CN115694388A - Bulk acoustic wave filter and manufacturing method thereof - Google Patents
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- H—ELECTRICITY
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- 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
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/02—Details
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Abstract
The invention relates to a bulk acoustic wave filter and a manufacturing method thereof. The method for manufacturing the bulk acoustic wave filter comprises the following steps: determining the design thickness of the corresponding piezoelectric layers according to the design frequencies of the 1 st resonator to the nth resonator, wherein n is more than or equal to 2; forming air cavities of a 1 st resonator to an nth resonator, a sacrificial layer, a seed layer, a bottom electrode layer and a piezoelectric layer with the thickness of T on a wafer substrate; trimming the thickness of the piezoelectric layers of the 1 st to nth resonators to a designed thickness by adopting Ar + ion beams to form the piezoelectric layers of the 1 st to nth resonators with different thicknesses; forming a top electrode layer on the trimmed 1 st to nth resonator piezoelectric layers; and releasing the sacrificial layer to obtain the bulk acoustic wave filter. The manufacturing method of the bulk acoustic wave filter can manufacture filters with different frequencies on the same wafer, and can greatly reduce the area of a chip when the filters with different frequencies are integrated.
Description
Technical Field
The invention relates to the technical field of filters, in particular to a bulk acoustic wave filter and a manufacturing method thereof.
Background
The acoustic resonator converts an electric signal into a vibration (sound) signal using an inverse piezoelectric effect, and outputs only the signal by resonating vibration (sound) of a specific frequency due to the characteristics of the resonator itself. Acoustic resonators typically include Surface Acoustic Wave (SAW) resonators, bulk Acoustic Wave (BAW) resonators, and the like.
Bulk Acoustic Wave (BAW) resonators, which are made by longitudinal resonance of piezoelectric thin films in the thickness direction, have become indispensable radio frequency devices in the field of high frequency mobile communications. Bulk acoustic wave filters/duplexers offer superior filtering characteristics such as low insertion loss, steep transition band, large power capacity, strong anti-electrostatic discharge (ESD) capability. In addition, bulk Acoustic Wave (BAW) resonator processing is compatible with CMOS processes, which also facilitates final integration with circuitry.
However, due to the size limitation of the interdigital electrode, the SAW resonator is difficult to break through the upper limit of the frequency of 3GHz, and the SAW resonator is limited in the application of the high-frequency band of Sub-6G; the common FBAR in the BAW resonator has higher defect density of a polycrystalline AlN film, poorer crystal quality and influenced performance, and meanwhile, the yield of devices is correspondingly reduced due to the damage of the sacrificial layer release and the CMP process to the resonator; different resonant frequencies on different resonators are obtained, the thickness of a piezoelectric film is generally controlled in the prior art, and since an electrode material film is generally prepared on a whole wafer through sputtering equipment, the piezoelectric film with the same thickness is mostly adopted in the resonators manufactured on the same wafer at present; in order not to increase the process complexity, the filter manufacturing process usually adjusts the total thickness of the resonator region by changing the mass loading layer on different resonators to obtain resonators with different resonant frequencies, so as to form a multistage filter by cascading.
However, forming the mass load from the electrode material increases the thickness of the electrode, which has a negative effect on the effective electromechanical coupling coefficient of the resonator itself, and thus the frequency tuning range is low. When meeting the integrated demand of duplexer and radio frequency front end, when needing the wave filter of multiple frequency, often need earlier the discrete device of wave filter preparation, integrate again after preliminary encapsulation, be unfavorable for the reduction of whole module area.
Therefore, on the basis of improving the crystal quality, reducing the device damage and further improving the performance and yield of the resonator, how to accurately control the frequency of the resonator/filter and reduce the total area of the integrated module part becomes a problem to be solved urgently.
Disclosure of Invention
Based on the above, the invention provides a method for manufacturing a bulk acoustic wave filter, which can manufacture filters with different frequencies on the same wafer, and can greatly reduce the area of a chip when the filters with different frequencies are integrated; if the common ground design method of the filter is combined, the ground wires can be shared among the filters, the integrated chip area of the filter is further reduced, and the chip yield on one wafer is improved. Meanwhile, because the filters with different frequencies required by the integrated chip can be integrated together, the integral packaging of the filters with different frequencies can be realized, and the form of integrated packaging after packaging of discrete devices is not needed, thereby saving packaging materials and reducing packaging cost.
A method for manufacturing a bulk acoustic wave filter comprises the following steps:
determining the design thickness of the corresponding piezoelectric layers according to the design frequencies of the 1 st resonator to the nth resonator, wherein n is more than or equal to 2;
forming an air cavity, a sacrificial layer, a seed layer, a bottom electrode layer and a piezoelectric layer with the thickness of T on a wafer substrate, wherein T is larger than or equal to the design thickness of any piezoelectric layer pressed by the 1 st resonator to the nth resonator;
trimming the thickness of the piezoelectric layers of the 1 st to nth resonators to a designed thickness by adopting Ar + ion beams to form the piezoelectric layers of the 1 st to nth resonators with different thicknesses;
forming a top electrode layer on the trimmed 1 st to nth resonator piezoelectric layers;
and releasing the sacrificial layer to obtain the bulk acoustic wave filter.
The invention obtains various resonators with different resonant frequencies by forming piezoelectric layers with different thicknesses on the same wafer, thereby reducing the electrode thickness of the bulk acoustic wave resonator, increasing the effective electromechanical coupling coefficient (kt 2 eff) of the resonator, reducing the reserved slice interval between filters with different frequencies, obviously reducing the area of the filter and greatly reducing the area of an integrated module. The piezoelectric layer is trimmed by Ar + ion beams, so that the thickness and uniformity of the piezoelectric film can be accurately controlled, the whole manufacturing time is short, and the efficiency is high.
Further, the step of trimming the thickness of the piezoelectric layer by using Ar + ion beams comprises the following steps:
taking N from 1 to N, and respectively repeating the following processes:
taking an Nth shielding plate, and making an alignment mark or an alignment mark area at the fixed position of the shielding plate and the wafer substrate, wherein the shielding plate completely covers the wafer substrate;
forming a hole in an orthographic projection area corresponding to the nth resonator voltage layer on the nth shielding plate;
aligning and fixing the Nth shielding plate with the wafer substrate, bombarding by adopting Ar + ion beams, and trimming the piezoelectric layer of the Nth resonator to the designed thickness;
the shielding plate is made of an Ar + ion beam etching resistant material.
And the shielding plate is adopted to shield the part which does not need to be trimmed, so that the Ar + ion beam can be used for accurately positioning and trimming the piezoelectric layer, and the positioning control requirement on the Ar + ion beam is reduced. The shielding plate is provided with a hole in the area needing to be trimmed, the Ar + ion beam can pass through the shielding plate without being influenced, and the other positions form a barrier for the Ar + ion beam, so that the bombardment of the ion beam on the material below only exists in a specific position.
Further, trimming the thickness of the piezoelectric layer with an Ar + ion beam comprises the steps of:
taking a shielding plate, and making an alignment mark or an alignment mark area at the fixed position of the shielding plate and the wafer substrate, wherein the shielding plate completely covers the wafer substrate;
respectively forming holes in orthographic projection areas corresponding to the voltage layers of the 1 st resonator to the nth resonator on the shielding plate;
aligning and fixing the shielding plate with the wafer substrate by Ar + Bombarding voltage layers of the 1 st resonator to the nth resonator one by using ion beams, and trimming piezoelectric layers of the 1 st resonator to the nth resonator to a designed thickness;
the shielding plate is made of a material resistant to Ar + ion beam etching.
And the shielding plate is adopted to shield the part which does not need to be trimmed, so that the Ar + ion beams can be used for accurately positioning and trimming the piezoelectric layer, and the positioning control requirement on the Ar + ion beams is reduced. The area on the baffle plate needing to be trimmed is provided with a hole, ar + ion beams can pass through the hole without being influenced, and the rest positions form the block to the Ar + ion beams, so that the bombardment of the ion beams to the materials below only exists at specific positions.
Further, before Ar + ion beam bombardment, the method also comprises the following steps: measuring the actual thickness of the piezoelectric layer, calculating the trimming thickness, wherein the trimming thickness = actual thickness-design thickness, and controlling the intensity of Ar + ion beams and the bombardment duration to thin the piezoelectric layer by the trimming thickness to obtain the piezoelectric layer with the corresponding design thickness.
Trimming is carried out according to the actual thickness of the piezoelectric layer to improve the trimming precision, and the intensity of the Ar + ion beam and the bombardment duration are controlled by a computer according to the actual trimming thickness.
Furthermore, the shielding plate is made of one or more of Pt, ceramic materials, siC and SiO2, the shielding plate can obviously block the etching effect of Ar + ion beams, and the part of the shielding plate damaged by etching in the using process can be supplemented in a coating mode, so that the shielding plate can be repeatedly used.
Further, when the piezoelectric layer is trimmed by Ar + ion beams, the environmental vacuum degree is not lower than 10 -7 And (5) Torr. And (3) bombarding the film by using high-energy Ar gas to realize finishing, wherein the high-energy Ar gas is required to collide with residual gas molecules in the cavity in a high-vacuum environment.
Further, a specific method for forming the air cavity, the sacrificial layer, the seed layer, the bottom electrode layer and the piezoelectric layer of the 1 st resonator to the nth resonator comprises the following steps:
cleaning the wafer substrate, and forming an air cavity on the wafer substrate;
forming a sacrificial layer on a wafer substrate, and enabling the upper surface of the sacrificial layer to be flush with the upper surface of the substrate by adopting a CMP (chemical mechanical polishing) process;
forming a seed layer film and a bottom electrode layer film on the upper surfaces of the wafer substrate and the sacrificial layer in sequence, and carrying out photoetching and etching processes on the seed layer film and the bottom electrode layer film to form a bottom electrode pattern, wherein the bottom electrode pattern covers the air cavity part and exposes the sacrificial layer release channel;
and forming a piezoelectric layer film on the upper surfaces of the wafer substrate, the sacrificial layer and the bottom electrode layer, and removing the piezoelectric layer film outside the upper surface of the bottom electrode layer by photoetching and etching the piezoelectric layer film to obtain the piezoelectric layer.
Further, forming the acoustic reflection air cavity by adopting photoetching, dry etching or wet etching process;
forming the sacrificial layer by adopting sputtering, chemical vapor deposition, physical vapor deposition or spin coating process;
and forming the seed layer and the bottom electrode layer by adopting a sputtering process.
Further, the sacrificial layer material comprises phosphorous doped silicon oxide, metal or polymer; the seed layer material is AlN; the bottom electrode layer is made of one of Mo, al and Cu; the piezoelectric layer is AlN with a preferred c-axis orientation.
The invention also provides a bulk acoustic wave filter which is manufactured by the manufacturing method.
For a better understanding and practice, the invention is described in detail below with reference to the accompanying drawings.
Drawings
Fig. 1 is a schematic structural diagram of a wafer substrate with a cavity formed thereon according to an embodiment.
Fig. 2 is a schematic structural diagram after forming a sacrificial layer according to an embodiment.
Fig. 3 is a schematic structural diagram of forming a seed layer and a bottom electrode layer and performing patterning according to the first embodiment.
Fig. 4 is a schematic structural diagram after forming a piezoelectric layer according to the first embodiment.
Fig. 5 is a schematic structural diagram of trimming a piezoelectric layer of a resonator by using an Ar + ion beam and a shielding plate according to an embodiment.
Fig. 6 is a schematic structural diagram of trimming another resonator piezoelectric layer by using an Ar + ion beam and a shielding plate according to an embodiment.
Fig. 7 is a schematic structural diagram of a bulk acoustic wave filter according to an embodiment.
Detailed Description
The present invention will be described in further detail below with reference to specific embodiments and with reference to the attached drawings.
Example 1
The embodiment provides a bulk acoustic wave filter and a manufacturing method thereof.
Referring to fig. 1 to 7, the method for manufacturing the bulk acoustic wave filter includes the steps of:
and step 01, determining the design thickness of the corresponding piezoelectric layers according to the design frequencies of the 1 st resonator to the nth resonator, wherein n is more than or equal to 2.
Referring to fig. 1, a wafer substrate 1 is cleaned and the air cavities 2 of the various resonators 101-1, 101-2, … 101-n of the filter 101 are formed on the wafer substrate 1. Specifically, the air cavity 2 may be formed by photolithography, a dry etching process, or a wet etching process.
Step 02, forming a sacrificial layer on the wafer substrate 1, wherein the air cavity 2 is completely filled with the sacrificial layer. Wherein the sacrificial layer is made of phosphorus-doped silicon oxide (PSG) and is prepared by a Chemical Vapor Deposition (CVD) process.
And step 03, referring to fig. 2, polishing the surface of the substrate by using a CMP process, and removing the sacrificial layer protruding above the plane of the wafer substrate 1, so that the upper surface of the sacrificial layer is flush with the upper surface of the substrate.
Step 04, referring to fig. 3, a seed layer film is formed on the upper surface of the wafer substrate 1, and a bottom electrode layer film is formed on the upper surface of the seed layer film. And photoetching and etching the seed layer film and the bottom electrode layer film to form a bottom electrode pattern, so as to obtain the seed layer 3 and the bottom electrode layer 4, and expose the sacrificial layer release channel 9. The seed layer material can be AlN, and the bottom electrode layer material can be one of Mo, al and Cu.
And step 05, forming piezoelectric layer films on the upper surfaces of the wafer substrate 1, the sacrificial layer 2 and the bottom electrode layer 4, and performing photoetching and etching processes on the piezoelectric layer films to remove part of the piezoelectric layer films except the upper surface of the bottom electrode layer to obtain the piezoelectric layer 5. In an embodiment, the piezoelectric layer is c-axis preferentially oriented AlN grown by magnetron sputtering.
Step 06, determining the design thickness of the corresponding piezoelectric layers according to the design frequencies of the 1 st resonator to the nth resonator; by Ar + The ion beam trims the thickness of the piezoelectric layers of the 1 st to nth resonators to a design thickness:
taking N from 1 to N, and respectively repeating the following processes:
taking an Nth shielding plate, and making an alignment mark or an alignment mark area at the fixed position of the shielding plate and the wafer substrate, wherein the shielding plate can completely cover the wafer substrate;
forming a hole in an orthographic projection area corresponding to the nth resonator voltage layer on the nth shielding plate;
measuring the actual thickness of the piezoelectric layer, and calculating a trimming thickness, wherein the trimming thickness = the actual thickness-a design thickness;
aligning and fixing an Nth shielding plate with a wafer substrate (the shielding plate is fixed on the wafer substrate or on equipment), bombarding by adopting Ar + ion beams 7, trimming a piezoelectric layer of an Nth resonator, reducing the trimming thickness, and when trimming is carried out, ensuring that the environmental vacuum degree is not lower than 10 -7 Torr；
The shielding plate adopts Pt, ceramic material, siC and SiO which resist Ar + ion beam etching 2 Any one of the materials.
Referring to fig. 5, the piezoelectric layer of resonator 101-2 is trimmed using shutter 6-2 and Ar + ion beam 7.
Referring to FIG. 6, the piezoelectric layer of resonator 101-n is trimmed using shadow mask 6-n and Ar + ion beam 7.
In other embodiments, the piezoelectric layers of the 1 st to nth resonators may be trimmed with only one shielding plate, specifically:
taking a shielding plate, and making an alignment mark or an alignment mark area at the fixed position of the shielding plate and the wafer substrate, wherein the shielding plate completely covers the wafer substrate;
respectively forming holes in orthographic projection areas corresponding to the voltage layers of the 1 st resonator to the nth resonator on the shielding plate;
aligning and fixing the shielding plate and the wafer substrate, bombarding the voltage layers from the 1 st resonator to the nth resonator one by adopting Ar + ion beams, trimming the piezoelectric layers of the 1 st resonator to the nth resonator, and thinning the trimming thickness.
Step 07, referring to fig. 7, a top electrode layer 8 is sputtered on the piezoelectric layer 5, a required pattern is formed through photolithography and etching processes, a sandwich structure is formed, and then the sacrificial layer is released through a sacrificial layer release channel 9 to form a cavity, so that filters with different frequencies can be manufactured on the same wafer.
The invention also provides a bulk acoustic wave filter which is manufactured by the manufacturing method.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is specific and detailed, but not to be understood as limiting the scope of the invention. It should be noted that, to those skilled in the art, changes and modifications may be made without departing from the spirit of the present invention, and it is intended that the present invention encompass such changes and modifications.
Claims (10)
1. A method for manufacturing a bulk acoustic wave filter is characterized by comprising the following steps:
determining the design thickness of the corresponding piezoelectric layers according to the design frequencies of the 1 st resonator to the nth resonator, wherein n is more than or equal to 2;
forming air cavities of a 1 st resonator to an nth resonator, a sacrificial layer, a seed layer, a bottom electrode layer and a piezoelectric layer with the thickness of T on a wafer substrate, wherein the thickness of T is more than or equal to the design thickness of any piezoelectric layer pressed by the 1 st resonator to the nth resonator;
determining the thickness of the corresponding piezoelectric layer according to the design frequencies of the 1 st resonator to the nth resonator;
by Ar + The ion beam trims the thickness of the piezoelectric layers of the 1 st to nth resonators to a designed thickness to form the piezoelectric layers of the 1 st to nth resonators with different thicknesses;
forming a top electrode layer on the trimmed 1 st to nth resonator piezoelectric layers;
and releasing the sacrificial layer to obtain the bulk acoustic wave filter.
2. The method of manufacturing a bulk acoustic wave filter according to claim 1, wherein the step of forming the filter is performed by a method of manufacturing a bulk acoustic wave filter: by Ar + Ion beam trimming piezoelectric layer thickness includes the steps of:
taking N from 1 to N, and respectively repeating the following processes:
taking an Nth shielding plate, and making an alignment mark or an alignment mark area at the fixed position of the shielding plate and the wafer substrate, wherein the shielding plate can completely cover the wafer substrate;
forming a hole in an orthographic projection area corresponding to the nth resonator voltage layer on the nth shielding plate;
aligning and fixing the Nth shielding plate with the wafer substrate by Ar + Bombarding by using an ion beam, and trimming the piezoelectric layer of the Nth resonator to a designed thickness;
the shielding plate is made of an Ar + ion beam etching resistant material.
3. The method of manufacturing a bulk acoustic wave filter according to claim 1, characterized in that: by Ar + Ion beam trimming piezoelectric layer thickness includes the steps of:
taking a shielding plate, and making an alignment mark or an alignment mark area at the fixed position of the shielding plate and the wafer substrate, wherein the shielding plate can completely cover the wafer substrate;
respectively forming holes in orthographic projection areas corresponding to voltage layers of the 1 st resonator to the nth resonator on the shielding plate;
aligning and fixing the shielding plate with the wafer substrate by Ar + Bombarding voltage layers of the 1 st resonator to the nth resonator one by ion beams, and trimming piezoelectric layers of the 1 st resonator to the nth resonator to a designed thickness;
the shielding plate is made of a material resistant to Ar + ion beam etching.
4. The method of manufacturing a bulk acoustic wave filter according to claim 2 or 3, characterized in that: carrying out Ar + The ion beam bombardment also comprises: measuring the actual thickness of the piezoelectric layer, calculating a trimming thickness, wherein the trimming thickness = actual thickness-design thickness, and controlling Ar + Ion beam intensity and bombardment duration to thin the piezoelectric layer by the trimming thickness to obtain corresponding designA thickness of the piezoelectric layer.
5. The method of manufacturing a bulk acoustic wave filter according to claim 2 or 3, characterized in that: the shielding plate is made of Pt, ceramic material, siC and SiO 2 One or more of them are compounded.
6. The method of manufacturing a bulk acoustic wave filter according to claim 1, wherein: by Ar + When the ion beam trims the piezoelectric layer, the environmental vacuum degree is not less than 10 -7 Torr。
7. The method of manufacturing a bulk acoustic wave filter according to claim 1, characterized in that: the specific method for forming the air cavity, the sacrificial layer, the seed layer, the bottom electrode layer and the piezoelectric layer of the 1 st resonator to the nth resonator comprises the following steps:
cleaning the wafer substrate, and forming an air cavity on the wafer substrate;
forming a sacrificial layer on a wafer substrate, and enabling the upper surface of the sacrificial layer to be flush with the upper surface of the substrate by adopting a CMP (chemical mechanical polishing) process;
sequentially forming a seed layer film and a bottom electrode layer film on the upper surfaces of the wafer substrate and the sacrificial layer, carrying out photoetching and etching processes on the seed layer film and the bottom electrode layer film to form a bottom electrode pattern, and exposing a sacrificial layer release channel;
and forming a piezoelectric layer film on the upper surfaces of the wafer substrate, the sacrificial layer and the bottom electrode layer, and removing the piezoelectric layer film outside the upper surface of the bottom electrode layer by photoetching and etching the piezoelectric layer film to obtain the piezoelectric layer.
8. The method of manufacturing a bulk acoustic wave filter according to claim 5, wherein:
forming the air cavity by adopting photoetching, dry etching or wet etching process;
forming the sacrificial layer by adopting sputtering, chemical vapor deposition, physical vapor deposition or spin coating process;
and forming the seed layer and the bottom electrode layer by adopting a sputtering process.
9. The method of manufacturing a bulk acoustic wave filter according to claim 5, characterized in that: the sacrificial layer material comprises phosphorus-doped silicon oxide, metal or polymer; the seed layer material is AlN; the bottom electrode layer is made of one of Mo, al and Cu; the piezoelectric layer is AlN with a preferred c-axis orientation.
10. A bulk acoustic wave filter, characterized by: manufactured by the manufacturing method according to any one of claims 1 to 9.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211317441.5A CN115694388A (en) | 2022-10-26 | 2022-10-26 | Bulk acoustic wave filter and manufacturing method thereof |
| PCT/CN2023/071393 WO2024087400A1 (en) | 2022-10-26 | 2023-01-09 | Bulk acoustic wave filter and manufacturing method therefor |
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| CN202211317441.5A CN115694388A (en) | 2022-10-26 | 2022-10-26 | Bulk acoustic wave filter and manufacturing method thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117938106A (en) * | 2024-03-14 | 2024-04-26 | 深圳新声半导体有限公司 | Integrated bulk acoustic wave filter and manufacturing method |
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| 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 |
| US11245383B2 (en) * | 2019-07-25 | 2022-02-08 | Zhuhai Crystal Resonance Technologies Co., Ltd. | Packages with organic back ends for electronic components |
| CN111262548B (en) * | 2019-12-31 | 2021-06-22 | 诺思(天津)微系统有限责任公司 | Bulk acoustic wave resonator group, filter, electronic device, and electromechanical coupling coefficient adjustment method |
| CN111817678B (en) * | 2020-07-03 | 2021-12-28 | 中国科学院上海微系统与信息技术研究所 | Monolithic hybrid integrated acoustic resonator array and preparation method thereof |
| CN115242202A (en) * | 2022-06-17 | 2022-10-25 | 杭州左蓝微电子技术有限公司 | Preparation process of film bulk acoustic resonator and film bulk acoustic resonator |
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| CN117938106A (en) * | 2024-03-14 | 2024-04-26 | 深圳新声半导体有限公司 | Integrated bulk acoustic wave filter and manufacturing method |
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