CN117375572A - Film bulk acoustic wave filter with concave-convex temperature compensation layer structure and preparation method thereof - Google Patents
Film bulk acoustic wave filter with concave-convex temperature compensation layer structure and preparation method thereof Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title claims abstract description 7
- 239000010410 layer Substances 0.000 claims abstract description 175
- 239000011241 protective layer Substances 0.000 claims abstract description 31
- 239000000758 substrate Substances 0.000 claims abstract description 25
- 239000010408 film Substances 0.000 claims description 71
- 239000010409 thin film Substances 0.000 claims description 14
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 claims description 13
- 238000005530 etching Methods 0.000 claims description 13
- 239000000463 material Substances 0.000 claims description 13
- 239000011248 coating agent Substances 0.000 claims description 12
- 238000000576 coating method Methods 0.000 claims description 12
- 238000001755 magnetron sputter deposition Methods 0.000 claims description 12
- 238000001259 photo etching Methods 0.000 claims description 11
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical group O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 claims description 5
- 235000012239 silicon dioxide Nutrition 0.000 claims description 5
- 239000000377 silicon dioxide Substances 0.000 claims description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 4
- GQPLMRYTRLFLPF-UHFFFAOYSA-N Nitrous Oxide Chemical compound [O-][N+]#N GQPLMRYTRLFLPF-UHFFFAOYSA-N 0.000 claims description 4
- 238000005229 chemical vapour deposition Methods 0.000 claims description 3
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims description 2
- 229910052786 argon Inorganic materials 0.000 claims description 2
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- 239000001272 nitrous oxide Substances 0.000 claims description 2
- 229910000077 silane Inorganic materials 0.000 claims description 2
- 238000000059 patterning Methods 0.000 claims 1
- 230000002829 reductive effect Effects 0.000 abstract description 18
- 238000000034 method Methods 0.000 abstract description 17
- 230000008569 process Effects 0.000 abstract description 12
- 230000003247 decreasing effect Effects 0.000 abstract description 5
- 230000000694 effects Effects 0.000 abstract description 4
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 12
- 230000008719 thickening Effects 0.000 description 5
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 229910052741 iridium Inorganic materials 0.000 description 4
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 4
- 229910052697 platinum Inorganic materials 0.000 description 4
- 229910052707 ruthenium Inorganic materials 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 4
- 229910052721 tungsten Inorganic materials 0.000 description 4
- 239000010937 tungsten Substances 0.000 description 4
- 229910004298 SiO 2 Inorganic materials 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- PIGFYZPCRLYGLF-UHFFFAOYSA-N Aluminum nitride Chemical compound [Al]#N PIGFYZPCRLYGLF-UHFFFAOYSA-N 0.000 description 2
- 229910001182 Mo alloy Inorganic materials 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 2
- 229910052581 Si3N4 Inorganic materials 0.000 description 2
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000670 limiting effect Effects 0.000 description 2
- 239000011572 manganese Substances 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 239000011733 molybdenum Substances 0.000 description 2
- 229910052761 rare earth metal Inorganic materials 0.000 description 2
- 150000002910 rare earth metals Chemical class 0.000 description 2
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 2
- 230000001629 suppression Effects 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- 150000003624 transition metals Chemical class 0.000 description 2
- 229910052691 Erbium Inorganic materials 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 238000004891 communication Methods 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
- 230000007547 defect Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 238000004049 embossing Methods 0.000 description 1
- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910052735 hafnium Inorganic materials 0.000 description 1
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- HFGPZNIAWCZYJU-UHFFFAOYSA-N lead zirconate titanate Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ti+4].[Zr+4].[Pb+2] HFGPZNIAWCZYJU-UHFFFAOYSA-N 0.000 description 1
- 229910052451 lead zirconate titanate Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 238000010295 mobile communication Methods 0.000 description 1
- 230000036961 partial effect Effects 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 description 1
- VSZWPYCFIRKVQL-UHFFFAOYSA-N selanylidenegallium;selenium Chemical compound [Se].[Se]=[Ga].[Se]=[Ga] VSZWPYCFIRKVQL-UHFFFAOYSA-N 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 1
- 239000011787 zinc oxide Substances 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
- H03H9/54—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
-
- 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
- H03H9/02007—Details of bulk acoustic wave devices
- H03H9/02086—Means for compensation or elimination of undesirable effects
- H03H9/02102—Means for compensation or elimination of undesirable effects of temperature influence
-
- 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
- H03H9/125—Driving means, e.g. electrodes, coils
- H03H9/13—Driving means, e.g. electrodes, coils for networks consisting of piezoelectric or electrostrictive materials
- H03H9/131—Driving means, e.g. electrodes, coils for networks consisting of piezoelectric or electrostrictive materials consisting of a multilayered structure
-
- 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
Landscapes
- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
Abstract
The application relates to a film bulk acoustic wave filter with a concave-convex temperature compensation layer structure and a preparation method thereof, and belongs to the technical field of film bulk acoustic wave filter processes. The film bulk acoustic wave filter comprises a substrate, wherein a cavity is formed in the center of the substrate, and a lower electrode, a piezoelectric layer, an upper electrode, a protective layer and a bonding pad lead are sequentially prepared on the substrate; the concave-convex temperature compensation layer is arranged above the protective layer, the concave-convex temperature compensation layer is a first convex layer, a first concave layer, a second convex layer, a second concave layer and a third convex layer which are connected from outside to inside, and the thickness of the first convex layer, the second convex layer and the third convex layer is gradually decreased. The concave-convex temperature compensation layer forms a step-shaped structure, so that the thickness of the concave layer can be increased, the process difficulty can be reduced, the film thickness precision can be improved, and the high-frequency performance of the film bulk acoustic wave filter can be further improved. The effect of secondarily suppressing clutter can be achieved, clutter of a passband is further reduced, and the bandwidth is improved.
Description
Technical Field
The patent relates to a film bulk acoustic wave Filter (FBAR) with a concave-convex temperature compensation layer structure and a preparation method thereof, belonging to the technical field of film bulk acoustic wave filter processes.
Background
With mobile communication, there is an urgent need for high-frequency, high-performance, small-volume filters. The film bulk acoustic filter is used for isolating and gating radio frequency signals in the radio frequency front end, limiting radiation signals of a transmitter in an operating frequency band of the film bulk acoustic filter, and preventing interference of received noise signals, and is a key device in a radio frequency system, so that higher requirements are put on passband clutter, bandwidth, loss and frequency temperature coefficient of the film bulk acoustic filter.
The working principle of the micro-sound film bulk acoustic wave filter is as follows: when the electric signal is applied to the transducer, the electric signal is converted into an acoustic signal due to the inverse piezoelectric effect of the piezoelectric film, the acoustic signal propagates in the up-down direction of the transducer respectively, and the acoustic signal is reflected by a reflecting interface formed by air or other structures; the sound wave also has partial transverse propagation while longitudinally propagating, so that the sound wave energy is leaked, and the passband morphology is deteriorated while the loss is increased. The frequency of the micro-sound film bulk acoustic wave filter is determined by the sound velocity and film thickness of the piezoelectric film material, and the higher the sound velocity is, the thinner the film thickness is, and the higher the working frequency of the filter is; the piezoelectric film material is mainly an aluminum nitride piezoelectric film internationally, and the sound velocity of the piezoelectric film material is fixed, so that the higher the frequency is, the thinner the thickness of the film is. The micro-acoustic film bulk acoustic wave filter is composed of series-parallel resonators as shown in fig. 1, and the thickness difference of the thin films of the series-parallel resonators forms impedance characteristics of different frequencies to form the filter.
However, the electrode film material commonly used in the current film bulk acoustic wave filter is Mo, and the higher the frequency is, the thinner the film thickness is, and correspondingly, the thinner the electrode thickening layer of the parallel resonator is, so that the accuracy of the film is difficult to control, the process difficulty is increased, and the performance of the filter cannot meet the requirements.
Based on the above-mentioned problems, the applicant has proposed a film structure of a thin film bulk acoustic wave filter and a method for preparing the same CN111277240a in 2020, which is to manufacture a thickening layer of silicon nitride (or AlN, a material with low mass density) on a protective layer of a parallel resonator, so that the parallel thickening layer of the thin film bulk acoustic wave filter can be increased by 3-4 times compared with the original thickness. However, the applicant found that this structure had the problem of transverse energy leakage, resulting in transverse wave energy loss and even clutter, and also had a large frequency temperature coefficient (-25 to-30 ppm/°c).
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention aims to provide a film bulk acoustic wave filter with a concave-convex temperature compensation layer structure and a preparation method thereof. In order to reduce the process difficulty and improve the precision of the film thickness, the invention adopts the temperature compensation material with smaller mass density as the concave-convex layer structure, can multiply the film thickness of the concave-convex layer structure, better inhibit the transverse clutter, further reduce the loss and the frequency temperature coefficient of the high-frequency filter and improve the performance. Meanwhile, the protective layer of the invention adopts SiO with positive frequency temperature coefficient 2 The film replaces AlN film with negative frequency temperature coefficient; the concave-convex temperature compensation layer film structure is manufactured on the protective layer, and the parallel thickening layer of the film bulk acoustic wave filter can be increased by 3-4 times.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
in a first aspect of the present invention, the present invention provides a thin film bulk acoustic wave filter having a concave-convex temperature compensation layer structure, including a substrate, a cavity is formed in the center of the substrate, and a lower electrode, a piezoelectric layer, an upper electrode, a protective layer and a pad lead are sequentially prepared on the substrate; the protective layer top is provided with unsmooth temperature compensation layer, unsmooth temperature compensation layer is from outside to interior first protruding layer, first sunken layer, second protruding layer, second sunken layer and the protruding layer of third that connects, and the thickness of first protruding layer, the protruding layer of second, the protruding layer of third is progressively decreased in proper order.
Further, the protective layer is made of silicon dioxide.
Furthermore, the concave-convex temperature compensation layer adopts silicon dioxide.
Further, the width of each of the convex layers is 0.5 to 20 μm, and the width of each of the concave layers is 0.1 to 20 μm.
Further, the thickness of the first protruding layer is 30-700 nm, the thickness of the second protruding layer is 30-500 nm, and the thickness of the third protruding layer is 30-300 nm.
Further, the thickness of the first concave layer and the second concave layer is 20-100 nm.
In a second aspect of the present invention, the present invention further provides a method for manufacturing a thin film bulk acoustic wave filter having a concave-convex temperature compensation layer structure, the method comprising:
step 1) preparing a cavity on a substrate;
step 2) preparing a lower electrode by means of direct-current magnetron sputtering coating;
step 3) photoetching and etching the lower electrode to obtain a required lower electrode pattern;
step 4) preparing a piezoelectric layer on the lower electrode pattern by adopting an alternating current magnetron sputtering coating mode by adopting an aluminum nitride material;
step 5) preparing an upper electrode on the piezoelectric layer in a direct-current magnetron sputtering coating mode;
step 6) photoetching and etching the upper electrode to obtain a required upper electrode pattern;
step 7) preparing a protective layer on the upper electrode pattern by a plasma enhanced chemical vapor deposition mode;
step 8) growing a temperature compensation layer in a high-density plasma chemical vapor deposition mode;
step 9) a required concave-convex layer pattern is formed by photoetching and etching, wherein the concave-convex layer pattern is formed by connecting a first convex layer, a first concave layer, a second convex layer, a second concave layer and a third convex layer from outside to inside, and the thicknesses of the first convex layer, the second convex layer and the third convex layer are gradually decreased.
Further, the preparation conditions of the step 8) include a nitrogen flow rate of 1000 to 3000sccm, a silane flow rate of 10 to 30sccm, a nitrous oxide flow rate of 1000 to 3000sccm, and an argon flow rate of 500 to 2000 sccm.
Compared with the prior art, the invention has the following advantages:
(1) The invention adopts SiO with positive frequency temperature coefficient as the protective layer under the condition of not changing the performance of the filter 2 The AlN film with negative frequency temperature coefficient is replaced by the film, so that the frequency temperature coefficient of the filter can be reduced, and the design difficulty is reduced.
(2) The invention prepares the concave-convex layer structure on the protective layer, and the concave-convex layer adopts SiO with positive frequency temperature coefficient and low density 2 The film can increase the thickness of the concave-convex layer and reduce the frequency temperature coefficient. The thickness of the concave layer of the high-density Mo film is only a few nanometers at high frequency, while the invention adopts low-density SiO 2 The thickness of the concave layer of the film can reach tens of nanometers, the process difficulty can be reduced, the film thickness precision is improved, and the high-frequency performance of the film bulk acoustic wave filter is further improved.
(3) The structure adopted by the invention is that the concave-convex layer is manufactured on the protective layer, so that the influence on the performance of the electrode and the film bulk acoustic wave filter can be avoided, the effect of clutter suppression can be achieved, passband ripple can be reduced, bandwidth can be increased, and passband loss can be reduced.
Drawings
Fig. 1 is a schematic circuit diagram of a conventional thin film bulk acoustic filter;
FIG. 2 is a schematic diagram of a conventional thin film bulk acoustic filter;
FIG. 3 is a schematic view of a film bulk acoustic filter with an embossing layer in accordance with an embodiment of the present invention;
FIG. 4 is a graph of performance versus conventional structure and example of the present invention with a relief structure.
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.
The circuit structure of the film bulk acoustic wave filter is shown in figure 1, the film thickness structure is shown in figure 3, and as can be seen from figure 3, the film bulk acoustic wave filter comprises a substrate, a lower electrode, a piezoelectric layer, an upper electrode, a protective layer and a bonding pad lead, wherein a cavity is formed in the center of the substrate; the protective layer top is provided with unsmooth temperature compensation layer, unsmooth temperature compensation layer is from outside to interior first protruding layer, first sunken layer, second protruding layer, second sunken layer and the protruding layer of third that connects, and the thickness of first protruding layer, the protruding layer of second, the protruding layer of third is progressively decreased in proper order.
In an embodiment of the present invention, the substrate may be a substrate stacked with silicon. For example, a silicon wafer is used as the substrate. A cavity is formed in the substrate, and the lower electrode is disposed on the substrate and faces the cavity, i.e., the lower electrode is disposed on the substrate and partially over the cavity.
In an embodiment of the present invention, the lower electrode may be formed of a conductive material such as molybdenum (Mo), ruthenium (Ru), tungsten (W), iridium (Ir), or platinum (Pt) or an alloy of molybdenum (Mo), ruthenium (Ru), tungsten (W), iridium (Ir), or platinum (Pt). In addition, the lower electrode is used as one of an input electrode and an output electrode to which an electric signal such as a Radio Frequency (RF) signal is input. For example, when the lower electrode is an input electrode, the upper electrode is an output electrode, and when the lower electrode is an output electrode, the upper electrode is an input electrode.
In an embodiment of the invention, the piezoelectric layer is formed to at least partially cover the lower electrode. In addition, the piezoelectric layer converts a signal input through the lower electrode or the upper electrode into another signal. The piezoelectric layer may be formed by depositing aluminum nitride, doped aluminum nitride, zinc oxide, or lead zirconate titanate. In addition, in the case where the piezoelectric layer is formed of aluminum nitride (AlN), the piezoelectric layer may further contain a rare earth metal. As an example, the rare earth metal includes at least one of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La). In addition, the aluminum nitride (AlN) piezoelectric layer may also include a transition metal. The transition metal may include at least one of zirconium (Zr), titanium (Ti), manganese (Mn), and hafnium (Hf).
In an embodiment of the present invention, the upper electrode is formed to at least partially cover the piezoelectric layer, and similar to the lower electrode, the upper electrode may still be formed of a conductive material such as molybdenum (Mo), ruthenium (Ru), tungsten (W), iridium (Ir), or platinum (Pt) or an alloy of molybdenum (Mo), ruthenium (Ru), tungsten (W), iridium (Ir), or platinum (Pt). Further, the upper electrode is used as one of an input electrode and an output electrode to which an electric signal such as a Radio Frequency (RF) signal is input. For example, when the upper electrode is an input electrode, the lower electrode is an output electrode, and when the upper electrode is an output electrode, the lower electrode is an input electrode.
In the embodiment of the invention, the protective layer is arranged above the upper electrode, so that the damage to the hierarchical structure below the upper electrode can be prevented, in the conventional film layer structure, the protective layer adopts an AlN film with a negative frequency temperature coefficient, and in the invention, the protective layer adopts SiO with a positive frequency temperature coefficient 2 The AlN film with negative frequency temperature coefficient is replaced by the film, so that the frequency temperature coefficient of the filter can be reduced, and the design difficulty is reduced. In addition, the growth of the protective layer on the upper electrode does not affect the orientation and the effective electromechanical coupling coefficient of the piezoelectric layer, and the influence on the performance of the thin film bulk acoustic wave filter can be reduced.
In the embodiment of the invention, the concave-convex temperature compensation layer is formed to at least partially cover the protective layer, and the concave-convex layer structure is prepared on the protective layer and consists of a first convex layer, a first concave layer, a second convex layer, a second concave layer and a third convex layer which are connected from outside to inside. The effect of secondarily suppressing clutter can be achieved, clutter of a passband is further reduced, and the bandwidth is improved.
In the conventional structure, a high-density Mo film is generally used as a thickening layer, and the concave-convex layer of the invention adopts SiO with positive frequency temperature coefficient and low density 2 The film can increase the thickness of the concave-convex layer and reduce the frequency temperature coefficient. The thickness of the concave layer of the high-density Mo film is only a few nanometers at high frequency, while the concave layer of the low-density SiO film is adopted 2 The thickness of the concave layer of the film can reach tens of nanometers, the process difficulty can be reduced, the precision of the film thickness can be improved, and the high-frequency performance of the filter can be further improved.
The concave-convex layer structure for inhibiting the transverse clutter is thinner, so that the process difficulty is increased; however, the film thickness is too thin, the accuracy is difficult to control, and the film thickness of the concave-convex layer structure (especially the concave layer) is inaccurate, so that not only clutter cannot be inhibited, but also the performance of the filter is deteriorated.
By way of example, the width d1 of each raised layer is 0.5 to 20 μm and the width d2 of each recessed layer is 0.1 to 20 μm.
As an example, the thickness of the first bump layer is 30 to 700nm, the thickness of the second bump layer is 30 to 500nm, and the thickness of the third bump layer is 30 to 300nm. By the arrangement of the thickness and the width, transverse sound waves can be restrained, transverse wave energy is restrained, and transverse wave energy loss and clutter generation are reduced.
In the embodiment of the invention, the thickness of the first concave layer and the second concave layer is 20-100 nm. The thickness of the concave layer can reach tens of nanometers, the process difficulty can be reduced, the precision of the film thickness can be improved, and the high-frequency performance of the film bulk acoustic wave filter can be further improved.
In some preferred embodiments, a sacrificial layer may be provided on the substrate, the sacrificial layer preventing damage to the substrate when the cavity is formed. As an example, the sacrificial layer is made of a material containing silicon nitride or silicon dioxide (SiO 2 ) Is formed of the material of (a). The sacrificial layer may be removed by a halide-based etching gas. The sacrificial layer surrounding the cavity portion is more easily etched further than the cavity portion of the sacrificial layer corresponding to the central portion of the filter.
The conventional structure and the relief structure filter performance pair are shown in fig. 4, for example. The 1dB bandwidth of the conventional structure filter is 5.6MHz, the top loss is 1.4dB, and the frequency temperature coefficient is-25 to-30 ppm/DEG C; the 1dB bandwidth of the concave-convex structure filter is 26.4MHz, the top loss is 1.1dB, and the frequency temperature coefficient is-2 to-15 ppm/DEG C. SiO is adopted 2 After the film is used as a protective layer and a concave-convex layer structure, the bandwidth of the filter is increased by 4.7 times, and the loss and the frequency temperature coefficient can be greatly reduced.
In the common semiconductor material, mo has a density of 10280kg/m 3 The sound velocity is 6214m/s; siO (SiO) 2 Has a density of 2000kg/m 3 The sound velocity is 6253m/s, under the condition of the same frequency, siO 2 The thickness is 3-4 times of the thickness of Mo. The frequency temperature coefficient of the Mo-AlN-Mo-AlN structure is-25 to-30 ppm/DEG C, siO 2 The temperature coefficient of the frequency is +85 ppm/DEG C, the invention uses SiO on the protective layer 2 The frequency temperature coefficient of the filter can be greatly reduced after AlN is replaced.
Based on the new film structure, the invention provides a new film structure of a film bulk acoustic wave filter and a process method thereof, wherein the process steps are as follows:
step 1) preparing a cavity on a substrate;
step 2) preparing a lower electrode by means of direct-current magnetron sputtering coating;
step 3) photoetching and etching the lower electrode to obtain a required lower electrode pattern;
step 4) preparing a piezoelectric layer on the lower electrode pattern by adopting an alternating current magnetron sputtering coating mode by adopting an aluminum nitride material;
step 5) preparing an upper electrode on the piezoelectric layer in a direct-current magnetron sputtering coating mode;
step 6) photoetching and etching the upper electrode to obtain a required upper electrode pattern;
step 7) preparing a protective layer on the upper electrode pattern by a plasma enhanced chemical vapor deposition mode;
step 8) growing a temperature compensation layer in a high-density plasma chemical vapor deposition mode;
step 9) a required concave-convex layer pattern is formed by photoetching and etching, wherein the concave-convex layer pattern is formed by connecting a first convex layer, a first concave layer, a second convex layer, a second concave layer and a third convex layer from outside to inside, and the thicknesses of the first convex layer, the second convex layer and the third convex layer are gradually decreased.
In a preferred embodiment of the present invention, the present invention may further comprise the steps of:
(1) A cavity is prepared on the silicon wafer, and the lower electrode is prepared by a direct current magnetron sputtering coating mode at 100-350 nm. And then the needed lower electrode pattern manufacturing process is obtained through photoetching and etching:
(2) After the needed lower electrode pattern is obtained, preparing a piezoelectric layer film AlN 300-2000 nm on the lower electrode pattern by an alternating current magnetron sputtering coating mode, wherein the prepared piezoelectric film has better c-axis orientation and smaller stress.
(3) And preparing an upper electrode of 100-600 nm on the piezoelectric layer film by means of direct-current magnetron sputtering coating, and obtaining a required upper electrode pattern by photoetching and etching.
(4) Growth of SiO by means of Plasma Enhanced Chemical Vapor Deposition (PECVD) 2 And the protective layer is 30-700 nm, and the required concave-convex layer pattern is formed through photoetching and etching.
(5) Wherein d1 has a size of 0.5 to 20 μm and d2 has a size of 0.1 to 20. Mu.m.
The film structure process adopts a silicon wafer as a substrate material, firstly, a cavity is dug out on the substrate, then a lower electrode, a piezoelectric layer, an upper electrode, a protective layer and a concave-convex layer are sequentially arranged on the substrate and the cavity, finally, a bonding pad lead electrode is prepared, and the performance of the film bulk acoustic wave filter is obtained through the bonding pad lead electrode.
The invention adopts SiO 2 As a protective layer and a concave-convex layer, the frequency temperature characteristic of the filter is improved, the process difficulty of preparing the film of the film bulk acoustic wave filter can be greatly reduced, the thickness of the concave-convex layer is increased, and the thickness of the thinnest concave layer is increased from a few nanometers to tens of nanometers. The thickness of the concave layer film is increased, the design difficulty of the filter is reduced, and meanwhile, the manufacturability of the film is improved; after the thickness of the concave layer is increased, the precision of the film is easier to control, the clutter suppression effect is better, the passband ripple of the filter is smaller, and the bandwidth is increased. The increase of the passband bandwidth improves the rectangle degree of the filter, reduces the interference signal entering the receiver, and improves the signal-to-noise ratio and the equipment sensitivity of the whole machine; meanwhile, the filter can keep the performance unchanged when working in a severe environment.
The above examples of the present invention are merely illustrative of the present invention and are not intended to limit the embodiments of the present invention. Other variations and modifications of the present invention will be apparent to those of ordinary skill in the art in light of the foregoing description. Not all embodiments are exhaustive. Obvious changes and modifications which are extended by the technical proposal of the invention are still within the protection scope of the invention.
In the description of the present invention, it should be understood that the terms "coaxial," "bottom," "one end," "top," "middle," "another end," "upper," "one side," "top," "inner," "outer," "front," "center," "two ends," etc. indicate or are based on the orientation or positional relationship shown in the drawings, merely to facilitate description of the invention and simplify 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 therefore should not be construed as limiting the invention.
In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "configured," "connected," "secured," "rotated," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly through intermediaries, or in communication with each other or in interaction with each other, unless explicitly defined otherwise, the meaning of the terms described above in this application will be understood by those of ordinary skill in the art in view of the specific circumstances.
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 (8)
1. The film bulk acoustic wave filter with the concave-convex temperature compensation layer structure comprises a substrate, wherein a cavity is formed in the center of the substrate, and a lower electrode, a piezoelectric layer, an upper electrode, a protective layer and a bonding pad lead are sequentially prepared on the substrate; the protective layer is characterized in that a concave-convex temperature compensation layer is arranged above the protective layer, the concave-convex temperature compensation layer is a first convex layer, a first concave layer, a second convex layer, a second concave layer and a third convex layer which are connected from outside to inside, and the thicknesses of the first convex layer, the second convex layer and the third convex layer decrease in sequence.
2. The thin film bulk acoustic filter having a concave-convex temperature compensating layer structure as claimed in claim 1, wherein said protective layer is silicon dioxide.
3. The thin film bulk acoustic filter having a structure of a concave-convex temperature compensating layer according to claim 1, wherein the concave-convex temperature compensating layer is made of silicon dioxide.
4. The thin film bulk acoustic filter having a concave-convex temperature compensating layer structure as claimed in claim 1, wherein the width of each of the convex layers is 0.5 to 20 μm and the width of each of the concave layers is 0.1 to 20 μm.
5. The thin film bulk acoustic filter having a concave-convex temperature compensating layer structure as claimed in claim 1, wherein the thickness of the first convex layer is 30 to 700nm, the thickness of the second convex layer is 30 to 500nm, and the thickness of the third convex layer is 30 to 300nm.
6. The thin film bulk acoustic filter having a concave-convex temperature compensating layer structure as claimed in claim 1, wherein the thickness of the first concave layer and the second concave layer is 20 to 100nm.
7. The preparation method of the film bulk acoustic wave filter with the concave-convex temperature compensation layer structure is characterized by comprising the following steps of:
step 1) preparing a cavity on a substrate;
step 2) preparing a lower electrode by means of direct-current magnetron sputtering coating;
step 3) photoetching and etching the lower electrode to obtain a required lower electrode pattern;
step 4) preparing a piezoelectric layer on the lower electrode pattern by adopting an alternating current magnetron sputtering coating mode by adopting an aluminum nitride material;
step 5) preparing an upper electrode on the piezoelectric layer in a direct-current magnetron sputtering coating mode;
step 6) photoetching and etching the upper electrode to obtain a required upper electrode pattern;
step 7) preparing a protective layer on the upper electrode pattern by a plasma enhanced chemical vapor deposition mode;
step 8) growing a temperature compensation layer in a high-density plasma chemical vapor deposition mode;
step 9) patterning and etching to the desired levelThe concave-convex layer pattern is a first convex layer and a first concave layer which are connected from outside to inside 、 The thicknesses of the first convex layer, the second convex layer and the third convex layer decrease in sequence.
8. The method of manufacturing a thin film bulk acoustic filter having a concave-convex temperature compensating layer structure according to claim 7, wherein the manufacturing conditions in the step 8) include a nitrogen flow of 1000 to 3000sccm, a silane flow of 10 to 30sccm, a nitrous oxide flow of 1000 to 3000sccm, and an argon flow of 500 to 2000 sccm.
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