Acoustic wave resonator, filter and electronic device with temperature compensation layer

Abstract

The present invention provides an acoustic wave resonator, a filter, and an electronic device with a temperature compensation layer. A parameter, the electrode piezoelectric ratio, is introduced and a calculation method is provided. When the layers of the resonator are arranged so that the value of the electrode piezoelectric ratio meets certain conditions, the resonator can have better performance.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology, and in particular to an acoustic wave resonator and a filter with a temperature compensation layer, as well as electronic equipment. Background Art

[0002] An acoustic wave resonator is the fundamental unit of a bulk acoustic wave filter. Its basic structure consists of a piezoelectric film, a bottom electrode and a top electrode sandwiching the piezoelectric film, forming a piezoelectric stack. It also includes an acoustic reflection unit located beneath the bottom electrode. The overlapping area between the acoustic reflection unit, the bottom electrode, the top electrode, and the piezoelectric film forms the active operating area of ​​the acoustic wave resonator. When an RF signal is applied between the electrodes, the piezoelectric film vibrates due to the inverse piezoelectric effect, generating acoustic waves. The acoustic waves propagate perpendicular to the electrode surfaces and are reflected at the upper and lower interfaces.

[0003] Some acoustic wave resonators also have a temperature compensation layer. The temperature compensation layer is a layer or layers of material with a frequency temperature coefficient opposite to the sign of the piezoelectric layer itself (for example, aluminum nitride has a negative frequency temperature coefficient, while silicon dioxide has a positive frequency temperature coefficient) added to the stacked structure of the acoustic wave resonator. The temperature compensation layer offsets or partially offsets the resonator frequency drift caused by temperature changes. For a resonator with a temperature compensation layer and a specific frequency, different electromechanical coupling coefficients Kt can be obtained by adjusting the ratio of the upper and lower electrodes to the piezoelectric layer. Without changing the doping concentration of the piezoelectric layer, its Kt has a certain optimal range. Beyond this range, the quality factor Q value of the resonator will drop significantly. Therefore, a suitable way to adjust the layers of the acoustic wave resonator is needed to achieve the best possible performance. Summary of the Invention

[0004] In view of this, the present invention provides an acoustic wave resonator, a filter and an electronic device with a temperature compensation layer, wherein the acoustic wave resonator has better performance.

[0005] The present invention provides the following technical solutions:

[0006] An acoustic wave resonator with a temperature compensation layer, wherein the electrode piezoelectric ratio of the acoustic wave resonator is greater than 0.5, and the electrode piezoelectric ratio is calculated according to the following formula: electrode piezoelectric ratio = (e×TB+T2+n×T1) / T3; and: TB = T5+a×T4+b×T6+c×T7+d×T8; a=V / Va, b=V / Vb, c=V / Vc, d=V / Vd; wherein: T1 represents the thickness of the dielectric layer above the upper electrode of the acoustic wave resonator; T2 represents the thickness of the upper electrode of the acoustic wave resonator degree; T3 represents the thickness of the piezoelectric layer of the acoustic wave resonator; T4 represents the thickness of the middle electrode of the acoustic wave resonator; T5 represents the thickness of the bottom electrode of the acoustic wave resonator; T6 represents the thickness of the etch barrier layer of the temperature compensating layer of the acoustic wave resonator; T7 represents the thickness of the temperature compensating layer of the acoustic wave resonator; T8 represents the thickness of the seed layer of the acoustic wave resonator; the rates of influence of the middle electrode, the etch barrier layer, the temperature compensating layer and the seed layer of the acoustic wave resonator on the resonant frequency of the resonator are Va nm / MHz, Vbnm / MHz, Vc nm / MHz and Vd nm / MHz respectively; the rate of influence of the bottom electrode on the resonant frequency of the resonator is V nm / MHz; n=V2 / V1, e=V2 / V, where V1 represents the rate of influence of the thickness of the dielectric layer above the upper electrode on the resonant frequency of the resonator, and V2 represents the rate of influence of the thickness of the upper electrode on the resonant frequency of the resonator.

[0007] The dielectric layer above the top electrode, the middle electrode, the etch barrier layer of the temperature compensation layer, and the seed layer are optional. None of these layers can be provided, or only one or more of them can be provided. If a layer is missing, the calculation formula remains unchanged, and its thickness can be taken as 0 in the formula.

[0008] Optionally, the electrode piezoelectric ratio is less than 1.5.

[0009] Optionally, one or more of T1, T4, T6, and T8 are set to 0.

[0010] Optionally, the TB also satisfies the following relationship: TB=e×m(T2+n×T1), where m is 0.7 to 1.3.

[0011] A filter comprises the acoustic wave resonator described in the present invention.

[0012] An electronic device comprises the acoustic wave resonator or the filter of the present invention.

[0013] According to the technical solution of the present invention, a parameter such as the electrode piezoelectric ratio is introduced and a calculation method is given. When the arrangement of the layers of the resonator makes the value of the electrode piezoelectric ratio meet certain conditions, the resonator can have better performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] For purposes of illustration and not limitation, the present invention will now be described with reference to preferred embodiments thereof, particularly with reference to the accompanying drawings, in which:

[0015] Figure 1 is a schematic cross-sectional view of an acoustic wave resonator related to an embodiment of the present invention;

[0016] Figure 2 yes Figure 1 A partial enlarged schematic diagram (within the dotted box);

[0017] Figure 3 is a schematic cross-sectional view of another acoustic wave resonator related to an embodiment of the present invention;

[0018] Figure 4 is a schematic diagram of the relationship between the piezoelectric ratio and the Q value of the electrode according to an embodiment of the present invention;

[0019] Figure 5 This is a curve related to an embodiment of the present invention in which Sc is doped into AlN to change Kt when the electrode piezoelectric ratio is 1. DETAILED DESCRIPTION

[0020] The embodiments of the present invention are described below with reference to the accompanying drawings. Figure 1 is a schematic cross-sectional view of an acoustic wave resonator related to an embodiment of the present invention; Figure 2 yes Figure 1 A magnified schematic diagram of a part (within the dotted box). Figure 1 and Figure 2 The description of each part is as follows:

[0021] 10: Substrate, optional materials include single crystal silicon, gallium arsenide, sapphire, quartz, etc.

[0022] 20: Acoustic mirror, which can be a cavity, a Bragg reflector layer or other equivalent forms. This paper uses a cavity;

[0023] 30: Bottom electrode, the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or their alloys;

[0024] 40: Interlayer electrode or middle electrode, the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or the composite of the above metals or their alloys;

[0025] 50: The piezoelectric layer can be a single crystal piezoelectric material, such as single crystal aluminum nitride, single crystal gallium nitride, single crystal lithium niobate, single crystal lead zirconate titanate (PZT), single crystal potassium niobate, single crystal quartz film, or single crystal lithium tantalate, etc. It can also be a polycrystalline piezoelectric material (corresponding to single crystal, non-single crystal material), such as polycrystalline aluminum nitride, zinc oxide, PZT, etc., and can also be a rare earth element doped with a certain atomic ratio of the above materials. The material may be, for example, doped aluminum nitride 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), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), etc.;

[0026] 60: Upper electrode, the material of which can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium or a composite of the above metals or their alloys;

[0027] 70: dielectric layer above the upper electrode, the material can be AlN, SiN, SiO2, etc.;

[0028] 80: Etching barrier layer of the temperature compensation layer, which can be made of aluminum nitride, zinc oxide, PZT and other materials and contains rare earth element doping materials with a certain atomic ratio of the above materials;

[0029] 81: Temperature compensation layer, optional SiO2, other positive temperature coefficient materials;

[0030] 82: Seed layer, which can be made of aluminum nitride, zinc oxide, PZT and other materials and contains rare earth element doping materials with a certain atomic ratio of the above materials.

[0031] In this embodiment, a parameter called electrode piezoelectric ratio is introduced and the corresponding calculation method is given. For the convenience of description, the relevant parameters are first explained. Figure 1 and Figure 2 The meaning of the parameters of each layer thickness (unit: nanometer) are as follows:

[0032] T1: thickness of the dielectric layer 70 above the upper electrode;

[0033] T2: thickness of the upper electrode 60;

[0034] T3: thickness of the piezoelectric layer 50;

[0035] T4: thickness of the intermediate electrode 40;

[0036] T5: thickness of the bottom electrode 30;

[0037] T6: thickness of the etch stop layer 80 of the temperature compensation layer;

[0038] T7: thickness of the temperature compensation layer 81;

[0039] T8: thickness of the seed layer 82 .

[0040] The coefficients a, b, c, and d are introduced: a = V / Va, b = V / Vb, c = V / Vc, and d = V / Vd. Here, Va, Vb, Vc, and Vd are the rates of influence of the middle electrode 40 of the acoustic wave resonator, the etching barrier layer 80 of the temperature compensation layer, the temperature compensation layer 81, and the seed layer 82 on the resonant frequency of the resonator, respectively, with the unit being nm / MHz (nanometers per megahertz). V (nm / MHz) represents the rate of influence of the bottom electrode 30 on the resonant frequency of the resonator. Parameters n and e are also introduced: n = V2 / V1, and e = V2 / V, where V1 represents the rate of influence of the thickness of the dielectric layer 70 above the upper electrode on the resonant frequency of the resonator, and V2 represents the rate of influence of the thickness of the upper electrode 60 on the resonant frequency, with the unit being nm / MHz.

[0041] Finally, the electrode piezoelectric ratio is calculated based on the above parameters and coefficients. To simplify the expression, the intermediate parameter TB is added: TB = T5 + a × T4 + b × T6 + c × T7 + d × T8. The final electrode piezoelectric ratio is calculated according to the following formula: Electrode piezoelectric ratio = (e × TB + T2 + n × T1) / T3.

[0042] By selecting an appropriate electrode piezoelectric ratio, better resonator performance can be achieved. The following example illustrates this. Figure 3 FIG2 is a schematic cross-sectional view of another acoustic wave resonator according to an embodiment of the present invention, in which a raised structure 90 is added above the piezoelectric layer. The material may be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or a combination of these metals or their alloys. An air gap 91 exists between raised structure 90 and piezoelectric layer 50. Figure 3 The local enlarged structure of the etch stop layer 80, the temperature compensating layer 81 and the seed layer 82 of the temperature compensating layer can be seen in Figure 2 .

[0043] Figure 3 The experimental results of the 2GHz frequency band corresponding to the structure shown are as follows Figure 4 As shown, Figure 4 3 is a schematic diagram of the relationship between the piezoelectric ratio of electrodes and the Q value according to an embodiment of the present invention. The multiple horizontal values ​​in the figure represent the width d of the protruding structure 90, and the vertical value represents the change trend of the Q value.

[0044] according to Figure 4As shown in the figure, when the electrode piezoelectric ratio is 0.5, the Q value decreases significantly at the first peak as the width d of the protrusion structure 90 changes. When the electrode piezoelectric ratio is 1.5, the Q value decreases slightly at the first peak, but the decrease is not significant. When the electrode piezoelectric ratio is 1, there is a peak when the protrusion structure d is 1um, and the Q value first increases and then decreases, while the other two ratios do not show this trend. The reason for this situation is the imbalance of the electrode piezoelectric ratio. When the electrode piezoelectric ratio is 1, it is optimal. When this ratio is less than 0.5, the performance of the resonator will be severely degraded.

[0045] Sometimes, for a given frequency, in order to obtain the target Kt, the electrode piezoelectric ratio must be adjusted within a certain range to meet the requirements. However, the principle is that the ratio must comply with the above ratio limit. If it exceeds the range, other methods must be used to solve it. For example, Sc doping can be introduced. By selecting the appropriate doping concentration at the appropriate ratio, the desired Kt can be obtained.

[0046] For example, at 2GHz frequency, under the condition of meeting specific temperature drift (0 temperature drift), the resonator can obtain a Kt of 2.1% to 4.2% without doping. However, when it is necessary to achieve a Kt greater than 4.2%, doping is required. By selecting an appropriate doping concentration, a resonator with a relatively high Q value can be obtained while meeting the Kt requirement of 0.5 < electrode piezoelectric ratio = (e×TB+T2+n×T1) / T3 < 1.5, such as Figure 5 , Figure 5 The embodiment of the present invention is related to the curve of changing Kt by doping Sc in AlN when the electrode piezoelectric ratio is 1. Figure 5 It can be seen that by changing the doping ratio, the Kt can be changed while maintaining the electrode piezoelectric ratio, thus meeting the performance requirements and obtaining the desired Kt.

[0047] According to the technical solution of the embodiments of the present invention, a parameter, the electrode piezoelectric ratio, is introduced and a calculation method is provided. When the configuration of the resonator layers ensures that the value of this parameter meets certain conditions, the resonator can achieve good performance. Application of this resonator in filters or other electronic devices can also help improve the performance of the device or equipment.

[0048] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. An acoustic wave resonator with a temperature compensation layer, characterized in that: The piezoelectric ratio of the electrodes of the acoustic wave resonator is greater than 0.

5. The piezoelectric ratio of the electrode is calculated according to the following formula: Electrode piezoelectric ratio = (e×TB+T2+n×T1) / T3; and: TB=T5+a×T4+b×T6+c×T7+d×T8; a=V / Va, b=V / Vb, c=V / Vc, d=V / Vd; in: T1 represents the thickness of the dielectric layer above the upper electrode of the acoustic wave resonator; T2 represents the thickness of the upper electrode of the acoustic wave resonator; T3 represents the thickness of the piezoelectric layer of the acoustic wave resonator; T4 represents the thickness of the middle electrode of the acoustic wave resonator; T5 represents the thickness of the bottom electrode of the acoustic wave resonator; T6 represents the thickness of the etching barrier layer of the temperature compensation layer of the acoustic wave resonator; T7 represents the thickness of the temperature compensation layer of the acoustic wave resonator; T8 represents the thickness of the seed layer of the acoustic wave resonator; The middle electrode of the acoustic wave resonator, the etching barrier layer of the temperature compensation layer, the temperature compensation layer, and the seed layer each have an influence rate on the resonant frequency of the resonator of Va nm / MHz, Vb nm / MHz, Vc nm / MHz, and Vd nm / MHz respectively; The rate of influence of the bottom electrode on the resonant frequency of the resonator is V nm / MHz; n = V2 / V1, e = V2 / V, where V1 represents the rate at which the thickness of the dielectric layer above the upper electrode affects the resonant frequency of the resonator, and V2 represents the rate at which the thickness of the upper electrode affects the resonant frequency of the resonator, in nm / MHz. The resonator performance can be tuned by selecting the piezoelectric ratio of the electrodes.

2. The acoustic wave resonator according to claim 1, characterized in that The electrode piezoelectric ratio is less than 1.

5.

3. The acoustic wave resonator according to claim 1 or 2, characterized in that One or more of T1, T4, T6, and T8 is 0.

4. The acoustic wave resonator according to claim 1 or 2, characterized in that The TB also satisfies the following relationship: TB=e×m(T2+n×T1), where m ranges from 0.7 to 1.

3.

5. A filter, characterized in that: The invention comprises the acoustic wave resonator according to any one of claims 1 to 4.

6. An electronic device, characterized in that: The method comprises the acoustic wave resonator according to any one of claims 1 to 4, or the filter according to claim 5.

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