CN-115459730-B - Bulk acoustic wave resonator, filter, duplexer and multiplexer design method

CN115459730BCN 115459730 BCN115459730 BCN 115459730BCN-115459730-B

Abstract

The invention provides a design method of a bulk acoustic wave resonator, a filter, a duplexer and a multiplexer, which comprises the following steps: an original Mason model is constructed, and a new model capable of precisely mapping the longitudinal wave sound velocity and the material density of the piezoelectric material and the parallel resonance is extracted according to the Mason model. And determining longitudinal wave sound velocity parameters and material density parameters for design by using a new model. The design method simplifies redundant parameters, eliminates irrelevant parameters, carries out limited setting on relatively fixed parameters, and establishes a mapping corresponding model of the limited parameters, thereby being capable of more accurately determining material parameters, such as longitudinal wave sound velocity parameters and material density parameters, compared with the prior art model. On the other hand, the invention also provides a design method of the doped bulk acoustic wave resonator, compared with the existing doping design method, the doping design method can obtain the design parameters of the resonator with the target frequency more stably, the design period is greatly reduced, and the design cost is greatly reduced.

Inventors

LAI ZHIGUO
YANG QINGHUA

Assignees

苏州汉天下电子有限公司
苏州汉天下电子有限公司

Dates

Publication Date: 20260421
Application Date: 20220902
Priority Date: 20220902

Claims (10)

1. A method of designing a bulk acoustic wave resonator, wherein the method of designing comprises: Step S101, constructing a Mason model of a bulk acoustic wave resonator; The bulk acoustic wave resonator comprises a laminated structure, wherein the laminated structure at least comprises a top electrode, a piezoelectric layer and a bottom electrode; step S102, respectively adjusting parameters in a Mason model to check the change condition of the frequency of the resonator; Step S103, discarding parameters irrelevant to the resonance frequency, converting the impedance expression of the bulk acoustic wave resonator into an impedance expression of an ideal bulk acoustic wave resonator only with a piezoelectric layer, and establishing a corresponding relation between the parallel resonance frequency and the longitudinal wave sound velocity of the piezoelectric layer and the material density of the piezoelectric layer to form a new equivalent model; Step S104, verifying engineering flow sheets, and fitting and adjusting longitudinal wave sound velocity and material density parameters in a new equivalent model; Step S105, bringing the sound velocity of the longitudinal wave and the material density after fitting and trimming into an initial Mason model, and fitting and trimming other design parameters according to the resonator parameters actually measured after engineering flow sheet in the step S104; and S106, after fitting and trimming, obtaining the design parameters of the final bulk acoustic wave resonator, and designing the resonator, the filter, the duplexer or the multiplexer by utilizing the parameters.
2. The method according to claim 1, wherein: The Mason model comprises an acoustic equivalent model and an electrical equivalent circuit; The acoustic equivalent model at least comprises a cascaded top electrode equivalent circuit, a piezoelectric layer equivalent circuit and a bottom electrode equivalent circuit; the electrical equivalent circuit comprises a static capacitor, a loss resistor and an electrical port; The acoustic equivalent model and the electrical equivalent circuit are coupled through a floating ground and an ideal transformer.
3. The method of claim 1, wherein the parameters adjusted in step S102 include thickness of each stacked structure of the resonator, static capacitance C 0 , loss resistance R S , loss resistance R 0 , loss resistance R m , longitudinal wave sound velocity, and material density.
4. The method of claim 1, wherein the other design parameters in step S105 include a static capacitance C 0 , a loss resistance R S , a loss resistance R 0 , a loss resistance R m , and an effective electromechanical coupling coefficient kt 2 .
5. The method of claim 1, wherein the parallel resonant frequency is: Wherein m=0, 1, 2, 3.,. D AlN is the thickness of the piezoelectric layer, and V AlN is the longitudinal wave sound velocity of the piezoelectric layer.
6. The method of claim 1, wherein the piezoelectric layer is an undoped piezoelectric layer.
7. The method according to any one of claims 1-5, further comprising the step of: Step S201, a resonator meeting the design frequency requirement is screened out from the previous engineering wafer, and the measured data of the resonator in the wafer flowing process is extracted; Step S202, calculating the sound velocity of the doped longitudinal wave and the density value of the material, and taking the sound velocity and the density value of the material into an initial Mason model to obtain a theoretical frequency offset; Step S203, adjusting the thickness of the lamination to make the frequency offset equal to the theoretical frequency offset in the step, and the offset directions are opposite, thereby obtaining the thickness of the lamination of the doped resonator; Step S204, the parameters obtained in the step S203 are brought into an initial Mason model to set a doped bulk acoustic wave resonator, a filter or a duplexer, an engineering flow sheet is doped, and doping design parameters are adjusted according to the actual measurement parameters of the doped resonator after the engineering flow sheet is doped; in step S205, the doping design parameters of the finally doped bulk acoustic wave resonator are obtained, and the doped bulk acoustic wave resonator, the filter, the duplexer or the multiplexer are designed according to the doping design parameters.
8. The method of claim 7, wherein the values of the longitudinal wave sound velocity and the material density after doping are calculated by substituting the atomic mass ratio of the material for the material density ratio to calculate the longitudinal wave sound velocity relationship and the material density relationship of the doped material and the undoped material.
9. The method of claim 7, wherein the fitting of the trimmed doping design parameters in step S204 includes resonator stack thickness, static capacitance C 0 , loss resistance R S , loss resistance R 0 , loss resistance R m .
10. The method of claim 7, wherein the doping design parameters of step S205 include longitudinal wave acoustic velocity, material density, static capacitance C 0 , loss resistance R S , loss resistance R 0 , loss resistance R m , effective electromechanical coupling coefficient kt 2 .

Description

Bulk acoustic wave resonator, filter, duplexer and multiplexer design method Technical Field The present invention relates to the field of bulk acoustic wave resonators, and in particular, to a bulk acoustic wave resonator, a filter, a duplexer, and a method for designing a multiplexer. Background The core component of the bulk acoustic wave filter is a bulk acoustic wave resonator, and the bulk acoustic wave filter may also constitute a duplexer or a multiplexer. The bulk acoustic wave resonator comprises a laminated structure, wherein the laminated structure comprises a top electrode, a piezoelectric layer and a bottom electrode from top to bottom in sequence. The bulk acoustic wave resonator has the characteristics of small volume, small insertion loss and the like, so that the bulk acoustic wave resonator becomes one of the most widely applied filters in the current mobile communication field. The design parameters can be finally determined after more than one engineering flow sheet is generally experienced in the design process of the bulk acoustic wave resonator, and the product is designed according to the finally determined design parameters, wherein the existing design flow is to design by adopting a Mason model or an MBVD model firstly, then fit and adjust the parameters of the Mason model or the MBVD model according to the actual measurement result of the engineering flow sheet, and when the model value and the actual measurement value meet a certain error range, the final product design parameters are obtained. However, in the above design flow, since the model parameters are numerous, the parameters are often not easy to be adjusted, in addition, the advantages of model establishment and the determination of the parameter values directly affect the design accuracy, and the center frequency of the bulk acoustic wave filter after the first flow sheet is often a frequency difference of tens to hundreds of megahertz compared with the design value, because the use of bulk acoustic wave resonator material parameters is involved in the design process of the bulk acoustic wave filter, wherein the material parameters of the bulk acoustic wave resonator refer to the longitudinal wave sound velocity and the material density of each layer in the laminated structure. Since the design value of the bulk acoustic wave resonator material parameter is often a reference value, and there is a deviation between the actual value of the bulk acoustic wave resonator material parameter after the flow sheet, there is also a certain deviation between the center frequency of the bulk acoustic wave filter formed by the flow sheet and the design value thereof. The magnitude of the deviation directly affects the difficulty and period of the later design, and even multiple stream verification may be required. Based on this, there is an urgent need in the art for a method of designing a bulk acoustic wave resonator that can reduce design deviation, save design costs, and shorten design cycle time. In addition, with the popularity of doping process, how to design the doping process flow based on the existing non-doping process is also an urgent problem in the field to be solved. Disclosure of Invention In order to overcome the above-mentioned drawbacks in the prior art, the present invention provides a method for designing a bulk acoustic wave resonator, a filter, a duplexer, and a multiplexer, the method comprising: Step S101, constructing a Mason model of a bulk acoustic wave resonator, wherein the bulk acoustic wave resonator comprises a laminated structure at least comprising a top electrode, a piezoelectric layer and a bottom electrode; step S102, respectively adjusting parameters in a Mason model to check the change condition of the frequency of the resonator; The parameters to be adjusted include, but are not limited to, thickness of each laminated structure of the resonator, static capacitance C 0, loss resistance R S、R0、Rm, longitudinal wave sound velocity, material density and the like; Step S103, discarding parameters irrelevant to the resonance frequency, and establishing a corresponding relation between the parallel resonance frequency and the longitudinal wave sound velocity and material density to form a new equivalent model; The acoustic equivalent part of the new equivalent model is completely the same as the initial Mason model, so that the material parameters in the new model, such as longitudinal wave sound velocity and material density, can be completely applied to the initial Mason model without affecting the accuracy of the model. Step S104, designing with a new equivalent model, verifying engineering flow sheets, and fitting and adjusting longitudinal wave sound velocity and material density parameters in the new equivalent model; Step S105, bringing the sound velocity of the longitudinal wave and the material density after fitting and trimming into an initial Mason model, and fitting and trimming other