CN117526898A - Surface acoustic wave filter and filter element - Google Patents
Surface acoustic wave filter and filter element Download PDFInfo
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- CN117526898A CN117526898A CN202410011775.2A CN202410011775A CN117526898A CN 117526898 A CN117526898 A CN 117526898A CN 202410011775 A CN202410011775 A CN 202410011775A CN 117526898 A CN117526898 A CN 117526898A
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- 238000010897 surface acoustic wave method Methods 0.000 title claims abstract description 141
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 70
- 239000011241 protective layer Substances 0.000 claims abstract description 49
- 239000000758 substrate Substances 0.000 claims abstract description 40
- 239000010410 layer Substances 0.000 claims abstract description 35
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 35
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 32
- 229910052581 Si3N4 Inorganic materials 0.000 claims abstract description 17
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims abstract description 17
- WSMQKESQZFQMFW-UHFFFAOYSA-N 5-methyl-pyrazole-3-carboxylic acid Chemical group CC1=CC(C(O)=O)=NN1 WSMQKESQZFQMFW-UHFFFAOYSA-N 0.000 claims description 10
- 229910000881 Cu alloy Inorganic materials 0.000 claims description 6
- WPPDFTBPZNZZRP-UHFFFAOYSA-N aluminum copper Chemical compound [Al].[Cu] WPPDFTBPZNZZRP-UHFFFAOYSA-N 0.000 claims description 6
- 238000000034 method Methods 0.000 description 29
- 230000008569 process Effects 0.000 description 28
- 230000000052 comparative effect Effects 0.000 description 18
- 239000000463 material Substances 0.000 description 11
- 238000012360 testing method Methods 0.000 description 8
- 238000013461 design Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
- 230000009977 dual effect Effects 0.000 description 4
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 4
- 230000008878 coupling Effects 0.000 description 3
- 238000010168 coupling process Methods 0.000 description 3
- 238000005859 coupling reaction Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 230000008570 general process Effects 0.000 description 3
- 238000004891 communication Methods 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 238000002604 ultrasonography Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/46—Filters
- H03H9/64—Filters using surface acoustic waves
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
- H03H3/04—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks for obtaining desired frequency or temperature coefficient
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- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Abstract
The invention relates to the technical field of electronics, in particular to a surface acoustic wave filter and a filter element, wherein silicon dioxide is arranged as a first protective layer to cover a substrate and an electrode of the surface acoustic wave filter, so that the first protective layer reduces the central frequency of the surface acoustic wave filter to be lower than the target frequency required to be achieved before a second protective layer is arranged in a covering manner, the surface acoustic wave filter is protected, and then a layer of silicon nitride is arranged on the first protective layer in a covering manner as a second protective layer to correct the central frequency of the surface acoustic wave filter, so that the central frequency of the surface acoustic wave filter reaches the required target frequency, and the central frequency can be corrected to the target frequency without adjusting the thickness of the silicon dioxide.
Description
Technical Field
The invention belongs to the technical field of electronics, and particularly relates to a surface acoustic wave filter and a filter element.
Background
A surface acoustic wave (Surface Acoustic Wave, SAW) is a type of elastic wave that propagates along the surface of an object. SAW technology is an emerging scientific technology that was developed only at the end of the 60 s of the last century and is a discipline of ultrasound and electronics. Since high quality SAW chips can be mass-produced by using photolithography, various SAW devices are rapidly introduced and put into practical use. SAW devices can be miniaturized and made multifunctional by using SAW to simulate various functions of electronics. The SAW device can realize various complex signal processing functions, has the characteristics of low power consumption, low cost, light weight, small size, excellent performance and the like, becomes one of key core devices of an RF front end of an integrated, miniaturized and high-performance wireless communication system, and is widely applied to the fields of civil consumer goods, commercial equipment, military systems and the like.
The preparation process of the surface acoustic wave filter can be divided into a common process, a temperature compensation process and a high-performance process. The common process adopts lithium tantalate as the substrate of the surface acoustic wave filter, has the characteristics of low cost, simple process and the like, and makes the surface acoustic wave filter of the common process a mainstream product. In the process of processing the surface acoustic wave filter, before the silicon dioxide is covered, the center frequency of the surface acoustic wave filter is higher than the target frequency, i.e., the center frequency of the surface acoustic wave filter needs to be reduced by the silicon dioxide. After the silicon dioxide is covered, the center frequency of the surface acoustic wave filter cannot reach the target frequency accurately, and if the center frequency is not corrected, the surface acoustic wave filter is scrapped due to the fact that the frequency is not correct, the cost is wasted, and loss is caused. The prior art carries out center frequency correction by continuously adjusting the thickness of silicon dioxide. However, the thickness of the silicon dioxide covered on the surface acoustic wave filter needs to be strictly set according to the design requirement, and for the surface acoustic wave filter of the common process, the bandwidth of the surface acoustic wave filter deviates from the designed target bandwidth due to the excessively thick silicon dioxide, so that the performance is deteriorated, the surface acoustic wave filter cannot be effectively protected due to the excessively thin silicon dioxide, and the reliability of the device is reduced. It is known that the conventional surface acoustic wave filter of the conventional general process cannot correct the center frequency to the target frequency without affecting the performance and reliability of the device.
Disclosure of Invention
In order to solve the above-mentioned prior art problems, the present invention provides a surface acoustic wave filter and a multiplexer, and the technical scheme is as follows:
in a first aspect, an embodiment of the present invention provides a surface acoustic wave filter, including:
a substrate;
an electrode disposed on one side of the substrate;
the first protective layer is silicon dioxide and covers the electrode and the side of the substrate, on which the electrode is arranged;
the second protection layer is arranged on one side of the first protection layer far away from the substrate in a covering manner, and is silicon nitride;
wherein the first protective layer is used for reducing the center frequency of the SAW filter below the target frequency required to be achieved before the second protective layer is arranged in a covering manner.
In one embodiment, the substrate is lithium tantalate and the thickness of the substrate is 200um.
In one embodiment, the electrode is an aluminum copper alloy and the thickness of the electrode is 2100A.
In one embodiment, the first protective layer has a thickness of 150A.
In one embodiment, the second protective layer has a thickness of 100A.
In one embodiment, the circuit structure of the surface acoustic wave filter includes a dual mode surface acoustic wave filter.
In one embodiment, the circuit structure of the surface acoustic wave filter further includes a first ground terminal, a second ground terminal, and a third ground terminal;
the dual-mode surface acoustic wave filter is a 5-order dual-mode surface acoustic wave filter, and the dual-mode surface acoustic wave filter is simultaneously connected with a first grounding terminal, a second grounding terminal and a third grounding terminal, wherein the second grounding terminal and the third grounding terminal are grounded in common.
In one embodiment, the circuit structure of the surface acoustic wave filter further includes a first series arm, a second series arm, a third series arm, a first parallel arm, a fourth ground terminal, an input terminal, and an output terminal;
the first end of the first series arm is connected with the input terminal, the second end of the first series arm is connected with the first end of the first parallel arm, the second end of the first parallel arm is connected with the fourth ground terminal, the first end of the first parallel arm is also connected with the first end of the second series arm, the second end of the second series arm is connected with the input end of the dual-mode SAW filter, the output end of the dual-mode SAW filter is connected with the first end of the third series arm, and the second end of the third series arm is connected with the output terminal.
In one embodiment, the third series arm is provided with a surface acoustic wave resonator.
In a second aspect, an embodiment of the present invention provides a filter element including the surface acoustic wave filter of the first aspect.
The method has the advantages that the silicon dioxide is arranged to serve as the first protective layer to cover the substrate and the electrode of the surface acoustic wave filter, the first protective layer is used for reducing the center frequency of the surface acoustic wave filter to be lower than the target frequency required to be achieved before the second protective layer is arranged in a covering mode, the surface acoustic wave filter is protected, then the silicon nitride is arranged to serve as the second protective layer to cover the first protective layer to correct the center frequency of the surface acoustic wave filter, so that the center frequency of the surface acoustic wave filter reaches the target frequency required, the thickness of the silicon dioxide is not required to be adjusted, namely the center frequency of the surface acoustic wave filter can be corrected to the target frequency by covering the silicon nitride on the silicon dioxide after the thickness of the silicon dioxide is strictly arranged according to design requirements, and device performance and reliability are not affected.
Drawings
In the drawings, the same reference numerals refer to the same or similar parts or elements throughout the several views unless otherwise specified. The figures are not necessarily drawn to scale. It is appreciated that these drawings depict only some embodiments according to the disclosure and are not therefore to be considered limiting of its scope.
Fig. 1 is a schematic cross-sectional view of a surface acoustic wave filter according to an embodiment of the present invention;
fig. 2 is a schematic cross-sectional structure of a conventional surface acoustic wave filter;
fig. 3 is a schematic circuit diagram of a surface acoustic wave filter according to an embodiment of the present invention;
FIG. 4 is a schematic diagram showing the comparison of the S-parameter curve of the SAW filter of the present invention with that of the SAW filter of the comparative example;
fig. 5 is a schematic diagram showing the comparison of the passband curves of the surface acoustic wave filter according to the embodiment of the present invention and the passband curves of the surface acoustic wave filter according to the comparative example.
Reference numerals: 101. a substrate; 102. an electrode; 103. a first protective layer; 104. a second protective layer; DMS, dual mode surface acoustic wave filter; 4. a first ground terminal; 5. a second ground terminal; 6. a third ground terminal; s1, a first series arm; s2, a second series arm; s3, a third series arm; p1, a first parallel arm; 3. a fourth ground terminal; 1. an input terminal; 2. and an output terminal.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In a first aspect, an embodiment of the present invention provides a surface acoustic wave filter. Fig. 1 shows a cross-sectional structure of a surface acoustic wave filter according to an embodiment of the present invention. As shown in fig. 1, the surface acoustic wave filter may include:
a substrate 101;
an electrode 102, the electrode 102 being disposed on one side of the substrate 101;
a first protective layer 103, the first protective layer 103 being silicon dioxide, the first protective layer 103 covering the electrode 102 and the side of the substrate 101 on which the electrode 102 is provided;
the second protection layer 104, the second protection layer 104 is arranged on one side of the first protection layer 103 far away from the substrate 101 in a covering manner, and the second protection layer 104 is silicon nitride;
the first protection layer 103 is used for protecting the surface acoustic wave filter, improving the reliability of the surface acoustic wave filter, and reducing the center frequency of the surface acoustic wave filter to be lower than the required target frequency before the second protection layer 104 is arranged in a covering manner. The thicker the first protective layer 103, the lower the center frequency of the surface acoustic wave filter. Meanwhile, since silicon dioxide has strong characteristics, if the first protective layer 103 is too thick for a surface acoustic wave filter of a general process, the bandwidth of the surface acoustic wave filter deviates from the designed target bandwidth, so that the performance of the surface acoustic wave filter is deteriorated, and even the product is not usable. Therefore, the thickness of the first protection layer 103 needs to be strictly set according to the design requirement, and the thickness of the first protection layer 103 in the embodiment of the present invention is strictly set according to the specific substrate 101 material, substrate 101 thickness, electrode 102 material and electrode 102 thickness, so that the bandwidth of the surface acoustic wave filter is not affected, and meanwhile, the effective protection effect on the surface acoustic wave filter can be achieved, and the center frequency of the surface acoustic wave filter is reduced to be lower than the required target frequency.
The second protective layer 104 is used to correct the center frequency of the surface acoustic wave filter. It can be understood that the silicon nitride layer is covered on the side of the first protection layer 103 away from the substrate 101, so that the center frequency of the saw filter can be raised, and the center frequency of the saw filter can reach the target frequency by adjusting the thickness of the second protection layer 104, without adjusting the thickness of the first protection layer 103, and without affecting the reliability and the device performance of the saw filter. In addition, since the second protection layer 104 is silicon nitride, and the temperature drift coefficient of the silicon nitride is lower than that of the piezoelectric material (such as lithium niobate or lithium tantalate) used in the substrate 101 of the surface acoustic wave filter, covering the second protection layer 104 can effectively reduce the temperature drift coefficient of the surface acoustic wave filter and improve the stability of the surface acoustic wave filter.
It is to be noted that fig. 2 shows a cross-sectional structure of a conventional surface acoustic wave filter. Referring to fig. 2, a conventional surface acoustic wave filter has a silicon dioxide protective layer covering an electrode of a substrate. From the foregoing, before the silica is covered, the center frequency of the saw filter is higher than the target frequency, that is, the center frequency of the saw filter can be reduced by covering the silica, but the thickness of the silica needs to be strictly set according to the design requirement, which makes the reduced center frequency often not reach the target frequency accurately. At this time, the existing technology needs to continuously adjust the thickness of the silicon dioxide to correct the center frequency. However, for the surface acoustic wave filter of the common process, the bandwidth of the surface acoustic wave filter deviates from the designed target bandwidth due to the excessively thick silicon dioxide, so that the performance is deteriorated, the surface acoustic wave filter cannot be effectively protected due to the excessively thin silicon dioxide, and the reliability of a device is reduced, so that the conventional surface acoustic wave filter of the common process cannot correct the center frequency to the target frequency on the premise of not affecting the performance and the reliability of the device. In the surface acoustic wave filter of the embodiment of the invention, silicon dioxide is arranged as the first protection layer 103 to cover the substrate 101 and the electrode 102 of the surface acoustic wave filter, so that the first protection layer 103 reduces the central frequency of the surface acoustic wave filter to be lower than the target frequency required to be achieved before the second protection layer 104 is arranged in a covering manner, the surface acoustic wave filter is protected, and then a layer of silicon nitride is arranged on the first protection layer 103 as the second protection layer 104 to modify the central frequency of the surface acoustic wave filter, so that the central frequency of the surface acoustic wave filter reaches the required target frequency, and the central frequency can be modified to the target frequency without adjusting the thickness of the silicon dioxide.
Alternatively, in some embodiments, the substrate 101 is lithium tantalate and the thickness of the substrate 101 is 200um.
It is understood that the process of manufacturing the surface acoustic wave filter can be classified into three processes of a general process, a temperature compensation process, and a high performance process. The common process adopts lithium tantalate as the substrate 101 of the surface acoustic wave filter, and has the characteristics of low cost and simple process, so that the surface acoustic wave filter of the common process becomes a main stream product; the substrate 101 used in the temperature compensation process is lithium niobate, and has the characteristics of low power consumption, complex process and higher cost; the high performance process uses the silicon substrate 101 and the high and low resistance layer structure, and has the characteristics of low power consumption and high cost. From the foregoing, it is known that the excessive thickness of the silicon dioxide protection layer of the surface acoustic wave filter in the conventional process may cause the bandwidth to deviate from the target bandwidth, resulting in the deterioration of the device performance, and at this time, the substrate 101 material needs to be changed from lithium tantalate to lithium niobate so that the bandwidth does not deviate from the target bandwidth, i.e., the surface acoustic wave filter in the temperature compensation process can withstand the thicker silicon dioxide protection layer. Meanwhile, the cutting angle of lithium niobate of the surface acoustic wave filter of the temperature compensation process is different from that of lithium tantalate, and the temperature compensation process has controllable frequency selection, so that the surface acoustic wave filter of the temperature compensation process can correct the center frequency to the target frequency on the premise of not affecting the performance and reliability of the device. However, the temperature compensation type surface acoustic wave filter has higher cost compared with the surface acoustic wave filter of the common process, particularly the cost is obviously improved in mass production, and the embodiment of the invention can correct the center frequency to the target frequency on the premise of not influencing the performance and the reliability of the device on the basis of the surface acoustic wave filter of the common process, namely the same effect as the surface acoustic wave filter of the temperature compensation type process can be realized, and the cost is greatly reduced.
Further, in some embodiments, the electrode 102 is an aluminum copper alloy and the thickness of the electrode 102 is 2100A.
It should be noted that, in the embodiment of the present invention, the aluminum-copper alloy is used as the electrode 102, and the thickness of the electrode 102 is set to 2100A, so that the surface acoustic wave filter can obtain the best design performance and has low loss.
Further, in some embodiments, the first protective layer 103 has a thickness of 150A.
It will be appreciated that in setting the thickness of the first protective layer 103, both the reliability and the performance of the device are considered. Wherein, the silicon dioxide (the first protective layer 103) does not have enough protection effect on the electrode 102 when the thickness is less than 100A; above 300A, the device performance may be degraded. This is because when the thickness of the first protective layer 103 is increased, molecules of the silicon dioxide, the electrode 102 and the substrate 101 are displaced by interaction force between particles, which affects the electromechanical coupling coefficient of the resonator and thus changes the device bandwidth, so that the thickness of the first protective layer 103 is suitably set at 150A.
From the foregoing, it can be seen that the thickness of the first protective layer 103 is strictly set according to the specific substrate 101 material, substrate 101 thickness, electrode 102 material, and electrode 102 thickness. At this thickness, the first protective layer 103 does not affect the bandwidth of the surface acoustic wave filter and can effectively protect the surface acoustic wave filter, while also reducing the center frequency of the surface acoustic wave filter below the desired target frequency.
Optionally, in some embodiments, the second protective layer 104 has a thickness of 100A.
The second protective layer 104 is disposed on the side of the first protective layer 103 away from the substrate 101, and mainly serves to correct the frequency of the device. If the thickness of the silicon nitride (second passivation layer 104) is too thick, molecules of the silicon nitride, silicon dioxide, the electrode 102 and the substrate 101 are displaced by the interaction force between particles, which affects the electromechanical coupling coefficient of the resonator and further changes the device bandwidth.
The frequency of the resonator is determined by the thickness of the electrode, the material and the like, and can be expressed by the following formula:
v=(A1*hm/λ+ A2*hsio2/λ+A3*hsin/λ+B)*f
where v is the speed of sound, λ is the wavelength, f is the frequency, hm is the thickness of the electrode 102, hsio2 is the thickness of the first protective layer 103, hsin is the thickness of the second protective layer 104, and A1, A2, A3, B are coefficients.
Fig. 3 shows a circuit configuration of a surface acoustic wave filter according to an embodiment of the present invention. Referring to fig. 3, optionally, in some embodiments, the circuit structure of the surface acoustic wave filter comprises a dual mode surface acoustic wave (Dual ModeSurface Acoustic Wave, DMS) filter.
It can be understood that the circuit structure of the surface acoustic wave filter in the embodiment of the invention adopts the DMS filter, a wider working bandwidth can be realized through the combination of each resonant mode, the input or output of the balanced amplifier can be matched through the balanced setting of the input and the output, and simultaneously, the lower insertion loss and the good out-of-band rejection characteristic can be realized through the coupling of two identical resonant modes in the longitudinal direction.
With continued reference to fig. 3, optionally, in some embodiments, the circuit structure of the saw filter further includes a first ground terminal 4, a second ground terminal 5, and a third ground terminal 6, and the DMS filter is a 5-order DMS filter.
Wherein the DMS filter connects the first ground terminal 4, the second ground terminal 5 and the third ground terminal 6 simultaneously, the second ground terminal 5 and the third ground terminal 6 being commonly grounded.
It will be appreciated that the DMS filter itself may be used as a separate filter with the signal and ground terminals isolated by an insulating layer. The more the grounding terminals of the DMS filter are, the more stable the out-of-band suppression effect is; the closer the ground terminal of the DMS filter is to the ground, the more stable the out-of-band rejection thereof. The DMS filter of the embodiment of the invention is simultaneously connected with the first grounding terminal 4, the second grounding terminal 5 and the third grounding terminal 6, and the second grounding terminal 5 and the third grounding terminal 6 are commonly grounded, so that the upper end and the lower end of the DMS filter are both connected with the grounding terminals, and the stability of the out-of-band rejection performance of the DMS filter is improved.
Optionally, in some embodiments, the circuit structure of the surface acoustic wave filter further includes a first series arm S1, a second series arm S2, a third series arm S3, a first parallel arm P1, a fourth ground terminal 3, an input terminal 1, and an output terminal 2.
The first end of the first series arm S1 is connected to the input terminal 1, the second end of the first series arm S1 is connected to the first end of the first parallel arm P1, the second end of the first parallel arm P1 is connected to the fourth ground terminal 3, the first end of the first parallel arm P1 is also connected to the first end of the second series arm S2, the second end of the second series arm S2 is connected to the input end of the DMS filter, the output end of the DMS filter is connected to the first end of the third series arm S3, and the second end of the third series arm S3 is connected to the output terminal 2.
Optionally, in some embodiments, the third series arm S3 is provided with a surface acoustic wave resonator.
It can be understood that, in the embodiment of the present invention, by disposing the saw resonator in the third series arm S3, signals in a specific frequency range can be selectively transferred, and the signals can be suppressed well at other frequencies.
Fig. 4 is a schematic diagram showing a comparison between an S-parameter curve of a surface acoustic wave filter according to an embodiment of the present invention and an S-parameter curve of a surface acoustic wave filter according to a comparative example. Referring to fig. 4, wherein the abscissa is frequency in GHz; the ordinate is the S parameter, and the unit is dB; the S-parameter curve of the surface acoustic wave filter of the specific embodiment of the present invention is represented by a solid line, and the S-parameter curve of the surface acoustic wave filter of the comparative example is represented by a broken line; the surface acoustic wave filter of the embodiment of the present invention is provided with a lithium tantalate substrate having a thickness of 200um, an aluminum copper alloy electrode having a thickness of 2100A, a first protective layer (silicon dioxide) having a thickness of 150A, and a second protective layer (silicon nitride) having a thickness of 100A, and the surface acoustic wave filter of the comparative example is provided with a lithium tantalate substrate having a thickness of 200um, an aluminum copper alloy electrode having a thickness of 2100A, and a silicon dioxide protective layer having a thickness of 150A. As shown in fig. 4, the S-parameter curve of the surface acoustic wave filter according to the embodiment of the present invention substantially coincides with the S-parameter curve of the surface acoustic wave filter according to the comparative example, that is, the surface acoustic wave filter according to the embodiment of the present invention does not affect the device performance after covering a layer of silicon nitride on the basis of the surface acoustic wave filter according to the comparative example.
Fig. 5 is a schematic diagram showing the passband curves of the saw filter according to the embodiment of the present invention compared with those of the saw filter according to the comparative example, that is, an enlarged view of the passband curves of the filter in fig. 4. As can be seen from fig. 5, the center frequency of the surface acoustic wave filter according to the embodiment of the present invention is higher than that of the surface acoustic wave filter according to the comparative example, and the loss is substantially uniform.
In addition, high and low temperature tests were performed on the surface acoustic wave filter of the specific embodiment of the present invention and the surface acoustic wave filter of the comparative example, so as to verify that the surface acoustic wave filter of the embodiment of the present invention can improve the temperature drift after covering a layer of silicon nitride on the basis of the surface acoustic wave filter of the comparative example. Specifically, the test data are shown in tables 1, 2 and 3. Wherein, table 1 is test data of the filter at normal temperature (25 degrees centigrade), table 2 is test data of the filter at low temperature (minus 30 degrees centigrade), and table 3 is test data of the filter at high temperature (85 degrees centigrade).
Table 1 test data for filters at normal temperature (25 degrees celsius)
| Material number | Loss @1164MHz | Loss @1187MHz | Loss @1189MHz | MAX LOSS(1164~1189 MHz) | Average value of Fc | TCF(ppm/℃) |
| Certain bid article | -1.13 | -1.24 | -1.28 | -1.33 | 1165.78 | 43.71 |
| Comparative example | -1.04 | -1.15 | -1.18 | -1.20 | 1176.33 | 31.93 |
| Examples | -1.12 | -1.13 | -1.24 | -1.26 | 1176.32 | 30.09 |
Table 2 test data for filters at low temperature (minus 30 degrees celsius)
| Material number | Loss @1164MHz | Loss @1187MHz | Loss @1189MHz | MAX LOSS(1164~1189 MHz) | Average value of Fc | Low Wen Pinpian |
| Certain bid article | -0.96 | -1.14 | -1.13 | -1.25 | 1169.01 | 3.23 |
| Comparative example | -0.96 | -0.98 | -1.02 | -1.05 | 1178.65 | 2.31 |
| Examples | -0.93 | -0.87 | -0.99 | -0.99 | 1178.54 | 2.23 |
Table 3 test data for filters at high temperature (85 degrees celsius)
| Material number | Loss @1164MHz | Loss @1187MHz | Loss @1189MHz | MAX LOSS(1164~1189 MHz) | Average value of Fc | High temperature frequency offset |
| Certain bid article | -1.366 | -1.40 | -1.41 | -1.45 | 1163.15 | 2.63 |
| Comparative example | -1.17 | -1.35 | -1.56 | -1.56 | 1174.33 | 2.01 |
| Examples | -1.21 | -1.36 | -1.49 | -1.50 | 1174.47 | 1.84 |
Wherein, TCF represents the temperature drift coefficient, and the formula is:
tcf= (low temperature frequency offset + high temperature frequency offset)/(high and low temperature difference center frequency at normal temperature) ×1000000
As can be seen from table 2, the low-temperature frequency offset of the surface acoustic wave filter according to the embodiment of the present invention is lower than the low Wen Pinpian of the surface acoustic wave filter according to the comparative example; as can be seen from table 3, the high temperature frequency offset of the surface acoustic wave filter according to the embodiment of the present invention is lower than the high Wen Pinpian of the surface acoustic wave filter of the comparative example. Therefore, according to the calculation formula of TCF, the temperature drift coefficient of the surface acoustic wave filter in the specific embodiment of the present invention is lower than that of the surface acoustic wave filter in the comparative example, and the surface acoustic wave filter in the embodiment of the present invention can improve the temperature drift after covering a layer of silicon nitride on the basis of the surface acoustic wave filter in the comparative example.
In summary, in the embodiment of the present invention, silicon dioxide is disposed as the first protective layer to cover the substrate and the electrode of the saw filter, so that the first protective layer reduces the center frequency of the saw filter to be lower than the target frequency required to be achieved before the second protective layer is disposed, and protects the saw filter, and then a layer of silicon nitride is disposed as the second protective layer on the first protective layer to modify the center frequency of the saw filter, so that the center frequency of the saw filter reaches the target frequency required, and the center frequency can be modified to the target frequency without adjusting the thickness of the silicon dioxide.
In a second aspect, an embodiment of the present invention provides a filter element including the surface acoustic wave filter of the first aspect.
In describing embodiments of the present invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "center", "top", "bottom", "inner", "outer", "inside", "outside", etc. indicate orientations or positional relationships based on the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Wherein "inside" refers to an interior or enclosed area or space. "peripheral" refers to the area surrounding a particular component or region.
In the description of embodiments of the present invention, the terms "first," "second," "third," "fourth" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first", "a second", "a third" and a fourth "may explicitly or implicitly include one or more such feature. In the description of the present invention, unless otherwise indicated, the meaning of "a plurality" is two or more.
In describing embodiments of the present invention, it should be noted that the terms "mounted," "connected," and "assembled" are to be construed broadly, as they may be fixedly connected, detachably connected, or integrally connected, unless otherwise specifically indicated and defined; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
In the description of embodiments of the invention, a particular feature, structure, material, or characteristic may be combined in any suitable manner in one or more embodiments or examples.
In describing embodiments of the present invention, it will be understood that the terms "-" and "-" are intended to be inclusive of the two numerical ranges, and that the ranges include the endpoints. For example, "A-B" means a range greater than or equal to A and less than or equal to B. "A-B" means a range of greater than or equal to A and less than or equal to B.
In the description of embodiments of the present invention, the term "and/or" is merely an association relationship describing an association object, meaning that three relationships may exist, e.g., a and/or B, may represent: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (10)
1. A surface acoustic wave filter, comprising:
a substrate;
an electrode disposed on one side of the substrate;
the first protective layer is silicon dioxide and covers the electrode and one side of the substrate, on which the electrode is arranged;
the second protection layer is arranged on one side, far away from the substrate, of the first protection layer in a covering mode, and the second protection layer is silicon nitride;
the first protective layer is used for reducing the center frequency of the surface acoustic wave filter to be lower than the target frequency required to be achieved before the second protective layer is arranged in a covering mode.
2. The surface acoustic wave filter according to claim 1, wherein the substrate is lithium tantalate and the thickness of the substrate is 200um.
3. The surface acoustic wave filter according to claim 2, wherein the electrode is an aluminum copper alloy, and the thickness of the electrode is 2100A.
4. A surface acoustic wave filter according to claim 3, wherein the first protective layer has a thickness of 150A.
5. The surface acoustic wave filter according to claim 4, wherein the thickness of the second protective layer is 100A.
6. The surface acoustic wave filter according to claim 1, wherein the circuit structure of the surface acoustic wave filter comprises a dual-mode surface acoustic wave filter.
7. The surface acoustic wave filter according to claim 6, wherein the circuit structure of the surface acoustic wave filter further comprises a first ground terminal, a second ground terminal, and a third ground terminal;
the dual-mode surface acoustic wave filter is a 5-order dual-mode surface acoustic wave filter, and the dual-mode surface acoustic wave filter is simultaneously connected with the first grounding terminal, the second grounding terminal and the third grounding terminal, wherein the second grounding terminal and the third grounding terminal are grounded in common.
8. The surface acoustic wave filter according to any one of claims 6 or 7, characterized in that the circuit structure of the surface acoustic wave filter further comprises a first series arm, a second series arm, a third series arm, a first parallel arm, a fourth ground terminal, an input terminal, and an output terminal;
the first end of the first series arm is connected with the input terminal, the second end of the first series arm is connected with the first end of the first parallel arm, the second end of the first parallel arm is connected with the fourth ground terminal, the first end of the first parallel arm is also connected with the first end of the second series arm, the second end of the second series arm is connected with the input end of the dual-mode SAW filter, the output end of the dual-mode SAW filter is connected with the first end of the third series arm, and the second end of the third series arm is connected with the output terminal.
9. The surface acoustic wave filter according to claim 8, wherein the third series arm is provided with a surface acoustic wave resonator.
10. A filter element comprising the surface acoustic wave filter according to any one of claims 1 to 9.
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| CN101821944A (en) * | 2007-10-18 | 2010-09-01 | 株式会社村田制作所 | Surface acoustic wave resonator and ladder type filter |
| CN103187944A (en) * | 2004-03-29 | 2013-07-03 | 株式会社村田制作所 | Boundary acoustic wave device manufacturing method |
| CN112511131A (en) * | 2021-02-05 | 2021-03-16 | 成都频岢微电子有限公司 | Duplexer with high isolation and high-pass band low-frequency side high-steepness |
| CN112532201A (en) * | 2021-02-07 | 2021-03-19 | 成都频岢微电子有限公司 | Layout structure for improving out-of-band rejection of surface acoustic wave receiving filter |
| CN117240251A (en) * | 2023-11-16 | 2023-12-15 | 成都频岢微电子有限公司 | Miniaturized layout structure of filter in module |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103187944A (en) * | 2004-03-29 | 2013-07-03 | 株式会社村田制作所 | Boundary acoustic wave device manufacturing method |
| CN101821944A (en) * | 2007-10-18 | 2010-09-01 | 株式会社村田制作所 | Surface acoustic wave resonator and ladder type filter |
| CN112511131A (en) * | 2021-02-05 | 2021-03-16 | 成都频岢微电子有限公司 | Duplexer with high isolation and high-pass band low-frequency side high-steepness |
| CN112532201A (en) * | 2021-02-07 | 2021-03-19 | 成都频岢微电子有限公司 | Layout structure for improving out-of-band rejection of surface acoustic wave receiving filter |
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