CN114640320A - Method for improving performance of FBAR filter - Google Patents
Method for improving performance of FBAR filter Download PDFInfo
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- CN114640320A CN114640320A CN202210305141.9A CN202210305141A CN114640320A CN 114640320 A CN114640320 A CN 114640320A CN 202210305141 A CN202210305141 A CN 202210305141A CN 114640320 A CN114640320 A CN 114640320A
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- 238000000034 method Methods 0.000 title claims abstract description 14
- 238000000137 annealing Methods 0.000 claims abstract description 37
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 16
- 238000001816 cooling Methods 0.000 claims abstract description 9
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 8
- 238000010438 heat treatment Methods 0.000 claims abstract description 7
- 238000002360 preparation method Methods 0.000 claims abstract description 6
- 238000004321 preservation Methods 0.000 claims description 9
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 3
- 238000000151 deposition Methods 0.000 claims description 3
- 238000000059 patterning Methods 0.000 claims description 3
- 238000001259 photo etching Methods 0.000 claims description 3
- 229910052710 silicon Inorganic materials 0.000 claims description 3
- 239000010703 silicon Substances 0.000 claims description 3
- 238000003780 insertion Methods 0.000 abstract description 8
- 230000037431 insertion Effects 0.000 abstract description 8
- 230000007547 defect Effects 0.000 abstract description 5
- 239000000463 material Substances 0.000 description 5
- 238000004891 communication Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000010295 mobile communication Methods 0.000 description 2
- 230000003071 parasitic effect Effects 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
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- 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
-
- 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
-
- 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
- H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material
-
- 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
- H03H2003/023—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 the resonators or networks being of the membrane type
-
- 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
- H03H2003/028—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 values of other parameters
-
- 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
- H03H2003/0414—Resonance frequency
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
Abstract
A method for improving the performance of an FBAR filter belongs to the technical field of filter preparation. The method comprises the following steps: 1) preparing an FBAR filter; 2) the FBAR filter is placed in an annealing furnace, and nitrogen is introduced into the annealing furnace to keep the partial pressure of the nitrogen above 99%; 3) and (3) raising the temperature in the annealing furnace from room temperature to 400 ℃ at a heating rate of 2-6 ℃/min, preserving the heat at 400 ℃ for 20-60 min, reducing the temperature from 400 ℃ to room temperature at a cooling rate of 2-6 ℃/min, and taking out. According to the invention, the whole FBAR filter obtained by preparation is subjected to annealing treatment, so that each layer of film is combined more tightly, the defects at the film junction are reduced, and the problem of energy loss caused by diffuse reflection of sound waves at the film interface is solved; meanwhile, the center frequency, the 3dB bandwidth, the relative bandwidth, the insertion loss and the rectangular coefficient of the filter are all improved to a certain degree.
Description
Technical Field
The invention belongs to the technical field of filter preparation, and particularly relates to a method for improving the performance of an FBAR filter.
Background
An FBAR (Film bulk Acoustic wave filter) filter is a novel radio frequency filter, and is composed of Acoustic wave resonators, the principle of which is based on the piezoelectric effect, and a piezoelectric Film and upper and lower electrode films jointly form a transducer, so that the performance and the crystallization quality of the piezoelectric Film also determine the final performance of the filter. The frequency of the resonator is determined by the velocity of the electromagnetic or acoustic wave propagating in the cavity and the size of the cavity, which is proportional to the wave velocity. The wave velocity of the electromagnetic wave is 3 x 108m/s, the sound velocity of sound wave is 3000-11000 m/s, compared with the traditional cavity and dielectric filter which work by utilizing electromagnetic wave, the size absolute advantage is achieved, and the method is the best choice for the filter at the mobile communication end at present. The acoustic filter has the advantages of high Q value, high frequency, high reliability, small volume and batch manufacture, and is widely applied to the fields of base stations, automotive electronics, navigation, radar, communication, electronic countermeasure and the like.
With the continuous development of mobile communication technology, communication spectrum resources are increasingly tense, and the protection frequency band is increasingly narrowed. The arrival of 5G communication technology will further increase the communication frequency band, and at the same time, the operating bandwidth will also increase. New application scenarios bring new requirements for filters, and high frequency and wide bandwidth will be the inevitable trend of filter development in the future. At present, the method for improving the overall performance of the FBAR filter is mainly to replace piezoelectric layer and electrode layer film materials, but is limited by the limited electromechanical coupling coefficient of piezoelectric materials, the limited resistivity and acoustic impedance of electrode materials and the like, and the consideration on material cost, and the selection range and the promotion space for optimizing the performance of the FBAR filter by changing the used materials are extremely limited. Therefore, on the premise of not changing materials, a new convenient, quick and low-cost method for optimizing the performance of the filter is urgently needed.
Disclosure of Invention
The invention aims to provide a method for improving the performance of an FBAR filter aiming at the defects in the prior art.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method of improving the performance of an FBAR filter comprising the steps of:
step 1, preparation of an FBAR filter:
digging a groove on a high-resistance silicon wafer with the resistivity of more than 5000 omega cm, sequentially depositing a sacrificial layer, a seed layer, a lower electrode layer, a piezoelectric layer, an upper electrode layer, a frequency modulation layer and a pad layer in the groove, and carrying out photoetching and patterning to obtain the FBAR filter;
step 2, setting an annealing environment:
putting the FBAR filter prepared in the step 1 into an annealing furnace, and introducing nitrogen into the annealing furnace to keep the partial pressure of the nitrogen above 99%, thereby effectively avoiding O2The presence of (a) causes the metal electrodes of the FBAR filter to be oxidized at high temperatures resulting in increased insertion loss;
step 3, annealing temperature rise stage:
the temperature in the annealing furnace is increased from room temperature to 400 ℃ at the heating rate of 2-6 ℃/min, and the film collapse or film fracture at the cavity of the FBAR filter is effectively avoided at the heating rate;
step 4, annealing heat preservation stage:
setting the annealing heat preservation temperature to be 400 ℃ and setting the heat preservation time to be 20-60 min; at this temperature, defects at the interface of each layer of the film of the FBAR filter are obviously reduced, the diffuse reflection of sound waves at the interface is reduced, and the transverse parasitic vibration of the filter is reduced. Meanwhile, the temperature can also effectively avoid the increase of insertion loss caused by the blackening of the bonding pad Al at high temperature;
step 5, annealing cooling stage:
reducing the temperature in the annealing furnace from 400 ℃ to room temperature at a cooling rate of 2-6 ℃/min, and taking out to obtain a treated FBAR filter; through the control to the cooling rate, the film that has effectively avoided FBAR filter cavity department to appear collapses or the film breaks.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the method for improving the performance of the FBAR filter, the prepared FBAR filter is subjected to annealing treatment, so that the films of all layers are combined more tightly, the defects at the film junction are reduced, and the problem of energy loss caused by diffuse reflection of sound waves at the film interface is solved.
2. According to the method for improving the performance of the FBAR filter, the prepared FBAR filter is annealed, the center frequency of the annealed FBAR filter is increased from 3238MHz to 3250MHz, and the center frequency is increased by 22 MHz; the 3dB bandwidth is improved from 231.1MHz to 261.3MHz, and 29.8MHz is increased; the relative bandwidth is improved from 7.1% to 8.1%; the insertion loss is changed from-2.66 dB to-2.4 dB, and the insertion loss is reduced by 0.26 dB; the rectangular coefficient is reduced from 1.848 to 1.648, and the performance is improved to a certain extent in all aspects.
Drawings
FIG. 1 is a graph of S-parameters of an FBAR filter prepared in step 1 (before annealing) and an FBAR filter annealed in step 5 (after annealing) of the example;
fig. 2 is a flowchart of a method for improving the performance of an FBAR filter according to the present invention.
Detailed Description
The technical scheme of the invention is detailed below by combining the accompanying drawings and the embodiment.
Examples
Step 1, preparation of an FBAR filter:
digging a groove on a high-resistance silicon wafer with the resistivity of more than 5000 omega cm, sequentially depositing a sacrificial layer, a seed layer, a lower electrode layer, a piezoelectric layer, an upper electrode layer, a frequency modulation layer and a pad layer in the groove, and carrying out photoetching and patterning to obtain the FBAR filter; the seed layer and the frequency modulation layer are made of AlN, the piezoelectric layer is made of ScAlN, and the electrode layer is made of Mo;
step 2, setting an annealing environment:
putting the FBAR filter prepared in the step 1 into an annealing furnace, and introducing nitrogen into the annealing furnaceGas, the partial pressure of nitrogen is kept above 99 percent, and O is effectively avoided2The presence of (a) causes the metal electrodes of the FBAR filter to be oxidized at high temperatures resulting in increased insertion loss;
step 3, annealing temperature rise stage:
the temperature in the annealing furnace is increased from room temperature to 400 ℃ at the heating rate of 4 ℃/min, and the film collapse or film fracture at the cavity of the FBAR filter is effectively avoided at the heating rate;
step 4, annealing heat preservation stage:
setting the annealing heat preservation temperature to 400 ℃ and the heat preservation time to 30 min; at the temperature, the films of the FBAR filter are combined more tightly, defects existing at the junction can be obviously reduced, diffuse reflection of sound waves generated at the interface is reduced, and transverse parasitic vibration of the filter is reduced. Meanwhile, the temperature can also effectively avoid the increase of insertion loss caused by the blackening of the bonding pad aluminum at high temperature;
step 5, annealing cooling stage:
reducing the temperature in the annealing furnace from 400 ℃ to room temperature at a cooling rate of 4 ℃/min, and taking out to obtain the processed FBAR filter; through the control to the cooling rate, the film that has effectively avoided FBAR filter cavity department to appear sinks or the film breaks.
FIG. 1 is a graph of S-parameters of an FBAR filter prepared in step 1 (before annealing) and an FBAR filter annealed in step 5 (after annealing) of the example; as can be seen from FIG. 1, the center frequency of the FBAR filter after annealing treatment is increased from 3238MHz to 3250MHz, and is increased by 22 MHz; the 3dB bandwidth is improved from 231.1MHz to 261.3MHz, and 29.8MHz is increased; the relative bandwidth is improved from 7.1% to 8.1%; the insertion loss is changed from-2.66 dB to-2.4 dB, and is reduced by 0.26 dB; the rectangular coefficient is reduced from 1.848 to 1.648, and the performance is improved comprehensively.
Claims (1)
1. A method for improving the performance of an FBAR filter, comprising the steps of:
step 1, preparation of an FBAR filter:
digging a groove on the high-resistance silicon chip, sequentially depositing a sacrificial layer, a seed layer, a lower electrode layer, a piezoelectric layer, an upper electrode layer, a frequency modulation layer and a pad layer in the groove, and carrying out photoetching and patterning to obtain the FBAR filter;
step 2, setting an annealing environment:
putting the FBAR filter prepared in the step 1 into an annealing furnace, and introducing nitrogen into the annealing furnace to keep the partial pressure of the nitrogen above 99%;
step 3, annealing temperature rise stage:
heating the temperature in the annealing furnace from room temperature to 400 ℃ at a heating rate of 2-6 ℃/min;
step 4, annealing heat preservation stage:
setting the annealing heat preservation temperature to be 400 ℃ and setting the heat preservation time to be 20-60 min;
step 5, annealing cooling stage:
and (3) reducing the temperature in the annealing furnace from 400 ℃ to room temperature at a cooling rate of 2-6 ℃/min, and taking out to obtain the treated FBAR filter.
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| CN202210305141.9A CN114640320A (en) | 2022-03-25 | 2022-03-25 | Method for improving performance of FBAR filter |
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| CN202210305141.9A CN114640320A (en) | 2022-03-25 | 2022-03-25 | Method for improving performance of FBAR filter |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110137341A (en) * | 2018-02-02 | 2019-08-16 | 中国科学院上海微系统与信息技术研究所 | The preparation method of single-crystal piezoelectric film foreign substrate |
| CN110729979A (en) * | 2019-09-30 | 2020-01-24 | 中国电子科技集团公司第二十六研究所 | Wafer-level packaging method and structure of film bulk acoustic wave filter |
| CN112039481A (en) * | 2019-08-09 | 2020-12-04 | 中芯集成电路（宁波）有限公司 | Bulk acoustic wave resonator and method for manufacturing the same |
| CN112217493A (en) * | 2019-07-10 | 2021-01-12 | 开元通信技术（厦门）有限公司 | Bulk acoustic wave filter and method for manufacturing the same |
| CN113810018A (en) * | 2021-08-30 | 2021-12-17 | 浙江大学杭州国际科创中心 | Method for preparing single crystal film bulk acoustic resonator in laser lift-off mode |
-
2022
- 2022-03-25 CN CN202210305141.9A patent/CN114640320A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110137341A (en) * | 2018-02-02 | 2019-08-16 | 中国科学院上海微系统与信息技术研究所 | The preparation method of single-crystal piezoelectric film foreign substrate |
| CN112217493A (en) * | 2019-07-10 | 2021-01-12 | 开元通信技术（厦门）有限公司 | Bulk acoustic wave filter and method for manufacturing the same |
| CN112039481A (en) * | 2019-08-09 | 2020-12-04 | 中芯集成电路（宁波）有限公司 | Bulk acoustic wave resonator and method for manufacturing the same |
| CN110729979A (en) * | 2019-09-30 | 2020-01-24 | 中国电子科技集团公司第二十六研究所 | Wafer-level packaging method and structure of film bulk acoustic wave filter |
| CN113810018A (en) * | 2021-08-30 | 2021-12-17 | 浙江大学杭州国际科创中心 | Method for preparing single crystal film bulk acoustic resonator in laser lift-off mode |
Non-Patent Citations (1)
| Title |
|---|
| 陈香玉: "固态装配型FBAR器件制备及其可调谐BST薄膜掺杂改性研究", 《中国优秀博硕士学位论文全文数据库(硕士)工程科技Ⅱ辑》, no. 11, pages 30 - 37 * |
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