CN114337572A - Bulk acoustic wave resonator, doping concentration determination method, filter, and electronic device - Google Patents
Bulk acoustic wave resonator, doping concentration determination method, filter, and electronic device Download PDFInfo
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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
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H9/00—Networks comprising electromechanical or electro-acoustic devices; Electromechanical resonators
- H03H9/15—Constructional features of resonators consisting of piezoelectric or electrostrictive material
- H03H9/17—Constructional features of resonators consisting of piezoelectric or electrostrictive material having a single resonator
-
- 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
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- Physics & Mathematics (AREA)
- Acoustics & Sound (AREA)
- Piezo-Electric Or Mechanical Vibrators, Or Delay Or Filter Circuits (AREA)
Abstract
The invention relates to a bulk acoustic wave resonator comprising: a substrate; an acoustic mirror; a bottom electrode; a piezoelectric layer comprising a doping element having a corresponding doping concentration; and a top electrode, wherein: the resonance frequency of the resonator is higher than 2.5GHz, and the resonator has a layer thickness ratio E/P; the resonator has an electromechanical coupling coefficient Kt2The doping concentration is less than a1, and the electromechanical coupling coefficient Kt is the layer thickness ratio E/P of 3 when a1 is2Corresponding doping concentration. The invention also relates to a method for determining the doping concentration of the doping element of the piezoelectric layer of a bulk acoustic wave resonator having an electromechanical coupling coefficient Kt2The resonator has a resonance frequency higher than 2.5GHz and has a layer thickness ratio E/P, the method comprising the steps ofThe method comprises the following steps: selecting the doping concentration to be less than a1 based on the layer thickness ratio E/P, wherein a1 is the electromechanical coupling coefficient Kt when the layer thickness ratio E/P of the resonator is 32Corresponding doping concentration. The invention also relates to a filter and an electronic device.
Description
Technical Field
Embodiments of the present invention relate to the field of semiconductors, and in particular, to a bulk acoustic wave resonator, a method for determining doping concentration, a filter, and an electronic device.
Background
With the development of 5G communication technology, the communication technology puts higher and higher requirements on the large bandwidth of the filter. Under the premise, the design pair of the filter has a larger effective electromechanical coupling coefficient (kt)2) The resonator of (a) poses an urgent need.
As a novel MEMS device, the Film Bulk Acoustic Resonator (FBAR) has the advantages of small volume, light weight, low insertion loss, wide frequency band, high quality factor and the like, and is well suitable for the update of a wireless communication system.
In the prior art, there is still kt at which the resonator is maintained2The larger the requirements for an increased Q-value of the resonator.
Furthermore, as the frequency of the resonator increases, at Kt2If the resonator area is fixed, the resonator area is reduced, which is advantageous for downsizing the resonator and the filter, but if the resonator area is too small, the power capacity per unit area of the resonator is problematic if the power of the resonator is large. When the power that a single resonator should withstand is constant, the smaller the area the higher the power density and therefore the easier the resonator burns out.
Thus, there are also prior art resonators that maintain a high frequency kt2Larger so that its area is not too small.
Disclosure of Invention
The present invention has been made to mitigate or solve at least one of the above-mentioned problems in the prior art.
According to an aspect of an embodiment of the present invention, there is provided a bulk acoustic wave resonator including:
a substrate;
an acoustic mirror;
a bottom electrode;
a piezoelectric layer comprising a doping element having a corresponding doping concentration; and
a top electrode is arranged on the top of the substrate,
wherein:
the resonance frequency of the resonator is higher than 2.5GHz, and the resonator has a layer thickness ratio E/P;
the resonator has an electromechanical coupling coefficient Kt2The doping concentration is less than a1, and the electromechanical coupling coefficient Kt is the layer thickness ratio E/P of 3 when a1 is2Corresponding doping concentration.
Embodiments of the present invention also relate to a method of determining a doping concentration of a doping element of a piezoelectric layer of a bulk acoustic wave resonator having an electromechanical coupling coefficient Kt2The resonator has a resonant frequency higher than 2.5GHz and has a layer thickness ratio E/P, the method comprising the steps of:
selecting the doping concentration to be less than a1 based on the layer thickness ratio E/P, wherein a1 is the electromechanical coupling coefficient Kt when the layer thickness ratio E/P of the resonator is 32Corresponding doping concentration.
Embodiments of the invention also relate to a filter comprising a resonator as described above.
Embodiments of the invention also relate to an electronic device comprising a filter as described above or a resonator as described above.
Drawings
These and other features and advantages of the various embodiments of the disclosed invention will be better understood from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate like parts throughout, and in which:
FIG. 1 is a schematic cross-sectional view of a bulk acoustic wave resonator;
FIG. 2 is a graph exemplarily showing the relationship between the E/P value and the width of the bump structure and the Q value of the resonator;
FIG. 3 is a graph schematically illustrating the relationship between the width of the bump structure and the Q value of the resonator;
FIG. 4 is a graph illustrating an E/P value and Kt2A relationship diagram of (1);
FIG. 5 illustrates the case where E/P-3 is dopedImpurity concentration and Kt2A relationship diagram of (1);
FIG. 6 illustrates the doping concentration and Kt for the case of E/P2.82A relationship diagram of (1);
FIG. 7 illustrates the doping concentration vs. Kt for the case of E/P2.62A relationship diagram of (1);
FIG. 8 illustrates the doping concentration vs. Kt for the case of E/P2.42A relationship diagram of (1);
FIG. 9 illustrates the doping concentration and Kt for the case of E/P2.22A relationship diagram of (1);
FIG. 10 illustrates the doping concentration vs. Kt for the case of E/P22A relationship diagram of (1);
FIG. 11 shows exemplary doping concentrations and Kt for E/P1.82A relationship diagram of (1);
FIG. 12 shows exemplary doping concentrations and Kt for E/P of 1.02A relationship diagram of (1);
FIG. 13 illustrates the doping concentration and Kt for the case where E/P is 0.852A relationship diagram of (1);
FIG. 14 shows exemplary doping concentrations and Kt for E/P of 0.752A relationship diagram of (1);
FIG. 15 is a diagram exemplarily showing at Kt2E/P value in the case of 5.9% as a function of the area of the resonator;
FIG. 16 illustrates a resonator with a frequency of 3.5GHz at Kt2Doping concentration versus resonator area for 5.9%; and
FIG. 17 illustrates a resonator with a frequency of 1.75GHz, at Kt2Doping concentration versus resonator area in the case of 5.9%.
Detailed Description
The technical scheme of the invention is further specifically described by the following embodiments and the accompanying drawings. In the specification, the same or similar reference numerals denote the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the general inventive concept of the present invention and should not be construed as limiting the invention. Some, but not all embodiments of the invention are described. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.
Fig. 1 shows a cross-sectional view of a typical sandwich structure bulk acoustic wave resonator. In fig. 1, reference numerals are illustrated as follows:
101: the substrate can be selected from monocrystalline silicon, gallium nitride, gallium arsenide, sapphire, quartz, silicon carbide, diamond and the like.
102: the acoustic mirror can be a cavity, and a Bragg reflection layer and other equivalent forms can also be adopted. The embodiment of the present invention takes the form of a cavity.
103: the bottom electrode (including the bottom electrode pin) can be made of molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the metals or an alloy thereof.
104: the piezoelectric layer can be a single crystal piezoelectric material, and can be selected from the following: the material may be polycrystalline piezoelectric material (corresponding to single crystal, non-single crystal material), optionally, polycrystalline aluminum nitride, zinc oxide, PZT, or a rare earth element doped material containing at least one rare earth element, such as scandium (Sc), yttrium (Y), magnesium (Mg), titanium (Ti), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), erbium (Ho), erbium (holmium), thulium (Tm), ytterbium (Yb), lutetium (Lu), or the like.
105: the top electrode (including the top electrode pin) can be made of molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the metals or an alloy thereof.
106: a passivation layer or process layer, which may be aluminum nitride, silicon dioxide, or the like.
107: the material of the convex structure can be selected from molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or the composition of the above metals or the alloy thereof, and the like.
For bulk acoustic wave resonators, the electromechanical coupling coefficient Kt2Is related to the value of the layer thickness ratio E/P and the doping concentration of the doping element in the piezoelectric layer. Further, the Q value of the bulk acoustic wave resonator is correlated with the value of the layer thickness ratio E/P.
Further, the area of the resonator (which refers to the area of the effective area of the resonator, and the effective area refers to the area formed by the overlapping portions of the top electrode, the piezoelectric layer, the bottom electrode, and the acoustic mirror of the resonator in the thickness direction of the resonator) decreases as the resonance frequency of the resonator increases with a fixed electromechanical coupling coefficient of the resonator.
The present invention proposes a method for maintaining Kt by selecting a doping concentration lower than a doping concentration based on a specific layer thickness ratio (i.e., setting an upper limit value of the doping concentration)2Stabilization and the ability to alleviate or eliminate the power capability problem caused by the small area per unit area of the resonator in cases where the area of the resonator is relatively small.
The invention can also further limit the lower limit value of the layer-thickness ratio, and the performance of the resonator is improved based on the layer-thickness ratio higher than the lower limit value of the layer-thickness ratio.
The layer thickness ratio E/P will be briefly described below.
As shown in fig. 1, the thickness of the bottom electrode 103 is t1, the thickness of the piezoelectric layer 104 is t2, the thickness of the top electrode 105 is t3, and the thickness of the passivation layer 106 above the top electrode is t 4. When the passivation layer 106 is not provided, the ratio of the electrode thickness to the piezoelectric layer thickness, i.e., the layer thickness ratio E/P, is defined as (t1+ t3)/t 2. When the resonator has the passivation layer 106, the electrode thickness to piezoelectric layer thickness ratio is defined, that is, the layer thickness ratio E/P is (t1+ t3+ t4 a)/t2, where a has a relationship with the ratio of the influence rate of the passivation layer 106 on the resonance frequency Fs and the influence rate of the top electrode 105 on the resonance frequency Fs, and specifically, assuming that the influence rate of the thickness of the passivation layer 106 on the resonance frequency Fs is V1 nm/MHz and the influence rate of the thickness of the top electrode 105 on the resonance frequency Fs is V2 nm/MHz, a is V2/V1. If the top and bottom electrode materials are Mo and the passivation layer is AlN, the value of a is approximately 1/3. The layer thickness ratio E/P can also be calculated based on the above concept if the stacked structure of the resonator is added with other functional layers on the basis of the above.
The doping concentration of the element doped in the piezoelectric layer is briefly described below.
Doped means that a portion of one or more elements in the piezoelectric material that was not doped originally is replaced with a doping element. The doping concentration is defined here as: the number of atoms of the doping element per unit volume is the ratio of the total number of atoms of the one or more elements partially replaced by the doping element mentioned above to the sum of the number of atoms of the doping element. For example, in the case where the piezoelectric layer is aluminum nitride and the doping element is scandium, part of the aluminum atoms are replaced with scandium atoms, and the doping concentration is the ratio of the number of scandium atoms per unit volume to the sum of the number of aluminum atoms and the number of scandium atoms (Sc/Al + Sc).
Fig. 2 is a graph exemplarily showing a relationship between a layer thickness ratio E/P value and a bump structure width and a Q value of a resonator. In fig. 2, the ordinate is the Q value of the resonator, and the abscissa has two layers, the first layer being the layer thickness ratio E/P of the resonator and the second layer being the width L (in μm) of the bump structure 107. Based on the first layer, FIG. 2 shows the variation of the Q value of the resonator in the Band1TX Band (1920-. Based on the second layer, fig. 2 shows exemplary Q values of the resonator at different bump structure widths L for different layer thickness ratios E/P.
Fig. 3 exemplarily shows a graph of a relationship between the width L of the bump structure and the Q value of the resonator in the case where the layer thickness ratio E/P is 1. As can be seen from fig. 3, the Q value of the resonator varies with the bump width L, and there are two peaks when the bump width L is about 1.25um and L is about 5.25 um. However, referring to fig. 2, when the layer thickness ratio E/P is less than 1, the peaks of the corresponding two Q values in fig. 3 deteriorate as the layer thickness ratio E/P becomes smaller. Referring to fig. 2, when E/P is 0.65, both maximum values of the Q value in fig. 3 deteriorate by more than 20%, and the maximum value when L is 1.25 is not present.
Therefore, the value of the layer thickness ratio E/P can directly influence the Q value of the resonator. In order to obtain a good resonator Q value, the layer thickness ratio E/P should be not less than 0.75.
FIG. 4 is a graph illustrating an E/P value and Kt2In which the abscissa is the E/P value and the ordinate is Kt2. More specifically, fig. 4 exemplarily shows kt at a doping concentration of 8.2% when the piezoelectric layer is an aluminum nitride-doped piezoelectric layer of scandium metal2As a function of the layer thickness ratio E/P. It can be seen that kt decreases as the layer thickness ratio E/P decreases2And (4) rising. However, the conclusion from FIG. 2 is that kt cannot be boosted by infinitely lowering the E/P value without seriously degrading the resonator performance2。
FIGS. 5-14 illustrate doping concentration versus Kt2In which the abscissa is the doping concentration and the ordinate is Kt2. It can be seen that as the doping concentration increases, Kt2And (4) improving.
Thus, a higher value of the layer thickness ratio E/P can be selected, for example, the value of the layer thickness ratio E/P should not be lower than 0.75, to ensure a higher Q value of the resonator (but now Kt2Does not meet or does not completely meet performance requirements) while increasing Kt by selecting a doping concentration above a predetermined value2To meet performance requirements or to improve performance. Therefore, kt can be increased by increasing the doping concentration on the premise of ensuring the performance (higher Q value) of the resonator2。
Due to Kt2The value of E/P is limited to the lower limit (not less than 0.75 as described above) depending on the value of E/P and the doping concentration, so that Kt is desirable even when Kt is used2The larger the better, the better Kt2There is also an upper limit value, which is determined by the lower limit value of E/P, 0.75.
In other words, in the present invention, for the bulk acoustic wave filter, the kt of the resonator can be raised by selecting the doping concentration2. However for the selection of kt2The doping concentration of the resonator has a better range determined by the E/P value so as to ensure the high performance of the resonator.
Further, the area a of the resonator satisfies the following formula:
A∝t2/(Fs*ε)–(1)
area of A:50 omega resonator
t 2: thickness of piezoelectric layer
Fs: resonant frequency of resonator
Epsilon: dielectric constant of piezoelectric layer
At a fixed kt as the frequency increases2The thickness t2 of the piezoelectric layer becomes smaller. As can be understood from the above formula (1), as the frequency Fs increases, the area of the 50 Ω resonator becomes smaller. For example, when kt is 02At 5.9%, the 50 Ω resonator area at 1.75GHz is about 21000 μm, see FIG. 172And, referring to fig. 16, the 50 Ω resonator area at 3.5GHz is about 5200 μm2. When the frequency of the resonator is raised and thus the area becomes small, as mentioned in the background art, in the case where the power of the resonator is large, a problem of power capacity per unit area of the resonator occurs. When the power that a single resonator should withstand is constant, the smaller the area the higher the power density and therefore the easier the resonator burns out. Therefore, for high frequency filters or resonators, e.g. with frequencies above 2.5GHz, it is desirable to consider increasing the area of the resonator to reduce or eliminate the risk of the resonator burning out due to an excessive power capacity per unit area.
FIG. 15 is a graph illustrating the E/P value of the layer thickness ratio versus the area of the resonator, where Kt2The content was found to be 5.9%. In FIG. 15, the vertical axis represents the area of the resonator in μm2The horizontal axis represents the E/P value. Thus, for a fixed Kt2Based on the illustration in fig. 15, the area of the resonator can be increased by decreasing the layer thickness ratio E/P. As shown in FIG. 4, as the E/P value decreases, Kt is constant at a constant doping concentration2Will rise. Furthermore, referring to FIGS. 5-14, for a fixed E/P value, Kt decreases as the doping concentration decreases2It will decrease. Based on the above, Kt is maintained in order to increase the area of the high-frequency resonator2Stable, the layer thickness ratio E/P can be reduced to increase the area, and the doping concentration is reduced to maintain the Kt of the resonator2Stable (i.e. unchanged or 5% floating from the original value, in the examples of the present invention, the description is made by way of example of the retention of invariance).
Thus, if necessary, byChoosing to reduce the value of the layer-thickness ratio E/P to increase the area of the resonator (a smaller value of the layer-thickness ratio E/P will result in the Kt of the resonator2Increased), it may be desirable to simultaneously use a reduced dopant concentration to reduce Kt2To maintain Kt2And (4) stabilizing. Since the larger the area of the resonator is expected to be, the smaller the E/P value is, the lower the E/P value and the doping concentration corresponding to the E/P value can be selected, thereby ensuring that the area of the resonator is not too small to cause the problem of power capacity and the Kt of the resonator2And (4) stabilizing.
In the present invention, the value of the layer thickness ratio E/P is selected to be not more than 3 and the upper limit value of the doping concentration is determined based on the E/P value. Specifically, in the present invention, for the bulk acoustic wave filter, the area of the resonator can be increased by selectively lowering the E/P value, but in order to maintain kt of the resonator2Stable, or for a selected kt2The resonator of (1) further needs to set the doping concentration in a preferable range whose upper limit is determined based on a smaller value of the layer thickness ratio E/P (3 in the present invention), so that the area of the resonator can be increased (by selecting a smaller value of E/P), and Kt can be maintained by selecting a smaller doping concentration value corresponding to the value of E/P2And (4) stabilizing. That is, in the present invention, for a high frequency resonator, for example, a resonator with a frequency higher than 2.5GHz, if both the performance of the resonator and the area of the resonator are to be ensured, not only the doping concentration needs to meet the performance requirement, but also an upper limit based on the area requirement of the resonator is required. For high-frequency products, the E/P value is less than 3, and the doping concentration is less than the doping concentration corresponding to E/P-3, so that the area of the resonator is increased, and the related performance requirements of the resonator are met.
Based on the above, the invention provides a bulk acoustic wave resonator, wherein the piezoelectric layer of the bulk acoustic wave resonator is a piezoelectric layer including doping elements, the doping elements have corresponding doping concentrations, the resonance frequency of the resonator is higher than 2.5GHz, and the resonator has a layer thickness ratio E/P; the resonator has an electromechanical coupling coefficient Kt2The doping concentration is less than a1, and the electromechanical coupling coefficient Kt is the layer thickness ratio E/P of 3 when a1 is2Corresponding doping concentration.
Based on the above, the invention also provides a method for determining doping concentration of a piezoelectric layer of a bulk acoustic wave resonator, wherein the piezoelectric layer of the resonator is a piezoelectric layer comprising doping elements, the doping elements have corresponding doping concentrations, the resonant frequency of the resonator is higher than 2.5GHz, and the resonator has a layer thickness ratio E/P; the resonator has an electromechanical coupling coefficient Kt2The method comprises the following steps: selecting the doping concentration to be less than a1 based on the layer thickness ratio E/P, wherein a1 is the electromechanical coupling coefficient Kt when the layer thickness ratio E/P of the resonator is 32Corresponding doping concentration.
In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped metal scandium-doped piezoelectric layer, the electromechanical coupling coefficient Kt is set when the upper limit value a1 of the doping concentration is 3 of the layer thickness ratio E/P2The corresponding doping concentration, and is determined by the following formula: kt2＝0.2977a12+0.2085a1+ 0.033. In fig. 5, the doping concentrations a1 and Kt are shown for the case of E/P ═ 32In FIG. 5, y corresponds to Kt2And x corresponds to the doping concentration a 1.
In one embodiment of the invention, the resonant frequency of the resonator is higher than 3.0GHz, the doping concentration is less than a2, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient Kt when the thickness ratio E/P of the resonator layer is 2.8 in a22Corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped metal scandium-doped piezoelectric layer, the electromechanical coupling coefficient Kt is set such that the upper limit value a2 of the doping concentration is 2.8 of the layer thickness ratio E/P2The corresponding doping concentration, and is determined by the following formula: kt2＝0.3093a22+0.2149a2+ 0.0342. In fig. 6, the doping concentrations a2 and Kt are shown for the case of E/P2.82In FIG. 6, y corresponds to Kt2And x corresponds to the doping concentration a 2.
In one embodiment of the invention, the resonance frequency of the resonator is higher than 3.5 GHz; the doping concentration is less than a3, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a3 is the thickness ratio E/P of the resonator layer is 2.62Corresponding doping concentration. In more specific embodiments of the inventionWhen the piezoelectric layer is an aluminum nitride-doped metal scandium-doped piezoelectric layer, the electromechanical coupling coefficient Kt is determined when the upper limit value a3 of the doping concentration is 2.6 of the layer thickness ratio E/P2The corresponding doping concentration, and is determined by the following formula: kt2＝0.3437a32+0.2137a3+ 0.0364. In fig. 7, the doping concentrations a3 and Kt are shown for the case of E/P2.62In FIG. 7, y corresponds to Kt2And x corresponds to the doping concentration a 3.
In one embodiment of the invention, the resonance frequency of the resonator is higher than 4 GHz; the doping concentration is less than a4, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a4 is the thickness ratio E/P of the resonator layer is 2.42Corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped metal scandium-doped piezoelectric layer, the electromechanical coupling coefficient Kt is set such that the upper limit value a4 of the doping concentration is 2.4 of the layer thickness ratio E/P2The corresponding doping concentration, and is determined by the following formula: kt2＝0.3508a42+0.2213a4+ 0.0378. In fig. 8, the doping concentrations a4 and Kt are shown for the case of E/P2.42In FIG. 8, y corresponds to Kt2And x corresponds to the doping concentration a 4.
In one embodiment of the invention, the resonance frequency of the resonator is higher than 4.5 GHz; the doping concentration is less than a5, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a5 is the thickness ratio E/P of the resonator layer is 2.22Corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped metallic scandium-based piezoelectric layer, the electromechanical coupling coefficient Kt is set such that the upper limit value a5 of the doping concentration is 2.2 as the layer thickness ratio E/P2The corresponding doping concentration, and is determined by the following formula: kt2＝0.3345a52+0.2352a5+ 0.0399. In fig. 9, the doping concentrations a5 and Kt are shown for the case of E/P2.22In FIG. 9, y corresponds to Kt2And x corresponds to the doping concentration a 5.
In one embodiment of the invention, the resonance frequency of the resonator is higher than 5 GHz; the doping concentration is less than a6, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a6 is the thickness ratio E/P of the resonator layer is 22Corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped metal scandium-doped piezoelectric layer, the electromechanical coupling coefficient Kt is set when the upper limit value a5 of the doping concentration is 2 of the layer thickness ratio E/P2The corresponding doping concentration, and is determined by the following formula: kt2＝0.407a62+0.2315a6+ 0.0421. In fig. 10, the doping concentrations a6 and Kt are shown for the case of E/P22In FIG. 10, y corresponds to Kt2And x corresponds to the doping concentration a 6.
In one embodiment of the invention, the resonance frequency of the resonator is higher than 6 GHz; the doping concentration is less than a7, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a7 is the thickness ratio E/P of the resonator layer is 1.82Corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped metallic scandium-based piezoelectric layer, the electromechanical coupling coefficient Kt is set such that the upper limit value a7 of the doping concentration is 1.8 when the layer thickness ratio E/P is2The corresponding doping concentration, and is determined by the following formula: kt2＝0.4801a72+0.2157a7+ 0.0461. In fig. 11, the doping concentrations a6 and Kt are shown for the case where E/P is 1.82In FIG. 11, y corresponds to Kt2And x corresponds to the doping concentration a 7.
Further, as already mentioned above, for the E/P value, in order to make the Q value of the resonator at a relatively high value, the E/P value is not less than 0.75.
In one embodiment of the invention, the doping concentration is not less than b1, and b1 is the electromechanical coupling coefficient Kt when the thickness ratio E/P of the resonator layer is 0.752Corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped metallic scandium-based piezoelectric layer, the electromechanical coupling coefficient Kt when the lower limit value b1 of the doping concentration is 0.75 of the layer thickness ratio E/P2The corresponding doping concentration, and is determined by the following formula: kt2＝0.3909b12+0.3056b1+ 0.062. In fig. 14, the doping concentrations b1 and Kt are shown for the case where E/P is 0.752In FIG. 14, y corresponds to Kt2And x corresponds to the doping concentration b 1.
In one embodiment of the invention, the doping concentration is not less than b2, and b2 is the electromechanical coupling coefficient Kt when the thickness ratio E/P of the resonator layer is 0.852Corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped metallic scandium-based piezoelectric layer, the electromechanical coupling coefficient Kt is set when the lower limit value b2 of the doping concentration is 0.85 of the layer thickness ratio E/P2The corresponding doping concentration, and is determined by the following formula: kt2＝0.4463b22+0.2869b2+ 0.0603. In fig. 13, the doping concentrations b2 and Kt are shown for the case where E/P is 0.852In FIG. 13, y corresponds to Kt2And x corresponds to the doping concentration b 2.
In one embodiment of the invention, the doping concentration is not less than b3, b3 is the electromechanical coupling coefficient Kt when the thickness ratio E/P of the resonator layer is 12Corresponding doping concentration. In a more specific embodiment of the present invention, when the piezoelectric layer is an aluminum nitride-doped metal scandium-doped piezoelectric layer, the electromechanical coupling coefficient Kt is set such that the lower limit value b3 of the doping concentration is 1 when the layer thickness ratio E/P is2The corresponding doping concentration, and is determined by the following formula: kt2＝0.4147b32+0.2774b3+ 0.057. In fig. 12, the doping concentrations b3 and Kt are shown for the case where E/P is 12In FIG. 12, y corresponds to Kt2And x corresponds to the doping concentration b 3.
The above resonators (choosing appropriate doping concentration based on layer thickness ratio E/P to increase resonator area while maintaining Kt2Stable) may also be used for the filter.
In one embodiment of the invention, the filter is a filter in 2.515GHz-2.675GHz band or 3.3GHz-3.6GHz band; and the doping concentration of the resonators in the filter ranges from 14.4% to 26.5%. Further, the doping concentration of the resonator in the filter ranges from 15.7% to 26.5%.
In one embodiment of the invention, the filter is a filter in a 4.8GHz-4.96GHz band; and the doping concentration of the resonators in the filter ranges from 1% to 12.4%. Further, the doping concentration of the resonator in the filter ranges from 2.6% to 12.4%.
In one embodiment of the invention, the filter is a filter in a frequency band of 5.15GHz-5.85 GHz; and the doping concentration of the resonators in the filter ranges from 28.5% to 37%. Further, the doping concentration of the resonator in the filter ranges from 28.8% to 37%.
In the above embodiments of the present invention, it was explained that the upper limit value of the doping concentration of the piezoelectric layer of the resonator is selected based on the selected value of the layer thickness ratio E/P, so that Kt of the resonator can be ensured2The resonator has a large area while being stable. Furthermore, the lower limit value of the doping concentration of the piezoelectric layer of the resonator can be selected based on the selected value of the layer thickness ratio E/P, and a higher Q value of the resonator is ensured. The invention provides an effective guiding scheme for selecting the doping concentration of the doping element of the piezoelectric layer so as to obtain larger resonator area.
As can be understood by those skilled in the art, the material of the piezoelectric layer is not limited to aluminum nitride, but may be, for example, other piezoelectric materials listed in the present invention, and the doping element is not limited to scandium metal, but may be other dopable metal elements listed in the present invention. Although in the specific embodiment of the present invention, the example of doping scandium element with aluminum nitride is used to illustrate how to determine the upper limit value or the lower limit value of the doping concentration of the piezoelectric layer of the resonator based on the selected value of the layer thickness ratio E/P.
It is to be noted that, in the present invention, each numerical range, except when explicitly indicated as not including the end points, can be either the end points or the median of each numerical range, and all fall within the scope of the present invention.
As can be appreciated by those skilled in the art, bulk acoustic wave resonators can be used to form semiconductor devices other than filters.
Based on the above, the invention provides the following technical scheme:
1. a bulk acoustic wave resonator comprising:
a substrate;
an acoustic mirror;
a bottom electrode;
a piezoelectric layer comprising a doping element having a corresponding doping concentration; and
a top electrode is arranged on the top of the substrate,
wherein:
the resonance frequency of the resonator is higher than 2.5GHz, and the resonator has a layer thickness ratio E/P;
the resonator has an electromechanical coupling coefficient Kt2The doping concentration is less than a1, and the electromechanical coupling coefficient Kt is the layer thickness ratio E/P of 3 when a1 is2Corresponding doping concentration.
2. The resonator of claim 1, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and a1 is determined by the following formula:
Kt2＝0.2977a12+0.2085a1+0.033。
3. the resonator of claim 1, wherein:
the resonance frequency of the resonator is higher than 3.0 GHz;
the doping concentration is less than a2, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a2 is the thickness ratio E/P of the resonator layer is 2.82Corresponding doping concentration.
4. The resonator of claim 3, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and a3 is determined by the following formula:
Kt2＝0.3093a22+0.2149a2+0.0342。
5. the resonator of claim 3, wherein:
the resonance frequency of the resonator is higher than 3.5 GHz;
the doping concentration is less than a3, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a3 is the thickness ratio E/P of the resonator layer is 2.62Corresponding doping concentration.
6. The resonator of claim 5, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and a3 is determined by the following formula:
Kt2＝0.3437a32+0.2137a3+0.0364。
7. the resonator of claim 5, wherein:
the resonance frequency of the resonator is higher than 4 GHz;
the doping concentration is less than a4, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a4 is the thickness ratio E/P of the resonator layer is 2.42Corresponding doping concentration.
8. The resonator of claim 7, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and a4 is determined by the following formula:
Kt2＝0.3508a42+0.2213a4+0.0378。
9. the resonator of claim 7, wherein:
the resonance frequency of the resonator is higher than 4.5 GHz;
the doping concentration is less than a5, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a5 is the thickness ratio E/P of the resonator layer is 2.22Corresponding doping concentration.
10. The resonator of claim 9, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and a5 is determined by the following formula:
Kt2＝0.3345a52+0.2352a5+0.0399。
11. the resonator of claim 9, wherein:
the resonance frequency of the resonator is higher than 5 GHz;
the doping concentration is less than a6, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a6 is the thickness ratio E/P of the resonator layer is 22Corresponding doping concentration.
12. The resonator of claim 11, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and a6 is determined by the following formula:
Kt2＝0.407a62+0.2315a6+0.0421。
13. the resonator of claim 11, wherein:
the resonance frequency of the resonator is higher than 6 GHz;
the doping concentration is less than a7, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a7 is the thickness ratio E/P of the resonator layer is 1.82Corresponding doping concentration.
14. The resonator of claim 13, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and a7 is determined by the following formula:
Kt2＝0.4801a72+0.2157a7+0.0461。
15. the resonator of any of claims 1-14, wherein:
the doping concentration is not less than b1, and the electromechanical coupling coefficient Kt is obtained when the layer thickness ratio E/P of b1 is 0.752Corresponding doping concentration.
16. The resonator of claim 15, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and b1 is determined by the following formula:
Kt2＝0.3909b12+0.3056b1+0.062。
17. the resonator of claim 16, wherein:
the doping concentration is not less than b2, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the b2 is the thickness ratio E/P of the resonator layer is 0.852Corresponding doping concentration.
18. The resonator of claim 17, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and b2 is determined by the following formula:
Kt2＝0.4463b22+0.2869b2+0.0603。
19. the resonator of claim 17, wherein:
the doping concentration is not less than b3, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the b3 is the thickness ratio E/P of the resonator layer is 1.002Corresponding doping concentration.
20. The resonator of claim 19, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and b3 is determined by the following formula:
Kt2＝0.4147b32+0.2774b3+0.057。
21. a filter comprising a plurality of bulk acoustic wave resonators according to any of claims 1-20.
22. The filter of claim 21, wherein:
the filter is a filter with 2.515GHz-2.675GHz frequency band or 3.3GHz-3.6GHz frequency band; and is
The doping concentration of the resonators in the filter ranges from 14.4% to 26.5%.
23. The filter of claim 22, wherein:
the doping concentration of the resonators in the filter ranges from 15.7% to 26.5%.
24. The filter of claim 21, wherein:
the filter is a filter with a frequency band of 4.8GHz-4.96 GHz; and is
The doping concentration of the resonators in the filter ranges from 1% to 12.4%.
25. The filter of claim 24, wherein:
the doping concentration of the resonators in the filter ranges from 2.6% to 12.4%.
26. The filter of claim 21, wherein:
the filter is a filter with a frequency band of 5.15GHz-5.85 GHz; and is
The doping concentration of the resonators in the filter ranges from 28.5% to 37%.
27. The filter of claim 26, wherein:
the doping concentration of the resonators in the filter ranges from 28.8% to 37%.
28. A method for determining the doping concentration of a doping element of a piezoelectric layer of a bulk acoustic wave resonator having an electromechanical coupling coefficient Kt2The resonator has a resonant frequency higher than 2.5GHz and has a layer thickness ratio E/P, the method comprising the steps of:
selecting the doping concentration not less than a1 based on the layer thickness ratio E/P, wherein the doping concentration is 3 when a1 is the layer thickness ratio E/P of the resonatorCoefficient of electric coupling Kt2Corresponding doping concentration.
29. The method of claim 28, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and a1 is determined by the following formula:
Kt2＝0.2977a12+0.2085a1+0.033。
30. the method of claim 28, wherein:
the doping concentration is not less than b1, and the electromechanical coupling coefficient Kt is selected when b1 is the layer thickness ratio E/P of 0.752Corresponding doping concentration.
31. The method of claim 30, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and b1 is determined by the following formula:
Kt2＝0.3909b12+0.3056b1+0.062。
32. an electronic device comprising a filter according to any one of claims 21-27, or a bulk acoustic wave resonator according to any one of claims 1-20.
The electronic device includes, but is not limited to, intermediate products such as a radio frequency front end and a filtering and amplifying module, and terminal products such as a mobile phone, WIFI and an unmanned aerial vehicle.
Although embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
Claims (32)
1. A bulk acoustic wave resonator comprising:
a substrate;
an acoustic mirror;
a bottom electrode;
a piezoelectric layer comprising a doping element having a corresponding doping concentration; and
a top electrode is arranged on the top of the substrate,
wherein:
the resonance frequency of the resonator is higher than 2.5GHz, and the resonator has a layer thickness ratio E/P;
the resonator has an electromechanical coupling coefficient Kt2The doping concentration is less than a1, and the electromechanical coupling coefficient Kt is the layer thickness ratio E/P of 3 when a1 is2Corresponding doping concentration.
2. The resonator of claim 1, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and a1 is determined by the following formula:
Kt2＝0.2977a12+0.2085a1+0.033。
3. the resonator of claim 1, wherein:
the resonance frequency of the resonator is higher than 3.0 GHz;
the doping concentration is less than a2, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a2 is the thickness ratio E/P of the resonator layer is 2.82Corresponding doping concentration.
4. The resonator of claim 3, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and a3 is determined by the following formula:
Kt2＝0.3093a22+0.2149a2+0.0342。
5. the resonator of claim 3, wherein:
the resonance frequency of the resonator is higher than 3.5 GHz;
the doping concentration is less than a3, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a3 is the thickness ratio E/P of the resonator layer is 2.62Corresponding doping concentration.
6. The resonator of claim 5, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and a3 is determined by the following formula:
Kt2＝0.3437a32+0.2137a3+0.0364。
7. the resonator of claim 5, wherein:
the resonance frequency of the resonator is higher than 4 GHz;
the doping concentration is less than a4, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a4 is the thickness ratio E/P of the resonator layer is 2.42Corresponding doping concentration.
8. The resonator of claim 7, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and a4 is determined by the following formula:
Kt2＝0.3508a42+0.2213a4+0.0378。
9. the resonator of claim 7, wherein:
the resonance frequency of the resonator is higher than 4.5 GHz;
the doping concentration is less than a5, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a5 is the thickness ratio E/P of the resonator layer is 2.22Corresponding doping concentration.
10. The resonator of claim 9, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and a5 is determined by the following formula:
Kt2＝0.3345a52+0.2352a5+0.0399。
11. the resonator of claim 9, wherein:
the resonance frequency of the resonator is higher than 5 GHz;
the doping concentration is less than a6, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a6 is the thickness ratio E/P of the resonator layer is 22Corresponding doping concentration.
12. The resonator of claim 11, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and a6 is determined by the following formula:
Kt2＝0.407a62+0.2315a6+0.0421。
13. the resonator of claim 11, wherein:
the resonance frequency of the resonator is higher than 6 GHz;
the doping concentration is less than a7, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the a7 is the thickness ratio E/P of the resonator layer is 1.82Corresponding doping concentration.
14. The resonator of claim 13, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and a7 is determined by the following formula:
Kt2＝0.4801a72+0.2157a7+0.0461。
15. the resonator of any of claims 1-14, wherein:
the doping concentration is not less than b1, and the electromechanical coupling coefficient Kt is obtained when the layer thickness ratio E/P of b1 is 0.752Corresponding doping concentration.
16. The resonator of claim 15, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and b1 is determined by the following formula:
Kt2＝0.3909b12+0.3056b1+0.062。
17. the resonator of claim 16, wherein:
the doping concentration is not less than b2, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the b2 is the thickness ratio E/P of the resonator layer is 0.852Corresponding doping concentration.
18. The resonator of claim 17, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and b2 is determined by the following formula:
Kt2＝0.4463b22+0.2869b2+0.0603。
19. the resonator of claim 17, wherein:
the doping concentration is not less than b3, and the electromechanical coupling coefficient Kt is the electromechanical coupling coefficient when the b3 is the thickness ratio E/P of the resonator layer is 1.002Corresponding doping concentration.
20. The resonator of claim 19, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and b3 is determined by the following formula:
Kt2＝0.4147b32+0.2774b3+0.057。
21. a filter comprising a plurality of bulk acoustic wave resonators as claimed in any one of claims 1-20.
22. The filter of claim 21, wherein:
the filter is a filter with 2.515GHz-2.675GHz frequency band or 3.3GHz-3.6GHz frequency band; and is
The doping concentration of the resonators in the filter ranges from 14.4% to 26.5%.
23. The filter of claim 22, wherein:
the doping concentration of the resonators in the filter ranges from 15.7% to 26.5%.
24. The filter of claim 21, wherein:
the filter is a filter with a frequency band of 4.8GHz-4.96 GHz; and is
The doping concentration of the resonators in the filter ranges from 1% to 12.4%.
25. The filter of claim 24, wherein:
the doping concentration of the resonators in the filter ranges from 2.6% to 12.4%.
26. The filter of claim 21, wherein:
the filter is a filter with a frequency band of 5.15GHz-5.85 GHz; and is
The doping concentration of the resonators in the filter ranges from 28.5% to 37%.
27. The filter of claim 26, wherein:
the doping concentration of the resonators in the filter ranges from 28.8% to 37%.
28. A method for determining the doping concentration of a doping element of a piezoelectric layer of a bulk acoustic wave resonator having an electromechanical coupling coefficient Kt2The resonator has a resonant frequency higher than 2.5GHz and has a layer thickness ratio E/P, the method comprising the steps of:
selecting the doping concentration to be less than a1 based on the layer thickness ratio E/P, wherein a1 is the electromechanical coupling coefficient Kt when the layer thickness ratio E/P of the resonator is 32Corresponding doping concentration.
29. The method of claim 28, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and a1 is determined by the following formula:
Kt2＝0.2977a12+0.2085a1+0.033。
30. the method of claim 28, wherein:
the doping concentration is not less than b1, and the electromechanical coupling coefficient Kt is selected when b1 is the layer thickness ratio E/P of 0.752Corresponding doping concentration.
31. The method of claim 30, wherein:
the piezoelectric layer is an aluminum nitride layer doped with scandium, and b1 is determined by the following formula:
Kt2＝0.3909b12+0.3056b1+0.062。
32. an electronic device comprising a filter according to any one of claims 21-27 or a bulk acoustic wave resonator according to any one of claims 1-20.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114866058A (en) * | 2022-07-06 | 2022-08-05 | 深圳新声半导体有限公司 | Bulk acoustic wave filter based on Sc doping concentration change |
| CN115001428A (en) * | 2022-07-11 | 2022-09-02 | 深圳新声半导体有限公司 | Film concentration doping method for film filter |
| WO2022206332A1 (en) * | 2021-03-29 | 2022-10-06 | 诺思(天津)微系统有限责任公司 | Bulk acoustic resonator having tungsten electrode, filter, and electronic device |
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| CN109889177B (en) * | 2018-12-26 | 2023-04-07 | 天津大学 | Bulk acoustic wave resonator with doped isolation structure |
| CN111010131B (en) * | 2019-06-06 | 2024-09-17 | 天津大学 | Bulk acoustic wave resonator with doping concentration change, filter and electronic equipment |
| CN111030636A (en) * | 2019-07-15 | 2020-04-17 | 天津大学 | Bulk acoustic wave resonator with acoustic impedance mismatch structure, filter and electronic device |
| CN111010120A (en) * | 2019-09-20 | 2020-04-14 | 天津大学 | Bulk acoustic wave resonator, filter, and electronic device having adjustment layer |
| CN111313857A (en) * | 2019-11-29 | 2020-06-19 | 天津大学 | Bulk acoustic wave resonator, filter, and electronic device provided with insertion structure and temperature compensation layer |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2022206332A1 (en) * | 2021-03-29 | 2022-10-06 | 诺思(天津)微系统有限责任公司 | Bulk acoustic resonator having tungsten electrode, filter, and electronic device |
| CN114866058A (en) * | 2022-07-06 | 2022-08-05 | 深圳新声半导体有限公司 | Bulk acoustic wave filter based on Sc doping concentration change |
| CN115001428A (en) * | 2022-07-11 | 2022-09-02 | 深圳新声半导体有限公司 | Film concentration doping method for film filter |
| CN115001428B (en) * | 2022-07-11 | 2023-06-30 | 深圳新声半导体有限公司 | Film concentration doping method for film filter |
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