WO2021159882A1 - 压电滤波器及其质量负载实现方法和含压电滤波器的装置 - Google Patents

压电滤波器及其质量负载实现方法和含压电滤波器的装置 Download PDF

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WO2021159882A1
WO2021159882A1 PCT/CN2020/141269 CN2020141269W WO2021159882A1 WO 2021159882 A1 WO2021159882 A1 WO 2021159882A1 CN 2020141269 W CN2020141269 W CN 2020141269W WO 2021159882 A1 WO2021159882 A1 WO 2021159882A1
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resonator
series
compensation layer
parallel
temperature compensation
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PCT/CN2020/141269
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French (fr)
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庞慰
郑云卓
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诺思(天津)微系统有限责任公司
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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
    • H03H9/46—Filters
    • H03H9/54—Filters comprising resonators of piezoelectric or electrostrictive material

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  • the present invention relates to the technical field of microelectronics, to a piezoelectric filter and a method for realizing a mass load thereof, and a device containing a piezoelectric filter, and in particular to a method for realizing a mass load of a piezoelectric filter, a piezoelectric filter, and a duplexer , High-frequency front-end circuit and communication device.
  • the small-size filter devices that can meet the use of communication terminals are mainly piezoelectric acoustic wave filters.
  • the resonators that constitute this type of acoustic wave filter mainly include: FBAR (Film Bulk Acoustic Resonator), SMR (Solidly Mounted Resonator, solid-state assembly resonator) and SAW (Surface Acoustic Wave, surface acoustic wave resonator).
  • the filters manufactured based on the principle of bulk acoustic wave FBAR and SMR (collectively referred to as BAW, bulk acoustic wave resonator) have the advantages of lower insertion loss and faster roll-off characteristics compared to filters manufactured based on the principle of surface acoustic wave SAW. .
  • the piezoelectric materials and metal materials constituting the acoustic wave resonator both have the characteristics of negative temperature coefficient, that is, when the temperature increases, the resonant frequency of the resonator will move in a certain proportion to the low frequency direction (temperature drift).
  • the temperature coefficient of SAW is -35ppm/°C ⁇ -50ppm/°C
  • the temperature coefficient of BAW is -25ppm/°C ⁇ -30ppm/°C.
  • a common solution is to add a material that can realize the temperature compensation effect in the resonator.
  • this temperature compensation material is often selected as silicon dioxide, mainly because silicon dioxide has a positive temperature coefficient that is just the opposite of most materials. The price is suitable for mass production applications.
  • This type of temperature-compensated material resonator also known as TCF resonator, is a component unit of the temperature-compensated filter.
  • the introduction of a temperature compensation layer in the resonator is not without cost. It makes the characteristics of the resonator worse, which is mainly reflected in the increase of the resonator loss and the decrease of the electromechanical coupling coefficient. As the loss of the resonator increases, the insertion loss of the filter increases, thereby increasing the loss in the RF link and deteriorating the transceiver performance of the RF front-end. The electromechanical coupling coefficient becomes smaller, and the distance between the series resonant frequency and the parallel resonant frequency of the resonator is reduced. The roll-off characteristics of the filter may be improved, but at the same time the bandwidth of the filter will also be narrowed. In most communication systems, The bandwidth of the filter is proposed according to the system requirements, and the bandwidth cannot be narrowed indefinitely.
  • the present invention provides a method for realizing the mass load of a piezoelectric filter, a piezoelectric filter, a duplexer, a high-frequency front-end circuit, and a communication device to solve the technical problems in the prior art.
  • a method for realizing the mass load of a piezoelectric filter is provided.
  • the piezoelectric filter includes a series branch and a parallel branch, and the series branch includes more than three input and output connected in series with the piezoelectric filter.
  • the bulk acoustic wave resonator between the terminals, a parallel circuit is set between the connection point of the adjacent resonators and the ground terminal.
  • the temperature compensation layer of the resonator is used as the mass load, and all series resonators are For the same resonator, each series resonator has or does not have a temperature compensation layer; all parallel resonators have a temperature compensation layer and are thicker than the temperature compensation layer of the series resonator.
  • the parallel resonator adopts zero temperature drift and low Kt 2 temperature compensation
  • the resonator can effectively improve the roll-off characteristics on the left side of the filter.
  • the thickness of the temperature compensation layer of the parallel resonator satisfies the following condition: the positive temperature drift effect generated by the temperature compensation layer offsets the negative temperature drift effect of other layers of the parallel resonator, so that the The temperature coefficient of the parallel resonator is within the neighborhood of the specified range of 0ppm/°C.
  • the thickness of the temperature compensation layer of the parallel resonator further satisfies the following condition: the mass loading effect generated by the thickness of the temperature compensation layer of the parallel resonator makes the series resonance frequency of the series resonator and the temperature compensation layer added The difference between the parallel resonant frequencies of the subsequent parallel resonators is within a preset range.
  • the method further includes: adjusting the thickness of one or more of the upper electrode, the lower electrode, the piezoelectric layer, and the temperature compensation layer of the parallel resonator so that the temperature coefficient of the parallel resonator is 0 ppm/°C And adjust the thickness of one or more of the upper electrode, lower electrode, piezoelectric layer, and temperature compensation layer of the series resonator so that the temperature coefficient of the series resonator is within one Within the neighborhood of the preset range of the specified value less than 0 ppm/°C, to adjust the roll-off performance of the filter.
  • a piezoelectric filter is provided.
  • the piezoelectric filter of the present invention includes a series branch and a parallel branch.
  • the series branch includes three or more bulk acoustic wave resonators connected in series between the input and output ends of the piezoelectric filter.
  • a parallel circuit is set between the connection point and the ground terminal, all series resonators are the same resonator, each series resonator has or does not have a temperature compensation layer; all parallel resonators have a temperature compensation layer and have a thickness greater than the series The temperature compensation layer of the resonator.
  • the thickness of the temperature compensation layer of the parallel resonator satisfies the following condition: the positive temperature drift effect generated by the temperature compensation layer offsets the negative temperature drift effect of other layers of the parallel resonator, so that the The temperature coefficient of the parallel resonator is within the neighborhood of the specified range of 0ppm/°C.
  • the thickness of the temperature compensation layer of the parallel resonator further satisfies the following condition: the mass loading effect generated by the thickness of the temperature compensation layer of the parallel resonator makes the series resonance frequency of the series resonator and the temperature compensation layer added The difference between the parallel resonant frequencies of the subsequent parallel resonators is within a preset range.
  • a duplexer including the piezoelectric filter according to the present invention.
  • a high-frequency front-end circuit includes the piezoelectric filter of the present invention.
  • a communication device including the piezoelectric filter according to the present invention.
  • Figure 1A is the electrical symbol of BAW, and Figure 1B is the equivalent electrical model diagram of BAW;
  • Figure 2 is a schematic diagram of the relationship between resonator impedance and fs, fp;
  • Figure 3 is a schematic diagram of a traditional ordinary resonator
  • Figure 4 is a schematic diagram of a temperature compensated resonator
  • Figure 5 is a schematic diagram of the performance comparison of the resonator before and after the temperature compensation layer is added;
  • Fig. 6 is a circuit diagram of a piezoelectric filter 100 according to an embodiment of the present invention.
  • FIG. 7 is a circuit diagram of the piezoelectric filter 001 of the first comparative example
  • FIG. 8A is a schematic diagram of the impedance-frequency relationship of the series-parallel resonator of the piezoelectric filter 001
  • FIG. 8B is a schematic diagram of the impedance-frequency relationship of the series-parallel resonator of the piezoelectric filter 100;
  • FIG. 9A is a schematic diagram of comparing the amplitude-frequency curves of the piezoelectric filter 100 and the piezoelectric filter 001, and FIG. 9B is a partial enlarged view of FIG. 9A;
  • FIG. 10A is a schematic diagram of the three-temperature curve of the piezoelectric filter 001 at low temperature, normal temperature, and high temperature
  • FIG. 10B is a partial enlarged view of FIG. 10A;
  • FIG. 11A is a schematic diagram of the three-temperature curve of the piezoelectric filter 100 at low temperature, normal temperature, and high temperature
  • FIG. 11B is a partial enlarged view of FIG. 11A;
  • Figure 12 is a circuit diagram of a second comparative piezoelectric filter 002;
  • FIG. 13A is a schematic diagram of the impedance-frequency relationship of the series-parallel resonator of the piezoelectric filter 002
  • FIG. 13B is a schematic diagram of the impedance-frequency relationship of the series-parallel resonator of the piezoelectric filter 100;
  • FIG. 14A is a schematic diagram of comparing the amplitude-frequency curves of the piezoelectric filter 100 and the piezoelectric filter 002, and FIG. 14B is a partial enlarged view of FIG. 14A;
  • 15 is a schematic diagram of the structure of a filter according to an embodiment of the present invention, in which both the series filter and the parallel filter have a temperature compensation layer.
  • Figure 1A is the electrical symbol of the piezoelectric acoustic wave resonator
  • Figure 1B is its equivalent electrical model diagram.
  • the electrical model is simplified to a resonant circuit composed of L m , C m and C 0.
  • the resonant circuit has two resonant frequencies: one is f s when the impedance of the resonant circuit reaches the minimum value, and f s is defined as the series resonant frequency of the resonator; the other is when the impedance of the resonant circuit value reaches a maximum when f p, f p defines the parallel resonant frequency for the resonator.
  • Kt 2 eff (hereinafter abbreviated as Kt 2 ) of the resonator is defined, which can be expressed by f s and f p :
  • Figure 2 shows the relationship between the impedance of the resonator and f s and f p.
  • the greater the effective electromechanical coupling coefficient the greater the frequency difference between f s and f p , that is, the farther the two resonance frequency points are separated.
  • the impedance amplitude of the resonator at f s is defined as R s , which is the minimum value in the impedance curve of the resonator;
  • the impedance amplitude of the resonator at f p is defined as R p , which is the resonator
  • R s and R p are important parameters for describing resonance loss characteristics. When R s is smaller and R p is larger, the loss of the resonator is smaller, the Q value is higher, and the insertion loss characteristics of the filter are also better.
  • FIG. 3 is a schematic diagram of a conventional common resonator.
  • the resonator is fabricated on the substrate 104, and the bottom electrode 102 and the top electrode 101 are metal electrodes, and the thickness is usually several hundred nanometers.
  • the piezoelectric material film 103 usually uses zinc oxide or aluminum nitride, and has a thickness of several hundred nanometers to several micrometers.
  • the sound waves need to be reflected on the surface of the top and bottom electrodes.
  • Above the top electrode 101 is air capable of forming sound waves.
  • an air cavity 100 is formed under the bottom electrode 102.
  • the piezoelectric material film 103 When an alternating voltage is applied to the top electrode 101 and the bottom electrode 102, the piezoelectric material film 103 is excited to generate a piezoelectric effect to generate mechanical sound waves.
  • the sound wave propagates and reflects between the top and bottom electrodes, forming a standing wave resonance, and then forming a resonance in the electrical response. Due to the use of a cavity to form reflections, this type of resonator is called a cavity-reflective bulk acoustic wave resonator.
  • FIG. 4 is a schematic diagram of a temperature compensated resonator.
  • the temperature-compensated resonator may include: a top electrode 201, a bottom electrode 202, a piezoelectric layer 203, a substrate 204, a temperature compensation layer 205 located inside the bottom electrode 202, and an air cavity 200, which can be regarded as based on FIG. 3 FBAR resonator with temperature compensation layer added.
  • the material of the temperature compensation layer 205 is generally silicon dioxide, and its pattern is smaller than or equal to the bottom electrode pattern, that is to say, the compensation layer and the bottom electrode look like sandwich biscuits or sandwiches.
  • the temperature compensation layer 205 is completely encapsulated in the bottom electrode material.
  • the advantage of this production is that it can be effectively protected from damage by other manufacturing processes.
  • the electrode materials above and below the temperature compensation layer are connected together at the edges, the formation of a parasitic capacitance composed of the three is avoided, which greatly deteriorates the Kt 2 and loss characteristics of the resonator.
  • the ratio of the layout area of the temperature compensation layer to the layout area of the top layer of the bottom electrode or the bottom layer of the bottom electrode is 0.5-1.
  • Figures 5A and 5B are comparisons of the impedance curves of the resonator before and after the temperature compensation layer is added to the resonator.
  • the Kt 2 of the resonator is reduced from 6.5% to 3.4%
  • R s is increased from 0.66 ohms to 1.37 ohms
  • Rp is reduced from 2592 ohms to 1314 ohms.
  • the temperature coefficient of the resonator has changed from -25ppm/°C ⁇ -30ppm/°C to about 0ppm/°C.
  • Kt 2 will be about half of the original value
  • R s will be increased to about twice of the original value
  • R p will be reduced to about half of the original value
  • the loss of the resonator will increase by a certain amount.
  • the Q value is reduced.
  • the first aspect of the present invention provides a method for realizing the mass load of a piezoelectric filter.
  • the piezoelectric filter includes a series branch and a parallel branch.
  • the series branch includes three or more connected in series at the output end of the piezoelectric filter.
  • a parallel circuit is set between the connection point of the adjacent resonator and the ground terminal.
  • the temperature compensation layer of the resonator is used as the mass load, and all series resonators are the same Resonators, each series resonator has or does not have a temperature compensation layer; all parallel resonators have a temperature compensation layer and have a thickness greater than that of the series resonator.
  • the thickness of the temperature compensation layer in the series resonator is zero, so the thickness difference of the temperature compensation layer of the series-parallel resonator is equal to the thickness of the temperature compensation layer in the parallel resonator. It should also be noted that when the series resonators are the same temperature-compensated resonator, and the thickness of the temperature compensation layer of the series resonator is smaller than the thickness of the temperature compensation layer of the parallel resonator, there is a difference in the thickness of the temperature compensation layer of the series resonator to ensure Realizing the series-parallel frequency difference is to realize the load effect.
  • the temperature coefficient of the series resonator is zero. This means that the positive temperature drift effect produced by the temperature compensation layer can exactly offset the negative temperature drift effects of all other layers, so that the parallel resonator becomes a temperature compensation resonator with a temperature coefficient equal to 0 ppm/°C.
  • a temperature coefficient of zero means that the temperature drift effect of the temperature compensation layer exactly offsets the temperature drift effect of other layers, so that the piezoelectric filter has stable electrical performance under different ambient temperatures.
  • the thickness of the temperature compensation layer of the parallel resonator is equivalent to the mass load effect, so that the parallel resonant frequency of the parallel resonator after the temperature compensation layer is added is equal to the series resonant frequency of the series resonator.
  • the thickness of the temperature compensation layer is exactly equal to the mass load effect, so that the parallel resonant frequency of the parallel resonator after the temperature compensation layer is added is almost equal to the series resonant frequency of the series resonator without the temperature compensation layer, thus forming a filter Characteristic curve.
  • the second aspect of the present invention provides a piezoelectric filter, which includes a series branch and a parallel branch.
  • the series branch includes three or more bulk acoustic wave resonators connected in series between the output ends of the piezoelectric filter, and adjacent resonators
  • a parallel circuit is set between the connection point and the ground terminal, characterized in that all series resonators are the same resonator, and each series resonator has or does not have a temperature compensation layer; all parallel resonators have a temperature compensation layer and The thickness is greater than the temperature compensation layer of the series resonator.
  • the temperature coefficient of the series resonator is zero.
  • the thickness of the temperature compensation layer of the parallel resonator is equivalent to the mass load effect, so that the parallel resonant frequency of the parallel resonator after the temperature compensation layer is added is equal to the series resonant frequency of the series resonator.
  • the piezoelectric filter of the embodiment of the present invention has obvious advantages in performance, whether it is a filter that is all ordinary FBAR resonators or a filter that is all temperature-compensated resonators, and takes into account the roll-off on the left side. And the better choice of passband insertion loss performance.
  • the piezoelectric filter of the embodiment of the present invention is listed below for performance comparison with two other piezoelectric filters.
  • the piezoelectric filter 100 has a circuit diagram as shown in FIG. 6 and includes 5 series resonators and 4 parallel resonators. All the parallel resonators are temperature-compensated resonators as shown in Fig. 4, and all series resonators are ordinary FBAR resonators as shown in Fig. 3.
  • the passband frequency range of this filter is 2565MHz ⁇ 2595MHz, the passband bandwidth is 30MHz, and requires more than 45dB out-of-band suppression at 2540MHz.
  • piezoelectric filter 001 Its circuit diagram is shown in Figure 7, including 5 series common resonators and 4 parallel common resonators.
  • the piezoelectric filter 001 is composed of a series resonator and a parallel resonator in a ladder-like cascade structure, and a mass load layer is added to the parallel resonator.
  • the material is the same as the electrode material of the BAW device, making it parallel resonant
  • the frequency is basically the same as the resonant frequency of the series resonator, thus forming the curve characteristic of the filter.
  • FIG. 8A is a schematic diagram of the impedance-frequency relationship of the series-parallel resonator of the piezoelectric filter 001
  • FIG. 8B is a schematic diagram of the impedance-frequency relationship of the series-parallel resonator of the piezoelectric filter 100.
  • the comparison of the two figures shows that the filter requires more than 45dB of out-of-band suppression at 2540MHz.
  • the series resonance frequency of the parallel resonator in the piezoelectric filter 100 of the embodiment and the piezoelectric filter 001 of the first comparative example are both set at 2530MHz.
  • the parallel resonator in the embodiment is a temperature-compensated resonator with a relatively small Kt2, and the distance between fs and fp is smaller, the series resonant frequency of the series resonator in the embodiment is compared with the first comparison
  • the regular meeting is obviously low, which is to ensure the impedance matching characteristics of the filter in the passband range.
  • FIG. 9A is a schematic diagram of comparing the amplitude-frequency curves of the piezoelectric filter 100 (solid line) and the piezoelectric filter 001 (dashed line), and FIG. 9B is a partial enlarged view of FIG. 9A.
  • the piezoelectric filter 001 uses ordinary FBAR resonators, its Kt2 is about 6.5%, and the bandwidth of the filter is relatively wide.
  • the insertion loss of the filter at 2565MHz is about 3.2dB.
  • the passband is wider, the insertion loss on the right side of the passband can reach nearly 1.0dB, and the fluctuation value in the 30MHz passband is relatively large. Big.
  • the parallel resonator of the embodiment adopts a temperature-compensated resonator, and its Kt2 is about 3.4%, and the frequency range of the transition from the minimum impedance to the maximum impedance is smaller, so that better left-side roll-off characteristics can be achieved.
  • the zero temperature drift characteristic of the parallel resonator also makes the roll-off edge on the left side of the filter change little with temperature changes, which further increases the margin of the filter roll-off.
  • Fig. 10A is a schematic diagram of the three-temperature curve of the piezoelectric filter 001 at low temperature, normal temperature, and high temperature
  • Fig. 10B is a partial enlarged view of Fig. 10A.
  • the black solid line is the curve at room temperature, because all the resonators used have a temperature coefficient of -25ppm/°C ⁇ -30ppm/°C, so compared with the curve at room temperature, the amplitude-frequency curve of the filter at low temperature is in the direction of high frequency Moving, the insertion loss becomes better at the same time, and the amplitude-frequency curve moves to the low frequency direction at high temperature, and the insertion loss becomes worse at the same time.
  • FIG. 11A is a schematic diagram of the three-temperature curve of the piezoelectric filter 100 at low temperature, normal temperature, and high temperature
  • FIG. 11B is a partial enlarged view of FIG. 11A.
  • the black solid line is the curve at room temperature, because the series resonator is an ordinary resonator with a temperature coefficient of -25ppm/°C ⁇ -30ppm/°C, while the parallel resonator is a temperature-compensated resonator with a temperature coefficient of 0ppm/°C Therefore, compared with the normal temperature curve, the filter moves to the high frequency direction along the right side of the amplitude-frequency curve at low temperature, and the insertion loss becomes better at the same time, while the right side of the amplitude-frequency curve moves to the low frequency direction at high temperature, and the insertion loss becomes worse.
  • the right edge of the filter is anchored by the zero temperature drift characteristic of the temperature-compensated resonator, and the sub-surface frequency position changes very little, thereby improving the roll
  • a filter with only a temperature compensation layer added to the parallel resonator has the following advantages compared to an ordinary piezoelectric filter without a temperature compensation layer:
  • the parallel resonator adopts a temperature- compensated resonator with zero temperature drift and small Kt 2 , which can effectively improve the roll-off characteristics on the left side of the filter.
  • FIG. 13A is a schematic diagram of the impedance-frequency relationship of the series-parallel resonator of the piezoelectric filter 002
  • FIG. 13B is a schematic diagram of the impedance-frequency relationship of the series-parallel resonator of the piezoelectric filter 100. It can be seen that the piezoelectric filter 002 has a small Kt 2 , The characteristics of large loss and zero temperature drift.
  • Fig. 14A is a comparison of the amplitude-frequency curves of the piezoelectric filter 100 (solid line) and the piezoelectric filter 002 (dashed line), and Fig. 14B is a partial enlarged view of Fig. 14A.
  • the piezoelectric filter 002 uses temperature-compensated resonators, its Kt 2 is about 3.4%, and the loss is relatively large, so the bandwidth of the filter is narrow, the insertion loss at 2565MHz is about 3.6dB, and the insertion loss at 2595MHz is about 3.6dB. The loss is about 2.6dB, and the overall in-band insertion loss in the passband is about 0.35dB worse than the embodiment.
  • the piezoelectric filter 002 all adopts temperature-compensated resonators, the temperature drift characteristics of the roll-off edges on the left and right sides are good, but the loss in bandwidth and insertion loss is relatively large, which cannot meet the application requirements of the filter.
  • the piezoelectric filter of the embodiment of the present invention has the following Advantages: (1) The temperature compensation layer is used as the mass load, eliminating the need for additional process steps to make the mass load; (2) The series resonator uses an ordinary resonator instead of a temperature-compensated resonator, and the resonator loss is relatively good, thereby improving The insertion loss characteristics of the filter are improved; (3) The series resonator adopts an ordinary resonator instead of a temperature-compensated resonator, which appropriately reduces the effect of reducing the Kt 2 of the temperature-compensated resonator on the bandwidth of the filter.
  • Fig. 15 is a schematic diagram of a structure of a filter according to an embodiment of the present invention.
  • the circuit diagram of the FBAR filter 300 shown in FIG. 15 is the same as that of FIG. 11, and both series and parallel connections are temperature-compensated resonators.
  • the figure shows the cavity made on the substrate, the bottom electrode, the piezoelectric layer, the top electrode, and the temperature compensation layer wrapped around the bottom electrode and located in the resonance region.
  • a passivation layer is usually formed above the upper electrode. Its material can be a relatively stable non-metallic material, such as silicon dioxide. It is even possible to use the same material as the piezoelectric layer, such as aluminum nitride.
  • the resonator on the left in FIG. 15 is a series resonator, the resonator on the right is a parallel resonator, and the resonators in the other filters are not shown.
  • the thickness of the temperature compensation layer of the series resonator is t1
  • the thickness of the temperature compensation layer of the parallel resonator is t2
  • t1 and t2 satisfy the relationship, t2>t1
  • the thickness difference between the two forms the frequency difference between the parallel resonator and the series resonance , That is, the mass loading effect required by the filter design.
  • the thickness of the other layers of the series resonator and the parallel resonator are the same.
  • this figure shows the thickness of each layer in more detail than the previous resonator. Because the thickness of the temperature compensation layer is different, the film The oblique angle of the boundary formed during the deposition process. In this embodiment, since the thickness of the temperature compensation layer of the series and parallel resonators is different, and the other layers are the same, the temperature coefficients of the two resonators must be different. In the design process, you can select a suitable stack according to the characteristics of the electrical performance of the filter, so that the temperature coefficient of the corresponding position is closer to 0ppm/°C.
  • each layer can be designed so that the temperature coefficient of the parallel resonator is about 0ppm/°C, while the temperature coefficient of the series resonator can be farther away than 0ppm/°C , Such as -10ppm.
  • the filter formed in this way can get better left side roll-off, and at the same time, the right side roll-off will have a certain improvement compared with the filter without temperature-compensated resonator.
  • the piezoelectric filter of the embodiment of the present invention has obvious advantages in performance, whether it is a filter that is all ordinary FBAR resonators or a filter that is all temperature-compensated resonators. A better choice for roll-off and passband insertion loss performance.

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Abstract

一种实现压电滤波器（100）质量负载的方法、压电滤波器（100）、双工器、高频前端电路以及通信装置。该方法中，所述压电滤波器（100）包括串联支路和并联支路，所述串联支路包括三个以上串联在所述压电滤波器（100）的输入输出端之间的体声波谐振器，相邻谐振器的连接点与接地端之间设置有并联电路，在该方法中，将谐振器的温度补偿层（205）作为质量负载，并且：所有串联谐振器均为相同的谐振器，各串联谐振器具有或不具有温度补偿层（205）；所有并联谐振器均具有温度补偿层（205）并且厚度大于所述串联谐振器的温度补偿层（205）。上述技术方案，兼顾了压电滤波器（100）的左侧滚降，以及通带插入损耗性能的较优选择。

Description

压电滤波器及其质量负载实现方法和含压电滤波器的装置 技术领域
本发明涉及微电子技术领域，涉及压电滤波器及其质量负载实现方法和含压电滤波器装置，特别地涉及一种实现压电滤波器质量负载的方法、压电滤波器、双工器、高频前端电路以及通信装置。
背景技术
目前，能够满足通讯终端使用的小尺寸滤波类器件主要是压电声波滤波器，构成此类声波滤波器的谐振器主要包括：FBAR(Film Bulk Acoustic Resonator，薄膜体声波谐振器)，SMR(Solidly Mounted Resonator，固态装配谐振器)和SAW(Surface Acoustic Wave，表面声波谐振器)。其中基于体声波原理FBAR和SMR制造的滤波器(统称为BAW，体声波谐振器)，相比基于表面声波原理SAW制造的滤波器，具有更低的插入损耗，更快的滚降特性等优势。
由于构成声波谐振器的压电材料和金属材料，都具有负温度系数的特点，即当温度增加时，谐振器的谐振频率均会以一定比例向低频方向移动(温度漂移)。一般情况下，SAW的温度系数为-35ppm/℃～-50ppm/℃,BAW的温度系数为-25ppm/℃～-30ppm/℃。虽然BAW相比SAW具有明显的温度漂移方面的性能优势，但是在一些特殊的应用场景下，这样的温度系数，仍然会对应用了滤波器的射频收发系统的性能产生不利影响，例如一个滤波器定义了从通带边缘到带外抑制的频率可变范围，那么温度系数的存在，就使得在考虑了温度漂移频率之后，这个可变范围变小，从而大大增加了滤波器的设计难度。
为了解决滤波器普遍存在的温度漂移问题，一个常见的解决方法是，在谐振器中加入可以实现温度补偿效果的材料。对于声波谐振器，这种温度补偿材料常常被选择为二氧化硅，主要是因为二氧化硅具有与大多数材料正好相反的正温度系数，并且可以通过一般的工艺制程 制作，也同时具备低廉的价格，适合产品大批量生产的应用。这类加了温度补偿的材料的谐振器，也被称为TCF谐振器，是温度补偿滤波器的组成单元。
但是，在谐振器引入温度补偿层不是没有代价的，它使谐振器的特性变差，主要体现在谐振器损耗的增大，以及机电耦合系数的变小。谐振器的损耗增大，滤波器的插入损耗会随之增加，从而增大射频链路中的损耗，恶化射频前端的收发性能。机电耦合系数变小，谐振器的串联谐振频率和并联谐振频率之间的间距减小，滤波器的滚降特性有可能改善，但同时滤波器的带宽也会变窄，大多数通信系统中，滤波器的带宽是根据系统要求提出的，带宽并不能无限制的缩窄。
因此，如何在有一定带宽要求的情况下，实现BAW滤波器件的高滚降要求和温度特性，成为滤波器设计工程师一个亟待解决的问题。
发明内容
有鉴于此，本发明提供一种实现压电滤波器质量负载的方法、压电滤波器、双工器、高频前端电路以及通信装置，以解决现有技术中的技术问题。
为实现上述目的，根据本发明的一个方面，提供了一种实现压电滤波器的质量负载的方法。
本发明的实现压电滤波器的质量负载的方法中，所述压电滤波器包括串联支路和并联支路，所述串联支路包括三个以上串联在所述压电滤波器的输入输出端之间的体声波谐振器，相邻谐振器的连接点与接地端之间设置有并联电路，在该方法中，将谐振器的温度补偿层作为质量负载，并且：所有串联谐振器均为相同的谐振器，各串联谐振器具有或不具有温度补偿层；所有并联谐振器均具有温度补偿层并且厚度大于所述串联谐振器的温度补偿层。
本发明中，如只在并联谐振器上添加温补层的滤波器，相比没有温补层的普通压电滤波器，具有以下优点：并联谐振器采用零温漂、 小Kt 2的温补谐振器，可以有效改善滤波器左侧的滚降特性。同时，它相比串、并联谐振器全部采用温补谐振器制作的温补滤波器具有以下优点：1)采用温补层作为质量负载，省去了另外制作质量负载的工艺步骤；2)串联谐振器采用普通谐振器而非温补谐振器，谐振器损耗相对较好，从而改善了滤波器的插入损耗特性；3)串联谐振器采用普通谐振器而非温补谐振器，适当减少了温补谐振器Kt 2变小对滤波器带宽的缩减作用。
可选地，所述并联谐振器的温度补偿层的厚度满足如下条件：该温度补偿层产生的正温漂效应对所述并联谐振器的其他层的负温漂效应的抵消作用，使所述并联谐振器的温度系数在0ppm/℃的指定范围的邻域内。
可选地，所述并联谐振器的温度补偿层的厚度进一步满足如下条件：所述并联谐振器的温度补偿层的厚度产生的质量负载效应，使得串联谐振器的串联谐振频率与添加温度补偿层之后的并联谐振器的并联谐振频率的差值在预设范围内。
可选地，还包括：调整所述并联谐振器的上电极、下电极、压电层、以及温度补偿层中的一个或多个的厚度，使所述并联谐振器的温度系数在0ppm/℃的预设范围的邻域内，并且调整所述串联谐振器的上电极、下电极、压电层、以及温度补偿层中的一个或多个的厚度，使所述串联谐振器的温度系数在一个小于0ppm/℃的指定值的预设范围的邻域内，以调整所述滤波器的滚降性能。
根据本发明的另一方面，提供了一种压电滤波器。
本发明的压电滤波器包括串联支路和并联支路，所述串联支路包括三个以上串联在所述压电滤波器的输入输出端之间的体声波谐振器，相邻谐振器的连接点与接地端之间设置有并联电路，所有串联谐振器均为相同的谐振器，各串联谐振器具有或不具有温度补偿层；所有并 联谐振器均具有温度补偿层并且厚度大于所述串联谐振器的温度补偿层。
可选地，所述并联谐振器的温度补偿层的厚度满足如下条件：该温度补偿层产生的正温漂效应对所述并联谐振器的其他层的负温漂效应的抵消作用，使所述并联谐振器的温度系数在0ppm/℃的指定范围的邻域内。
可选地，所述并联谐振器的温度补偿层的厚度进一步满足如下条件：所述并联谐振器的温度补偿层的厚度产生的质量负载效应，使得串联谐振器的串联谐振频率与添加温度补偿层之后的并联谐振器的并联谐振频率的差值在预设范围内。
根据本发明的又一方面，提供了一种双工器，包括本发明所述的压电滤波器。
根据本发明的又一方面，一种高频前端电路，包括本发明所述的压电滤波器。
根据本发明的又一方面，提供了一种通信装置，包括本发明所述的压电滤波器。
附图说明
附图用于更好地理解本发明，不构成对本发明的不当限定。其中：
图1A是BAW的电学符号，图1B是BAW的等效电学模型图；
图2是谐振器阻抗与fs、fp的关系示意图；
图3是传统普通谐振器示意图；
图4是温补谐振器示意图；
图5是加温度补偿层前和加温度补偿层后谐振器的性能对比示意图；
图6是本发明实施例的压电滤波器100的电路图；
图7是第一对比例压电滤波器001的电路图；
图8A是压电滤波器001的串并联谐振器阻抗-频率关系示意图，图8B是压电滤波器100的串并联谐振器阻抗-频率关系示意图；
图9A是压电滤波器100与压电滤波器001的幅频曲线对比示意图，图9B是图9A的局部放大图；
图10A是压电滤波器001在低温、常温、高温下的三温曲线示意图，图10B是图10A的局部放大图；
图11A是压电滤波器100在低温、常温、高温下的三温曲线示意图，图11B是图11A的局部放大图；
图12是第二对比例压电滤波器002的电路图；
图13A是压电滤波器002的串并联谐振器阻抗-频率关系示意图，图13B是压电滤波器100的串并联谐振器阻抗-频率关系示意图；
图14A是压电滤波器100与压电滤波器002的幅频曲线对比示意图，图14B是图14A的局部放大图；
图15是根据本发明实施方式的一种滤波器的结构的示意图，其中串联滤波器和并联滤波器都具有温补层。
具体实施方式
下面详细描述本发明的实施例，所述实施例的示例在附图中示出，其中自始至终相同或类似的标号表示相同或类似的元件或具有相同或类似功能的元件。下面通过参考附图描述的实施例是示例性的，旨在用于解释本发明，而不能理解为对本发明的限制。
为使本领域技术人员更好地了解本发明的内容，发明人先对温补谐振器的基础结构和性能做简要介绍。
图1A是压电声波谐振器的电学符号，图1B是其等效电学模型图，在不考虑损耗项的情况下，电学模型简化为L m、C m和C 0组成的谐振电路。根据谐振条件可知，该谐振电路存在两个谐振频点：一个是谐振电路阻抗值达到最小值时的f s，将f s定义为该谐振器的串联谐振频点；另一个是当谐振电路阻抗值达到最大值时的f p，将f p定义为该谐振器 的并联谐振频点。其中，
Figure PCTCN2020141269-appb-000001
并且，f s比f p要小。同时，定义了谐振器的机电耦合系数Kt 2 eff(以下简记为Kt 2)，它可以用f s和f p来表示：
Figure PCTCN2020141269-appb-000002
图2示出了谐振器阻抗与f s和f p之间的关系。在某一特定的频率下，有效机电耦合系数越大，则f s和f p的频率差越大，即两个谐振频点离得越远。同时，将谐振器在f s处的阻抗幅值定义为R s，它是谐振器阻抗曲线中的极小值；将谐振器在f p处的阻抗幅值定义为R p，它是谐振器阻抗曲线中的极大值。R s和R p是描述谐振损耗特性的重要参数，当R s越小，R p越大时，谐振器的损耗越小，Q值越高，此时滤波器的插入损耗特性也更好。
图3是传统普通谐振器示意图。如图3所示，谐振器制作在衬底104之上，底电极102和顶电极101为金属电极，厚度通常为几百纳米。压电材料薄膜103通常使用氧化锌或氮化铝材料，厚度为几百纳米至几微米。为了使得在其中产生的声波能够实现谐振，需要使得声波在顶底电极表面产生反射。顶电极101之上是能够形成声波反射的空气，为了使得声波在底电极下表面也产生反射，在底电极102下制作有空气腔100。当交变电压施加在顶电极101和底电极102上时，激发压电材料薄膜103产生压电效应产生机械声波。声波在顶底电极之间传播并反射，形成驻波谐振，进而在电学响应上形成谐振。由于使用空腔形成反射，这种谐振器称作空腔反射式体声波谐振器。
图4是温补谐振器示意图。该温补谐振器可以包括：顶电极201、底电极202、压电层203、衬底204、位于底电极202内部的温度补偿层205以及空气腔200，可以视为是在图3的基础上添加了温度补偿层的FBAR谐振器。温度补偿层205的材料一般为二氧化硅，并且其图形小于或等于底电极图形，也就是说补偿层和底电极看起来仿佛夹心 饼干或者三明治。优选地，温度补偿层205被完全包裹于底电极材料中，这样制作的好处是，可以有效的保护它不受其它工艺制作过程的破坏。另外，因为温度补偿层上面和下面的电极材料在边缘处连接在一起，避免了形成由三者组成的寄生电容，从而大幅度恶化谐振器的Kt 2和损耗特性。可选地，温度补偿层的版图面积与底电极顶层或底电极底层的版图面积之比为0.5～1。
图5A和图5B是谐振器中加温度补偿层前后的谐振器阻抗曲线对比。添加了温度补偿层后，谐振器的Kt 2由原来的6.5％减少为3.4％，R s由原来的0.66欧姆增大到1.37欧姆，而Rp则由原来的2592欧姆减小到1314欧姆，同时谐振器的温度系数由原来的-25ppm/℃～-30ppm/℃变为约0ppm/℃左右。可以看到，添加了温度补偿层，Kt 2会变为原来的大约一半，R s会增大到大约原来的2倍，而R p则减少到原来的大约一半，谐振器的损耗增加也一定程度上导致了Q值的降低。
本发明第一方面提出一种实现压电滤波器的质量负载的方法，压电滤波器包括串联支路和并联支路，串联支路包括三个以上串联在压电滤波器的输出输出端之间的体声波谐振器，相邻谐振器的连接点与接地端之间设置有并联电路，在该方法中，将谐振器的温度补偿层作为质量负载，并且：所有串联谐振器均为相同的谐振器，各串联谐振器具有或不具有温度补偿层；所有并联谐振器均具有温度补偿层并且厚度大于串联谐振器的温度补偿层。
需要说明的是，串联谐振器为相同的普通谐振器的情形，具有结构简单，易于加工的优点。该实施例中，串联谐振器中的温度补偿层厚度为零，因此串并联谐振器的温度补偿层厚度差等于并联谐振器中的温度补偿层厚度。还需要说明的是，串联谐振器为相同的温补谐振器，并且串联谐振器的温度补偿层厚度小于并联谐振器的温度补偿层厚度的情形，串联谐振器存在温度补偿层厚度差异，以保证实现串并联频率差，也就是实现负载效应。
进一步地，串联谐振器的温度系数为零。这意味着温度补偿层产生的正温漂效应可以正好抵消所有其它层的负温漂效应，从而使得并 联谐振器成为具有温度系数等于0ppm/℃的温补谐振器。该实施例中，温度系数为零意味着温度补偿层的温漂效应与其他层的温漂效应恰好抵消，这样压电滤波器在不同环境温度下具有稳定的电学性能。
进一步地，并联谐振器的温度补偿层的厚度等同于质量负载效应，使得添加温度补偿层之后的并联谐振器的并联谐振频率与串联谐振器的串联谐振频率相等。意味着温度补偿层的厚度正好等同于质量负载效应，使得添加温度补偿层之后的并联谐振器的并联谐振频率，与未添加温度补偿层的串联谐振器的串联谐振频率差不多相等，从而形成滤波器的特性曲线。
本发明实施例的实现压电滤波器的质量负载的方法，无论是相比串并联谐振器全部设置普通FBAR谐振器的情形，还是相比串并联谐振器全部设置为温补谐振器的情形，均在性能上具有明显优势，兼顾了左侧滚降，以及通带插入损耗性能的较优选择。
本发明第二方面提出一种压电滤波器，包括串联支路和并联支路，串联支路包括三个以上串联在压电滤波器的输出端之间的体声波谐振器，相邻谐振器的连接点与接地端之间设置有并联电路，其特征在于，所有串联谐振器均为相同的谐振器，各串联谐振器具有或不具有温度补偿层；所有并联谐振器均具有温度补偿层并且厚度大于串联谐振器的温度补偿层。
进一步地，串联谐振器的温度系数为零。
进一步地，并联谐振器的温度补偿层的厚度等同于质量负载效应，使得添加温度补偿层之后的并联谐振器的并联谐振频率与串联谐振器的串联谐振频率相等。
本发明实施例的压电滤波器，无论是相比全部为普通FBAR谐振器的滤波器，还是全部为温补谐振器的滤波器，均在性能上具有明显优势，兼顾了左侧滚降，以及通带插入损耗性能的较优选择。
下面列举本发明实施例的压电滤波器与两种其他的压电滤波器做性能对比。
本发明实施例的压电滤波器100，其电路图如图6所示，包括5个串联谐振器和4个并联谐振器。其中所有并联谐振器均为如图4的温补谐振器，所有串联谐振器均为如图3的普通FBAR谐振器。该滤波器的通带频率范围为2565MHz～2595MHz，通带带宽为30MHz，并且要求在2540MHz处有大于45dB的带外抑制。
提供第一对比例——压电滤波器001，其电路图如图7所示，包括5个串联普通谐振器和4个并联普通谐振器。该压电滤波器001由串联谐振器与并联谐振器组成类似于梯型的级联结构，并在其中并联谐振器上添加质量负载层，材料与制作BAW器件的电极材料相同，使其并联谐振频率与串联谐振器的谐振频率基本相同，从而形成滤波器的曲线特性。
图8A是压电滤波器001的串并联谐振器阻抗-频率关系示意图，图8B是压电滤波器100的串并联谐振器阻抗-频率关系示意图。两图对比可知，滤波器要求在2540MHz处有大于45dB的带外抑制，实施例压电滤波器100和第一对比例压电滤波器001中的并联谐振器的串联谐振频率，均设置在2530MHz附近，但由于实施例中的并联谐振器为Kt2相对较小的温补谐振器，其fs与fp之间的距离更小，因此实施例中的串联谐振器的串联谐振频率相比第一对比例会明显偏低，这是为了保证滤波器在通带范围内的阻抗匹配特性。
图9A是压电滤波器100(实线)与压电滤波器001(虚线)的幅频曲线对比示意图，图9B是图9A的局部放大图。由于压电滤波器001采用的均是普通FBAR谐振器，其Kt2约为6.5％，滤波器的带宽较宽。为保证2540MHz处的带外抑制，滤波器在2565MHz的插入损耗约为3.2dB，同时因为通带较宽，通带右侧的插入损耗可以达到将近1.0dB，30MHz通带范围内的波动值较大。而实施例的并联谐振器采用温补谐振器，其Kt2约为3.4％，从阻抗极小值到阻抗极大值过渡的频率范围会更小，因此可以实现更好的左侧滚降特性。同时，并联谐振器的零温漂特性，也使得滤波器左侧滚降沿随着温度的变化改变很小，这进一步增加了滤波器滚降的余量。
图10A是压电滤波器001在低温、常温、高温下的三温曲线示意 图，图10B是图10A的局部放大图。其中黑色实线为常温下的曲线，因为所采用的所有谐振器具有-25ppm/℃～-30ppm/℃的温度系数，因此与常温曲线相比，滤波器在低温下幅频曲线向高频方向移动，同时插入损耗变好，而高温下幅频曲线向低频方向移动，同时插入损耗变差。
图11A是压电滤波器100在低温、常温、高温下的三温曲线示意图，图11B是图11A的局部放大图。其中黑色实线为常温下的曲线，因为串联谐振器为普通谐振器，具有-25ppm/℃～-30ppm/℃的温度系数，而并联谐振器为温补谐振器，具有0ppm/℃的温度系数，因此与常温曲线相比，滤波器在低温下幅频曲线的右边沿向高频方向移动，同时插入损耗变好，而高温下幅频曲线的右边沿向低频方向移动，同时插入损耗变差。滤波器的右边沿被温补谐振器的零温漂特性锚定，从面频率位置改变很小，从而改善了满眼波器相应位置的滚降特性。
由上文的压电滤波器100与压电滤波器001的对比可知，只在并联谐振器上添加温度补偿层的滤波器，相比没有温度补偿层的普通压电滤波器，具有以下优点：并联谐振器采用零温漂、小Kt 2的温补谐振器，可以有效改善滤波器左侧的滚降特性。
提供第二对比例——压电滤波器002，其电路图如图12所示，包括5个串联温补谐振器和4个并联温补谐振器。
图13A是压电滤波器002的串并联谐振器阻抗-频率关系示意图，图13B是压电滤波器100的串并联谐振器阻抗-频率关系示意图，可以看出压电滤波器002具有Kt 2小，损耗大，零温漂的特点。
图14A是压电滤波器100(实线)与压电滤波器002(虚线)的幅频曲线对比，图14B是图14A的局部放大图。由于压电滤波器002采用的均是温补谐振器，其Kt 2约为3.4％，并且损耗较大，因此滤波器的带宽较窄，在2565MHz的插入损耗约为3.6dB，在2595MHz的插入损耗约为2.6dB，通带内的总体带内插入损耗相比实施例，差了约0.35dB。虽然压电滤波器002因为全部采用温补谐振器，其左右两侧滚降沿的温度漂移特性均较好，但是其带宽和插入损耗方面的损失较大，不能满足滤波器的应用需求。
由上文的压电滤波器100与压电滤波器002的对比可知，相比串、 并联谐振器全部采用温补谐振器制作的压电滤波器，本发明实施例的压电滤波器具有以下优点：(1)采用温度补偿层作为质量负载，省去了另外制作质量负载的工艺步骤；(2)串联谐振器采用普通谐振器而非温补谐振器，谐振器损耗相对较好，从而改善了滤波器的插入损耗特性；(3)串联谐振器采用普通谐振器而非温补谐振器，适当减少了温补谐振器Kt 2变小对滤波器带宽的缩减作用。
图15是根据本发明实施方式的一种滤波器的结构的示意图。如图15中所示的FBAR滤波器300，其电路图与图11相同，串联和并联均为温补谐振器。图中示出了做在衬底上的空腔，下电极，压电层，上电极，以及被包裹在下电极，位于谐振区内的温补层。需要说明的是，为了保护谐振器不受环境影响而发生氧化，通常在上电极上方，还会制作一层钝化层，它的材料可以是性能相对稳定的非金属材料，如二氧化硅，甚至也可以与压电层采用相同的材料，如氮化铝。图15中左侧的谐振器为串联谐振器，右侧的谐振器为并联谐振器，其它滤波器中的谐振器并未示出。串联谐振器的温补层厚度为t1，并联谐振器的温补层厚度为t2，t1和t2满足关系，t2>t1，二者的厚度差，即形成了并联谐振器与串联谐振的频差，即滤波器设计所需要的质量负载效应。串联谐振器与并联谐振器的其它层厚度均相同，为了更好的表现出各层厚度关系，此图相比前面谐振器，更详细的表现出了各层因为温补层厚度不同，在薄膜沉积制作过程中形成的边界斜角。在此实施例中，由于串联和并联谐振器的温补层厚度不同，而其它层相同，因此两种谐振器的温度系数必定不同。在设计过程中，可以根据滤波器电性能的特点，选择合适的层叠，使得相应位置的温度系数更接近于0ppm/℃。例如：对于滤波器通带左侧有滚降要求的，可以设计各层厚度，使得并联谐振器的温度系数为0ppm/℃左右，而串联谐振器的温度系数可以相比0ppm/℃相差远一些，如-10ppm。这样形成的滤波器，可以得到更好的左侧滚降，同时右侧滚降相比没有温补谐振器的滤波器，也会有一定的提升。
综上，本发明实施例的压电滤波器，无论是相比全部为普通FBAR谐振器的滤波器，还是全部为温补谐振器的滤波器，均在性能上具有 明显优势，兼顾了左侧滚降，以及通带插入损耗性能的较优选择。
上述具体实施方式，并不构成对本发明保护范围的限制。本领域技术人员应该明白的是，取决于设计要求和其他因素，可以发生各种各样的修改、组合、子组合和替代。任何在本发明的精神和原则之内所作的修改、等同替换和改进等，均应包含在本发明保护范围之内。

Claims (10)

  1. 一种实现压电滤波器的质量负载的方法，所述压电滤波器包括串联支路和并联支路，所述串联支路包括三个以上串联在所述压电滤波器的输入输出端之间的体声波谐振器，相邻谐振器的连接点与接地端之间设置有并联电路，其特征在于，在该方法中，将谐振器的温度补偿层作为质量负载，并且：
    所有串联谐振器均为相同的谐振器，各串联谐振器具有或不具有温度补偿层；
    所有并联谐振器均具有温度补偿层并且厚度大于所述串联谐振器的温度补偿层。
  2. 根据权利要求1所述的方法，其特征在于，所述并联谐振器的温度补偿层的厚度满足如下条件：该温度补偿层产生的正温漂效应对所述并联谐振器的其他层的负温漂效应的抵消作用，使所述并联谐振器的温度系数在0ppm/℃的指定范围的邻域内。
  3. 根据权利要求2所述的方法，其特征在于，所述并联谐振器的温度补偿层的厚度进一步满足如下条件：所述并联谐振器的温度补偿层的厚度产生的质量负载效应，使得串联谐振器的串联谐振频率与添加温度补偿层之后的并联谐振器的并联谐振频率的差值在预设范围内。
  4. 根据权利要求1所述的方法，其特征在于，还包括：
    调整所述并联谐振器的上电极、下电极、压电层、以及温度补偿层中的一个或多个的厚度，使所述并联谐振器的温度系数在0ppm/℃的预设范围的邻域内，并且调整所述串联谐振器的上电极、下电极、压电层、以及温度补偿层中的一个或多个的厚度，使所述串联谐振器的温度系数在一个小于0ppm/℃的指定值的预设范围的邻域内，以调整所述滤波器的滚降性能。
  5. 一种压电滤波器，包括串联支路和并联支路，所述串联支路包括三个以上串联在所述压电滤波器的输入输出端之间的体声波谐振器，相邻谐振器的连接点与接地端之间设置有并联电路，其特征在于，
    所有串联谐振器均为相同的谐振器，各串联谐振器具有或不具有温度补偿层；
    所有并联谐振器均具有温度补偿层并且厚度大于所述串联谐振器的温度补偿层。
  6. 根据权利要求5所述的压电滤波器，其特征在于，所述并联谐振器的温度补偿层的厚度满足如下条件：该温度补偿层产生的正温漂效应对所述并联谐振器的其他层的负温漂效应的抵消作用，使所述并联谐振器的温度系数在0ppm/℃的指定范围的邻域内。
  7. 根据权利要求6所述的压电滤波器，其特征在于，所述并联谐振器的温度补偿层的厚度进一步满足如下条件：所述并联谐振器的温度补偿层的厚度产生的质量负载效应，使得串联谐振器的串联谐振频率与添加温度补偿层之后的并联谐振器的并联谐振频率的差值在预设范围内。
  8. 一种双工器，其特征在于，包括权利要求5至7中任一项所述的压电滤波器。
  9. 一种高频前端电路，其特征在于，包括权利要求5至7中任一项所述的压电滤波器。
  10. 一种通信装置，其特征在于，包括权利要求5至7中任一项所述的压电滤波器。
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