer, wherein the surface of the upper heat-conducting metal layer is flush with the upper surface of the substrate layer;

[0021] S4, making a through hole in the upper heat-conducting metal layer, and leading out the sacrificial layer in the through hole cavity;

[0022] S5, bonding the piezoelectric wafer to the surface of the substrate layer and the upper thermal conductive metal layer by using a crystal ion implantation stripping technique to form a piezoelectric layer;

[0023] S6. Generating a resonator metal layer and a covering metal layer on the surface of the piezoelectric layer by a photolithography process.

[0024] Preferably, step S1-2 is added between step S1 and step S2, and step S1-2 is to generate a lower heat-conducting metal layer and a side heat-conducting metal layer on the surface of the channel cavity by vapor deposition or sputtering process.

[0025] After adopting the above technical solution, the effect of the present invention is that the filter formed by the forming method can block the transmission of body waves and improve the withstand power at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0027] Figure 1 is a schematic structural diagram of Embodiment 1 of the present invention;

[0028] Figure 2 is a schematic structural diagram of Embodiment 1 of the present invention;

[0029] In the accompanying drawings: 10, covering metal layer; 20, piezoelectric layer; 30, second substrate layer; 40, first substrate layer; 50, channel cavity; 60, resonator metal layer; 70, upper thermal conductive metal layer; 80, side thermal conductive metal layer; 90, lower thermal conductive metal layer. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below through specific examples.

[0031] Embodiment 1

[0032] like Figure 1 As shown, a high-performance surface acoustic wave filter includes a substrate layer, a piezoelectric layer 20 and a resonator metal layer 60, wherein the piezoelectric layer 20 is arranged above the substrate layer, and the resonator metal layer 60 is arranged above the piezoelectric layer 20, wherein the resonator metal layer 60 includes an interdigital transducer and a reflective grating arranged on both sides of the interdigital transducer, and the upper surface of the electrode connection area in the resonator metal layer 60 is also covered with a covering metal layer 10, and the covering metal layer 10 increases the cross-sectional area of ​​the electrode connection area, thereby reducing the resistivity and reducing the power transmission loss. A channel cavity 50 is also arranged on the substrate layer below the resonator metal layer 60, and the range of the channel cavity 50 covers the interdigital transducer of the resonator metal layer 60.

[0033] In this embodiment, an upper thermal conductive metal layer 70 is provided at the bottom of the piezoelectric layer 20 within the channel cavity 50 , and both sides of the upper thermal conductive metal layer 70 are supported by the piezoelectric layer 20 , and the upper surface of the upper thermal conductive metal layer 70 is flush with the upper surface of the piezoelectric layer 20 .

[0034] The upper heat-conducting metal layer 70 may be made of a single substance selected from gold, silver, copper, aluminum, chromium, titanium, or an alloy or composite layer of the above single substances. The piezoelectric layer 20 may be made of piezoelectric materials such as lithium tantalate and lithium niobate.

[0035] like Figure 1 As shown, in this embodiment, the cross section of the channel cavity 50 is an inverted trapezoid.

[0036] The substrate layer includes a first substrate layer 40 located at the bottom and a second substrate layer 30 located at the top, and the channel cavity 50 is arranged on the second substrate layer 30. The first substrate layer 40 is a high-resistance silicon layer, which also has good thermal conductivity, and the second substrate layer 30 is one or more of silicon dioxide, silicon nitride, and silicon oxynitride.

[0037] The filter forming method in this embodiment is as follows: S1, providing a substrate layer, and forming a channel cavity 50 by vapor deposition or sputtering process; wherein, since the substrate layer includes a first substrate layer 40 and a second substrate layer 30, the formation of the channel cavity 50 can be formed by directly forming the second substrate layer on the first substrate layer by vapor deposition or sputtering process, thereby forming the channel cavity 50;

[0038] S2, filling the channel cavity 50 with a sacrificial layer;

[0039] S3, forming a layer of metal on the upper surface of the sacrificial layer by vapor deposition or sputtering process to form an upper heat-conducting metal layer 70, wherein the surface of the upper heat-conducting metal layer 70 is flush with the upper surface of the substrate layer;

[0040] S4, making a through hole in the upper heat-conducting metal layer 70, and leading out the sacrificial layer in the through hole cavity;

[0041] S5, bonding the piezoelectric wafer to the surface of the substrate layer and the upper heat-conducting metal layer 70 by using a crystal ion implantation lift-off technique to form a piezoelectric layer 20;

[0042] S6 . Form a resonator metal layer 60 and a cover metal layer 10 on the surface of the piezoelectric layer 20 by a photolithography process.

[0043] Among them, vapor deposition, sputtering process, crystal ion implantation stripping technology and photolithography process are all conventional and mature processes of semiconductors at present, and will not be described in detail again.

[0044] Embodiment 2

[0045] This embodiment has the same basic structure as that of the first embodiment, except that in this embodiment, the side walls and the bottom wall of the channel cavity 50 are also covered with a side heat-conducting metal layer 80 and a lower heat-conducting metal layer 90, respectively, and an upper heat-conducting metal layer 70 is provided at the bottom of the piezoelectric layer 20 within the channel cavity 50, and both sides of the upper heat-conducting metal layer 70 are supported by the piezoelectric layer 20, the upper surface of the upper heat-conducting metal layer 70 is flush with the upper surface of the piezoelectric layer 20, and the upper heat-conducting metal layer 70 is connected to the side heat-conducting metal layer 80 and the lower heat-conducting metal layer 90.

[0046] The thickness of the upper heat-conducting metal layer 70 and the lower heat-conducting metal layer 90 are the same and are greater than or equal to the side heat-conducting metal layer 80. The upper heat-conducting metal layer 70, the lower heat-conducting metal layer 90 and the side heat-conducting metal layer 80 are made of the same material and are selected from a single substance of gold, silver, copper, aluminum, chromium, titanium, or an alloy or a composite layer of the above single substances.

[0047] The molding method in this embodiment is to add step S1-2 between step S1 and step S2 in the molding method in embodiment 1. Step S1-2 is to form a lower heat-conducting metal layer 90 and a side heat-conducting metal layer 80 on the surface of the channel cavity 50 by vapor deposition or sputtering. After the lower heat-conducting metal layer 90 and the side heat-conducting metal layer 80 are formed, a sacrificial layer is filled, and then the subsequent steps are continued to finally form the inlet and outlet. Figure 2 The filter in .

[0048] The solution in the present invention has at least the following advantages over the current conventional filter methods: 1. The upper surface of the electrode connection area is also covered with a covering metal layer 10, which increases the thickness of the electrode connection area and the cross-sectional area, thereby reducing the resistivity and reducing the power transmission loss; 2. A channel cavity 50 is provided to block the transmission of body waves and improve the quality factor of the filter; 3. An upper thermal conductive metal layer 70, a lower thermal conductive metal layer 90 and a side thermal conductive metal layer 80 are added to improve the thermal conductivity and meet the heat dissipation requirements during high-power signal filtering.

[0049] The above-described embodiments are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Various modifications and alterations to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A high-performance surface acoustic wave filter, comprising a substrate layer, a piezoelectric layer and a resonator metal layer, wherein the piezoelectric layer is arranged above the substrate layer, and the resonator metal layer is arranged above the piezoelectric layer, characterized in that: The upper surface of the electrode connection area in the resonator metal layer is also covered with a covering metal layer, and a channel cavity is also arranged on the substrate layer below the resonator metal layer, and the range of the channel cavity covers the interdigital transducer of the resonator metal layer.

2. A high performance surface acoustic wave filter as claimed in claim 1, characterized in that: An upper heat-conducting metal layer is arranged at the bottom of the piezoelectric layer within the channel cavity, both sides of the upper heat-conducting metal layer are supported by the piezoelectric layer, and the upper surface of the upper heat-conducting metal layer is flush with the upper surface of the piezoelectric layer.

3. A high performance surface acoustic wave filter as claimed in claim 1, characterized in that: The side walls and bottom walls of the channel cavity are also covered with a side heat-conducting metal layer and a lower heat-conducting metal layer, respectively; an upper heat-conducting metal layer is arranged at the bottom of the piezoelectric layer within the range of the channel cavity; both sides of the upper heat-conducting metal layer are supported by the piezoelectric layer; the upper surface of the upper heat-conducting metal layer is flush with the upper surface of the piezoelectric layer; and the upper heat-conducting metal layer is connected to the side heat-conducting metal layer and the lower heat-conducting metal layer.

4. A high performance surface acoustic wave filter as claimed in claim 3, characterized in that: The thickness of the upper heat-conducting metal layer and the lower heat-conducting metal layer is the same and is greater than or equal to the side heat-conducting metal layer.

5. A high performance surface acoustic wave filter as claimed in claim 4, characterized in that: The upper heat-conducting metal layer, the lower heat-conducting metal layer and the side heat-conducting metal layer are made of the same material and are selected from single substances such as gold, silver, copper, aluminum, chromium and titanium, or alloys or composite layers of the above single substances.

6. A high performance surface acoustic wave filter as claimed in claim 1, characterized in that: The cross section of the channel cavity is an inverted trapezoid.

7. A high performance surface acoustic wave filter as claimed in claim 1, characterized in that: The substrate layer comprises a first substrate layer located at a lower portion and a second substrate layer located at an upper portion, and the channel cavity is arranged on the second substrate layer.

8. A high performance surface acoustic wave filter as claimed in claim 7, characterized in that: The first substrate layer is a high-resistance silicon layer, and the second substrate layer is one or more of silicon dioxide, silicon nitride, and silicon oxynitride.

9. A method for forming a high-performance surface acoustic wave filter, characterized in that: The molding method is used to mold the high-performance surface acoustic wave filter in claim 1, comprising the following steps: S1. providing a substrate layer and forming a channel cavity by vapor deposition or sputtering process; S2, filling the channel cavity with a sacrificial layer; S3, forming a layer of metal on the upper surface of the sacrificial layer by vapor deposition or sputtering process to form an upper heat-conducting metal layer, wherein the surface of the upper heat-conducting metal layer is flush with the upper surface of the substrate layer; S4, making a through hole in the upper heat-conducting metal layer, and leading out the sacrificial layer in the through hole cavity; S5, bonding the piezoelectric wafer to the surface of the substrate layer and the upper thermal conductive metal layer by using a crystal ion implantation stripping technique to form a piezoelectric layer; S6. Generating a resonator metal layer and a covering metal layer on the surface of the piezoelectric layer by a photolithography process.

10. A method for forming a high-performance surface acoustic wave filter as claimed in claim 9, characterized in that: A step S1-2 is added between the step S1 and the step S2. The step S1-2 is to form a lower heat-conducting metal layer and a side heat-conducting metal layer on the surface of the channel cavity by vapor deposition or sputtering process.

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