Separation step acoustic wave filter

Abstract

A filter device and a method of manufacturing a filter device. The filter device includes a first chip and a second chip. The first chip has a first material stack and contains one or more series resonators of a step filter circuit. The second chip has a second material stack and contains one or more parallel resonators of the step filter circuit. The first material stack and the second material stack are different.

Description

[0001] This application is a divisional application of the Chinese invention patent application "Separated Step Acoustic Wave Filter" with an application date of June 17, 2020 and application number 202080044128.1. Technical Field

[0002] The present disclosure relates to radio frequency filters using acoustic wave resonators, and more particularly to filters for use in communication devices. Background Art

[0003] Radio frequency (RF) filters are two-terminal devices that are configured to pass some frequencies and block other frequencies, where "pass" means transmission with relatively low insertion loss, and "block" means blocking or substantially attenuating. The range of frequencies passed by a filter is called the "passband" of the filter. The range of frequencies blocked by such a filter is called the "stopband" of the filter. Typical RF filters have at least one passband and at least one stopband. The specific requirements of the passband or stopband depend on the specific application. For example, a "passband" can be defined as a frequency range where the insertion loss of the filter is less than a defined value such as 1dB, 2dB, or 3dB. A "stopband" can be defined as a frequency range where the insertion loss of the filter is greater than a defined value, such as 20dB, 30dB, 40dB, or more, depending on the specific application.

[0004] RF filters are used in communication systems that transmit information over wireless links. For example, RF filters can be found in the RF front end of base stations, mobile phones and computing devices, satellite transceivers and ground stations, Internet of Things (IoT) devices, laptops and tablets, fixed-point radio links, and other communication systems. RF filters are also used in radars and electronic and information warfare systems.

[0005] RF filters typically require many design trade-offs to achieve the best compromise between performance parameters such as insertion loss, rejection, isolation, power handling, linearity, size, and cost for each specific application. Specific design and manufacturing methods and enhancements can benefit one or several of these requirements simultaneously.

[0006] Enhancements in the performance of RF filters in wireless systems can have a wide range of impacts on system performance. Improvements in RF filters can lead to improvements in system performance, such as larger unit size, longer battery life, higher data rates, greater network capacity, lower cost, enhanced security, higher reliability, etc. These improvements can be achieved individually or in combination at various levels of the wireless system, such as at the RF module, RF transceiver, mobile or fixed subsystem, or network level. Summary of the invention

[0007] The present invention discloses a filter device, comprising: a first chip having a first material stack, the first chip containing one or more series resonators of a ladder filter circuit; and a second chip having a second material stack, the second chip containing one or more parallel resonators of the ladder filter circuit, wherein the first material stack and the second material stack are different.

[0008] The first chip includes all series resonators of the ladder filter circuit, and the second chip includes all parallel resonators of the ladder filter circuit.

[0009] The first chip and the second chip are attached to a circuit card, the circuit card comprising at least one conductor for electrically connecting between one of the one or more series resonators and one of the one or more parallel resonators.

[0010] The first material stack includes a first piezoelectric element, the second material stack includes a second piezoelectric element, and the first piezoelectric element and the second piezoelectric element are different in at least one of material, thickness, and orientation of a crystal axis of the material.

[0011] The one or more series resonators and the one or more parallel resonators are non-coupled SAW (surface acoustic wave) resonators, and the first material stack and the second material stack have differences in one or more of the following aspects: the material of the piezoelectric plate, the thickness of the piezoelectric plate, the orientation of the crystal axis of the piezoelectric plate, the material of the conductor pattern formed above the piezoelectric plate, the thickness of the conductor pattern, the material of the dielectric layer formed above the conductor pattern, and the thickness of the dielectric layer.

[0012] Wherein, the one or more series resonators and the one or more parallel resonators are combined chip resonators, and the first material stack and the second material stack have differences in one or more of the following aspects: the material of the base, the thickness of the base, the material of the dielectric layer between the base and the piezoelectric chip, the thickness of the dielectric layer between the base and the piezoelectric chip, the material of the piezoelectric chip, the thickness of the piezoelectric chip, the orientation of the crystal axis of the piezoelectric chip, the material of the conductor pattern formed above the piezoelectric chip, the thickness of the conductor pattern, the material of the dielectric layer formed above the conductor pattern, and the thickness of the dielectric layer formed above the conductor pattern.

[0013] The one or more series resonators and the one or more parallel resonators are floating diaphragm resonators, and the first material stack and the second material stack have differences in one or more of the following aspects: the material of the base, the thickness of the base, the material of the dielectric layer between the base and the piezoelectric wafer, the thickness of the dielectric layer between the base and the piezoelectric wafer, the material of the piezoelectric wafer, the thickness of the piezoelectric wafer, the orientation of the crystal axis of the piezoelectric wafer, the material of the conductor pattern formed above the piezoelectric wafer, the thickness of the conductor pattern, the material of the dielectric layer formed above the conductor pattern, and the thickness of the dielectric layer formed above the conductor pattern.

[0014] Among them, the one or more series resonators and the one or more parallel resonators are solid-state assembled diaphragm resonators, and the first material stack and the second material stack have differences in one or more of the following aspects: the material of the base, the thickness of the base, the number of layers of acoustic Bragg reflectors arranged between the base and the piezoelectric chip, and the material and thickness of each layer, the thickness of the dielectric layer between the base and the piezoelectric chip, the material of the piezoelectric chip, the thickness of the piezoelectric chip, the orientation of the crystal axis of the piezoelectric chip, the material of the conductor pattern formed above the piezoelectric chip, the thickness of the conductor pattern, the material of the dielectric layer formed above the conductor pattern, and the thickness of the dielectric layer formed above the conductor pattern.

[0015] The one or more series resonators and the one or more parallel resonators are thin film bulk acoustic wave resonators, and the first material stack and the second material stack have differences in one or more of the following aspects: the material of the base, the thickness of the base, the material of the lower conductor pattern, the lower conductor pattern is arranged between the base and the piezoelectric element, the thickness of the lower conductor pattern, the material of the piezoelectric element, the thickness of the piezoelectric element, the crystal axis orientation of the piezoelectric element, the material of the upper conductor pattern formed above the piezoelectric element, the thickness of the upper conductor pattern, the material of the dielectric layer formed above the upper conductor pattern, and the thickness of the dielectric layer.

[0016] The one or more series resonators and the one or more parallel resonators are solid-state assembled thin film bulk acoustic wave resonators, and the first material stack and the second material stack have differences in one or more of the following aspects: the material of the base, the thickness of the base, the number of layers of acoustic Bragg reflectors arranged between the base and the lower conductor pattern, and the material and thickness of each layer, the material of the lower conductor pattern arranged between the acoustic Bragg reflector and the piezoelectric element, the thickness of the lower conductor pattern, the material of the piezoelectric element, the thickness of the piezoelectric element, the crystal axis orientation of the piezoelectric element, the material of the upper conductor pattern formed above the piezoelectric element, the thickness of the upper conductor pattern, the material of the dielectric layer formed above the upper conductor pattern, and the thickness of the dielectric layer.

[0017] Wherein, the one or more series resonators and the one or more parallel resonators are combined chip resonators, the first material stack includes a 46-degree Y-cut lithium tantalate piezoelectric chip, and the second material stack includes a 42-degree Y-cut lithium tantalate piezoelectric chip.

[0018] Wherein, the one or more series resonators are bonded wafer resonators and the one or more parallel resonators are unbonded SAW resonators.

[0019] The present invention also discloses a duplexer, including a transmitting ladder filter circuit and a receiving ladder filter circuit, comprising: a first chip having a first material stack, the first chip containing one or more series resonators of the transmitting ladder filter circuit; and a second chip having a second material stack, the second chip containing one or more parallel resonators of the receiving filter circuit, wherein the first material stack and the second material stack are different.

[0020] Among them, the first chip includes a series resonator of the transmitting ladder filter circuit and the receiving ladder filter circuit, and the second chip includes a parallel resonator of the transmitting ladder filter circuit and the receiving ladder filter circuit.

[0021] The first chip includes all series resonators of the transmitting ladder filter circuit and the receiving ladder filter circuit, and the second chip includes all parallel resonators of the transmitting ladder filter circuit and the receiving ladder filter circuit.

[0022] The first chip includes the series resonator of the transmission ladder filter circuit, and the second chip includes the parallel resonator of the transmission ladder filter circuit and all the resonators of the reception filter circuit.

[0023] The series resonator of the transmission ladder filter circuit is a bonded chip resonator, and the parallel resonator of the transmission ladder filter circuit and all resonators of the reception filter circuit are non-bonded SAW resonators.

[0024] The present invention further discloses a method of producing a filter device, comprising: manufacturing a first chip having a first material stack, the first chip comprising one or more series resonators of a ladder filter circuit; and

[0025] A second chip having a second material stack is fabricated, the second chip including one or more parallel resonators of the ladder filter circuit, wherein the first material stack and the second material stack are different.

[0026] The first chip includes all series resonators of the ladder filter circuit, and the second chip includes all parallel resonators of the ladder filter circuit.

[0027] The first chip and the second chip are attached to a circuit card, the circuit card comprising at least one conductor for electrically connecting between one of the one or more series resonators and one of the one or more parallel resonators.

[0028] The first material stack includes a first piezoelectric element, the second material stack includes a second piezoelectric element, and the first piezoelectric element and the second piezoelectric element differ in at least one of the material, thickness, and orientation of a crystal axis of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1A is a schematic diagram of an exemplary RF ladder filter circuit including an acoustic wave resonator.

[0030] Figure 1B is a schematic diagram of an alternative embodiment of an RF ladder filter circuit incorporating an acoustic wave resonator.

[0031] Figure 2A is a simplified schematic cross-sectional view of a first acoustic wave resonator.

[0032] Figure 2B is a simplified schematic cross-sectional view of a second acoustic wave resonator.

[0033] Figure 3A is a simplified schematic cross-sectional view of a third acoustic wave resonator.

[0034] Figure 3B is a simplified schematic cross-sectional view of a fourth acoustic wave resonator.

[0035] Figure 4Ais a simplified schematic cross-sectional view of a fifth acoustic wave resonator.

[0036] Figure 4B is a simplified schematic cross-sectional view of a sixth acoustic wave resonator.

[0037] Figure 5 It is a simplified schematic plan view of a conventional ladder filter.

[0038] Figure 6 is a simplified schematic plan view of a split-step implementation of a bandpass filter.

[0039] Figure 7 yes Figure 6 A simplified schematic cross-sectional view of a split-step implementation of an exemplary bandpass filter.

[0040] Figure 8 is a graph comparing S12 for two implementations of an exemplary bandpass filter.

[0041] Fig. 9 is a graph of S12 for a split-step implementation of an exemplary bandpass filter.

[0042] Fig. 10A is a simplified schematic plan view of a two-chip duplexer.

[0043] Fig. 10B is a simplified schematic plan view of a split-step implementation of a duplexer.

[0044] Fig.11 is a simplified schematic plan view of another split-step implementation of a duplexer.

[0045] Fig.12 is a flow chart of a method for manufacturing a separate ladder filter device.

[0046] Throughout the specification, elements appearing in the drawings are assigned three-digit reference numerals, of which the two least significant digits are specific to the element and the one or two most significant digits are the figure number in which the element is first shown. Elements not described in conjunction with a drawing may be assumed to have the same characteristics and functions as previously described elements having the same reference numeral. DETAILED DESCRIPTION

[0047] Device Description

[0048] Figure 1AA simplified schematic circuit diagram of an exemplary RF filter circuit 100 is shown, which combines six acoustic wave resonators, labeled X1 to X6, arranged in a manner commonly referred to as a "ladder" configuration. Ladder filters of this configuration are commonly used for bandpass filters in communication devices. The filter circuit 100 can be, for example, a transmit filter or a receive filter for incorporation into a communication device. The filter circuit 100 is a two-port network in which one terminal of each port is typically connected to a signal ground. The filter circuit 100 includes three series resonators (X1, X3, and X5) connected in series between a first port (port 1) and a second port (port 2). Either port can be the input of the filter and the other port is the output. The filter circuit 100 includes three parallel resonators (X2, X4, and X6). Each parallel resonator is connected between the ground and the junction or input or output port of the adjacent series resonator. Figure 1A The schematic diagram is simplified in that passive components are not shown, such as the inductance inherent in the conductors interconnecting the resonators. The use of six acoustic wave resonators, three series resonators and three parallel resonators is exemplary. The bandpass filter circuit may include more or less than six resonators and more or less than three series resonators and three parallel resonators.

[0049] Figure 1B A simplified schematic circuit diagram of an alternative RF filter circuit 150 is shown. The filter circuit 150 is a two-port network in which the signal at each port is balanced, that is, the signals at the two terminals of each port are nominally equal in amplitude and 180 degrees out of phase. For the purposes of this patent, the RF filter circuit 150 is considered a ladder filter. Resonators X1a, X1b, X3a, X3b, X5a, and X5b are considered series resonators, while resonators X2, X4, and X6 are considered parallel resonators. The ladder filter circuit 150 is not commonly used, and all subsequent examples in this patent use the ladder filter circuit 150. Figure 1A Ladder filter configuration.

[0050] Each acoustic wave resonator X1 to X6 can be a bulk acoustic wave (BAW) resonator, a film bulk acoustic wave (FBAW) resonator, a surface acoustic wave (SAW) resonator, a temperature compensated surface acoustic wave resonator (TC-SAW), a bonded chip acoustic wave resonator, a transversely excited film bulk acoustic wave resonator (XBAR) as described in application Ser. No. 16 / 230,443, a solid-state mounted transversely excited film bulk acoustic wave resonator (SM-XBAR) as described in application Ser. No. 16 / 438,141, or other types of acoustic wave resonators. In a current filter, the acoustic wave resonators are usually resonators of the same type.

[0051] Each acoustic wave resonator exhibits a very high admittance at the resonant frequency and a very low admittance at the anti-resonant frequency above the resonant frequency. In short, each resonator is approximately a short circuit at its resonant frequency and approximately an open circuit at its anti-resonant frequency. Therefore, the transmission between Port 1 and Port 2 of the bandpass filter circuits 100 and 150 is very low at the resonant frequency of the parallel resonator and the anti-resonant frequency of the series resonator. In a typical step bandpass filter, the resonant frequency of the parallel resonator is less than the lower edge of the filter passband to produce a stopband at frequencies below the passband. The anti-resonant frequency of the parallel resonator is typically within the passband of the filter. In contrast, the anti-resonant frequency of the series resonator is greater than the upper edge of the passband to produce a stopband at frequencies above the passband. The resonant frequency of the series resonator typically falls within the passband of the filter. In some designs, the resonant frequency of one or more parallel resonators may be higher than the upper edge of the passband.

[0052] Filter devices, such as bandpass filter circuits 100 and 150, including acoustic wave resonators, are conventionally implemented using multiple layers of material, where the multiple layers of material are deposited on, bonded to, or otherwise formed on a substrate. The substrate and sequence of material layers are often referred to as a "stack" for forming acoustic wave resonators and filter devices. In this patent, the term "material stack" refers to an ordered sequence of material layers formed on a substrate, where the substrate is considered to be part of the material stack. The term "element" refers to a substrate or one of the layers in the material stack. At least one element (i.e., substrate or layer) in the material stack is a piezoelectric material, such as quartz, lithium niobate, lithium tantalate, lanthanum gallium silicate, gallium nitride, or aluminum nitride. When the piezoelectric material is a single crystal, the orientation of the X, Y, and Z crystal axes is known and consistent. One or more layers in the material stack, such as one or more conductor layers and / or dielectric layers, can be patterned using photolithography methods so that not all elements of the material stack are present at every point on the acoustic wave device.

[0053] Figure 2A is a schematic cross-sectional view of a first exemplary acoustic wave resonator 200. The first acoustic wave resonator 200 will be referred to herein as a "non-bonded SAW resonator" (with a bonded Figure 2BThe term "unbonded SAW resonator" is opposite to the "bonded chip resonator" described above). The "unbonded SAW resonator" is characterized by a conductor pattern 210 formed on a piezoelectric plate 205 that is not bonded to a thicker base or substrate. The term includes temperature compensated and non-temperature compensated SAW resonators. The conductor pattern 210 includes an interdigital transducer (IDT) formed on the surface of a plate 205 of a single crystal piezoelectric material. Dimension p is the spacing between the IDT fingers or the spacing between conductors. Dimension λ=2p is the wavelength of the sound wave propagating across the surface of the piezoelectric plate 205. When multiple unbonded SAW resonators 200 are combined to form a filter device, the resonant frequency of each resonator is set by selecting the spacing between each resonator. Dimension h is the thickness of the conductor pattern. A dielectric layer 215 with a thickness of td1 can be deposited above and between the conductors of the conductor pattern. The dielectric layer 215 can be, for example, a thin passivation layer to seal and protect the electrode pattern and the surface of the piezoelectric plate 205. In a TC-SAW resonator, the dielectric layer 215 may be a relatively thick layer, for example, SiO 2 layer, used to reduce the frequency temperature coefficient of the resonator.

[0054] The material stack for an unbonded SAW resonator (e.g., the first exemplary acoustic wave resonator 200) includes a piezoelectric plate 205, a conductor pattern 210, and a dielectric layer 215. The piezoelectric plate 205 is defined by the material type, thickness, and crystal axis orientation of the piezoelectric material. The conductor pattern 210 is defined by the thickness h and the material, which can be, for example, aluminum, copper, gold, molybdenum, tungsten, alloys, and combinations thereof. The dielectric layer 215 is defined by the thickness td1 and the material, which can be, for example, silicon dioxide or silicon nitride. When multiple unbonded SAW resonators 200 are incorporated into a filter device, the material stack may include Figure 2A For example, the filter device typically includes a second metal layer to increase the conductivity of the conductors interconnecting the resonators, and may include additional dielectric layers and / or a third metal layer of thick gold or solder to form bumps to interconnect the filter to an external circuit card.

[0055] Figure 2Bis a schematic cross-sectional view of a second exemplary acoustic wave resonator 220. The second acoustic wave resonator 220 will be referred to herein as a "bonded wafer resonator". The "bonded wafer resonator" is characterized by a thin wafer or plate 225 of a single crystal piezoelectric material bonded to a non-piezoelectric base 230. The thin wafer or plate 225 of a single crystal piezoelectric material may be bonded directly to the non-piezoelectric base 230, or bonded to the non-piezoelectric base 230 through one or more intermediate dielectric layers 240. The second acoustic wave resonator 220 may be, for example, a bonded wafer SAW resonator, an IHP (Incredibly High Performance) SAW resonator, or a plate wave resonator. The second acoustic wave resonator 220 includes a conductor pattern 235 including an IDT formed on a surface of the thin wafer 225 of a single crystal piezoelectric material. The thickness of the conductor pattern is dimension h (see Figure 2A ). Dimension tp is the thickness of the piezoelectric material wafer 225. Dimension p is the spacing of the IDT fingers or the spacing from conductor to conductor. Dimension λ=2p is the wavelength of the acoustic wave propagating across the surface of the piezoelectric wafer 225 or within the piezoelectric wafer 225. When multiple bonded wafer resonators 220 are combined to form a filter device, the resonant frequency of the various resonators is set by selecting the IDT spacing of each resonator. The thickness is td1 (see Figure 2A ) can be deposited on and between the conductors of the conductor pattern as described above. A second dielectric layer 240 having a thickness of td2 can be disposed between the wafer 225 and the base 230. In some cases, two dielectric layers can be disposed between the wafer 225 and the base 230.

[0056] The material stack for bonding a chip resonator, such as the second exemplary acoustic wave resonator 220, includes a base 230, one or more underlying dielectric layers 240 (if present), a piezoelectric chip 225, a conductor pattern 235, and a dielectric layer 245. The base 230 is defined by material and thickness. The underlying dielectric layers 240 are defined by the material type and thickness td2 of each layer. The piezoelectric chip 225 is defined by the material type, thickness tp, and orientation of the crystal axis of the piezoelectric material. The conductor pattern 235 is defined by the thickness h (see Figure 2A ) and materials. Dielectric layer 245 is defined by thickness td1 and material. When multiple bonded wafer resonators 220 are combined into a filter, the material stack may include additional layers as previously described.

[0057] Figure 3Ais a schematic cross-sectional view of a third exemplary acoustic wave resonator 300. The third acoustic wave resonator 300 will be referred to herein as a "floating diaphragm resonator". The floating diaphragm resonator is characterized in that a thin diaphragm 335 of a single crystal piezoelectric material floats above a cavity 330 formed in a non-piezoelectric base 315. The third acoustic wave resonator 300 may be, for example, an XBAR resonator or other type of acoustic wave resonator as described in application Ser. No. 16 / 230,443. The third acoustic wave resonator 300 includes a conductor pattern 305 including an IDT formed on a surface of a thin wafer 310 of a single crystal piezoelectric material, the conductor pattern being attached or bonded to a non-piezoelectric base 315. When the third acoustic wave resonator is a plate wave resonator, the conductor pattern may include a Bragg reflector ( Figure 3A 310 and the pedestal 315. A dielectric layer 320 or layers may be present between the wafer 310 and the pedestal 315. A cavity 330 is formed in the pedestal 315 and the dielectric layer(s) 320 (if present) such that a portion of the wafer 310 forms a diaphragm 335 that spans the cavity 330. The fingers of the IDT are disposed on the diaphragm 335. The dielectric layer 325 may be deposited over and between the fingers of the conductor pattern 305.

[0058] The material stack for a floating diaphragm resonator such as the third exemplary acoustic wave resonator 300 includes a base 315, one or more underlying dielectric layers 320 (if present), a piezoelectric wafer 310, a conductor pattern 305, and a dielectric layer 325. The base 315 is defined by a material and a thickness. The underlying dielectric layer 320 is defined by the material type and thickness td2 of each layer. The piezoelectric wafer 310 is defined by the material type, thickness tp, and orientation of the crystal axis of the piezoelectric material. The conductor pattern 305 is defined by its thickness and material. The dielectric layer 325 is defined by a thickness td1 and a material. When multiple acoustic wave resonators 300 are incorporated into a filter, the material stack may include additional layers as described above.

[0059] Figure 3B is a schematic cross-sectional view of a fourth exemplary acoustic wave resonator 350. The fourth acoustic wave resonator 350 will be referred to herein as a "solid-state mounted membrane resonator". The solid-state mounted membrane resonator is characterized by a conductor pattern 355, which includes an IDT formed on the surface of a thin film 360 of a single crystal piezoelectric material supported by a non-piezoelectric base 365, with an acoustic Bragg reflector 370 sandwiched between the membrane 360 ​​and the base 365. The acoustic Bragg reflector 370 includes multiple layers that alternate between a first material having a high acoustic impedance and a second material having a low acoustic impedance. The acoustic Bragg reflector 370 is configured to reflect and confine acoustic waves generated by the membrane 360. A dielectric layer 375 can be deposited on and between the fingers of the conductor pattern 355.

[0060] The material stack for the solid-state mounted film resonator 350 includes a base 365, an acoustic Bragg reflector 370, a piezoelectric film 360, a conductor pattern 355, and a dielectric layer 375. The base 365 is defined by a material and a thickness. The acoustic Bragg reflector 370 is defined by the first and second material types of each layer, the number of layers, and the thickness of each layer. The piezoelectric film 360 is defined by the material type, thickness tp, and orientation of the crystal axis of the piezoelectric material. The conductor pattern 355 is defined by its thickness and material. The dielectric layer 375 is defined by a thickness td1 and a material. When multiple solid-state mounted film resonators are incorporated into a filtering device, the material stack may include additional layers as described above.

[0061] Figure 4A 4 is a schematic cross-sectional view of a fifth exemplary acoustic wave resonator 400. The fifth acoustic wave resonator 400 is a film bulk acoustic resonator (FBAR). The fifth acoustic wave resonator 400 includes a thin wafer or film 405 of a single crystal piezoelectric material sandwiched between an upper conductor 420 and a lower conductor 415, respectively. The sandwich structure is supported by a non-piezoelectric base 410. A cavity 425 is formed in the base 410 so that a portion of the sandwich structure 415 / 405 / 420 forms a diaphragm across the cavity 425.

[0062] The material stack of FBAR 400 includes base 410, lower conductor layer 415, piezoelectric wafer or film 405, and upper conductor layer 420. Base 410 is defined by material and thickness. Lower conductor layer 415 is defined by material type and thickness. Piezoelectric wafer or film 405 is defined by material type, thickness and orientation of crystal axis of piezoelectric material. Upper conductor layer 420 is defined by its thickness and material. When multiple FBARs 400 are incorporated into a filter, the material stack may include additional layers as previously described.

[0063] Figure 4B 4 is a schematic cross-sectional view of a sixth exemplary acoustic wave resonator 450. The sixth acoustic wave resonator will be referred to herein as a "solid-state assembled thin film bulk acoustic wave resonator" (SM-FBAR). The sixth acoustic wave resonator 450 includes a thin wafer or film 455 of a single crystal piezoelectric material sandwiched between an upper conductor 470 and a lower conductor 465, respectively. The sandwich structure is supported by a non-piezoelectric base 460. An acoustic Bragg reflector 475 is sandwiched between the sandwich structure 470 / 455 / 465 and the base 460. The acoustic Bragg reflector 475 includes multiple layers that alternate between a first material having a high acoustic impedance and a second material having a low acoustic impedance. The acoustic Bragg reflector 475 is configured to reflect and confine the acoustic waves generated by the sandwich structure 470 / 455 / 465.

[0064] The material stack for SM-FBAR 450 includes base 460, acoustic Bragg reflector 475, lower conductor layer 465, piezoelectric wafer or film 455, and upper conductor layer 470. Base 460 is defined by material and thickness. Acoustic Bragg reflector 475 is defined by the first and second material types, the number of layers, and the thickness of each layer. Lower conductor layer 465 is defined by material type and thickness. Piezoelectric wafer or film 455 is defined by the material type, thickness, and crystal axis orientation of the piezoelectric material. Upper conductor layer 470 is defined by its thickness and material. When multiple SM-FBARs 450 are incorporated into a filter, the material stack may include additional layers as previously described.

[0065] Figures 2A to 4B The acoustic wave resonators shown are not an all-inclusive list of acoustic wave resonator types. Other types of acoustic wave resonators with other material stacks can be used for filters. In addition, Figures 2A to 4B The cross-sectional views do not necessarily show all layers in the corresponding material stack. For example, additional layers may be present to promote adhesion between other layers, prevent chemical interactions between other layers, or passivate and protect other layers.

[0066] Figure 5 is an exemplary schematic plan view of a conventional embodiment of a bandpass filter 500, which has the same schematic diagram as the bandpass filter circuit 100 of FIG. In the filter 500, all six acoustic wave resonators X1-X6 are formed on a common chip 510. All of the acoustic wave resonators X1-X6 can be non-bonded SAW resonators, bonded chip resonators, floating diaphragm resonators, solid-state mounted membrane resonators, FBARs, SM-FBARs, or some other type of acoustic wave resonators. All of the acoustic wave resonators X1 to X6 are typically the same type of resonator. For ease of drawing, Figure 5 All resonators X1-X6 have the same size. This situation rarely occurs in practical filters.

[0067] The acoustic wave resonators X1-X6 are interconnected by conductors (e.g., conductor 530) formed on substrate 510. The filter 500 is electrically connected to a system outside the filter through pads (e.g., pads 520). For example, each pad can be or have solder or gold bumps to connect to a circuit board (not shown). In addition to establishing electrical connections, pads and bumps are typically the primary means of removing heat from the filter 500.

[0068] When multiple acoustic wave resonators are formed on the same chip, the manufacturing process and material stack for all multiple resonators are essentially the same. In particular, the piezoelectric element within the material stack (i.e., the plate, wafer, or film of piezoelectric material) is the same for all resonators. However, the requirements for parallel and series resonators are generally different, as shown in the following table:

[0069]

[0070] It may not be possible to select a material stack that is most suitable or even sufficient for all resonators in a filter.

[0071] Figure 6 is an exemplary schematic plan view of a separated ladder filter 600 having Figure 1A The same schematic diagram of the ladder filter circuit 100 is shown. Figure 5 Unlike the conventional filter 500 shown, the series resonators X1, X3, and X5 of the separated ladder filter 600 are manufactured on a first chip 610, and the parallel resonators X2, X4, and X6 of the separated ladder filter 600 are manufactured on a second chip 640. In each chip 610 and 640, the acoustic wave resonators are interconnected by conductors formed on the corresponding chips, such as conductors 630. The chips 610 and 640 are electrically connected to each other and to the system outside the filter through pads such as pads 620. Each pad can be, for example, a solder or gold bump, or interacts with a solder or gold bump to connect to a circuit board (not shown).

[0072] The electrical connection 650 between the series resonator on the first chip 610 and the parallel resonator on the second chip 640 is shown as a thick dashed line. The connection 650 is made, for example, by a conductor on a circuit card on which the first and second chips are mounted. In this context, the term "circuit card" refers to a basic planar structure containing conductors to connect the first and second chips to each other and to a system outside the bandpass filter 600. The circuit card can be, for example, a single-layer or multi-layer printed wiring board, a low temperature co-fired ceramic (LTCC) card, or other type of circuit card. The traces on the circuit card may have very low resistance, so the losses in the traces can be ignored. The inductance of the electrical connection 650 between the series resonator and the parallel resonator can be compensated in the design of the acoustic wave resonator. In some cases, the inductance of the electrical connection 650 can be used to improve the performance of the filter, for example, by reducing the resonant frequency of one or more parallel resonators to increase the filter bandwidth to improve the performance of the filter.

[0073] In the exemplary split ladder filter 600, all series resonators are on the first chip and all parallel resonators are on the second chip. However, this is not necessarily the case. In some filters, the first chip may contain less than all series resonators and / or the second chip may contain less than all parallel resonators.

[0074] Figure 7is a schematic cross-sectional view of a split ladder filter 700, which may be the split ladder filter 600. The split ladder filter 700 includes a first chip 710 and a second chip 740 attached to and interconnected by a circuit card 770. In this example, the first and second chips 710, 740 are mounted to the circuit card 770 in a "flip chip" manner. The electrical connection between the first and second chips 710, 740 and the circuit card 770 is made by solder or gold bumps, such as bumps 720. The electrical connection between the first chip 710 and the second chip 740 is made by conductors on or inside the circuit card 770, such as conductor 750. The first and second chips 710, 740 can be mounted on and / or connected to the circuit card 770 in some other way.

[0075] A benefit of split ladder filters (e.g., split ladder filters 600 and 700) is that stacks of different materials can be used for series resonators and parallel resonators. A first material stack can be used for a first chip containing some or all of the series resonators, while a second material stack can be used for a second chip containing some or all of the parallel resonators. The first and second material stacks can be different. This allows the first and second material stacks for the series resonators and the parallel resonators to be optimized separately.

[0076] Two material stacks are considered different if they differ in at least one aspect of at least one element within the stack. The differences between the material stacks can be, for example, the order of the elements or different material types, thicknesses or other parameters of at least one element in the stack. Typically, the first material stack comprises a first piezoelectric element and the second material stack comprises a second piezoelectric element that differs from the first piezoelectric element in at least one of the material, thickness and orientation of the crystal axes of the material.

[0077] like Figure 2A As shown, when the split ladder filter 600 / 700 is incorporated into a non-combined SAW resonator, the first material stack and the second material stack can differ in one or more of the following characteristics: the material type, thickness and orientation of the crystal axis of the piezoelectric plate 205; the material and / or thickness h of the conductor pattern 210; and the thickness td1 and material of the dielectric layer 215.

[0078] When the split ladder filter 600 / 700 is combined as Figure 2B When the combined chip resonator is shown, the first material stack and the second material stack can differ in one or more of the following characteristics: the material and thickness of the base 230; the number of underlying dielectric layers 240 (if any) and the material and thickness td2 of each layer; the material type, thickness tp and crystal axis orientation of the piezoelectric chip 225; the thickness h and material of the conductor pattern 235; and the thickness td1 and material of the dielectric layer 245.

[0079] When the split ladder filter 600 / 700 is combined as Figure 3A In the floating diaphragm resonator shown, the first material stack and the second material stack may differ in one or more of the following characteristics: the material and thickness of the base 315; the number of underlying dielectric layers 320 (if any) and the material and thickness td2 of each layer; the material type, thickness tp and crystal axis orientation of the piezoelectric wafer 310; the thickness h and material of the conductor pattern 305; and the thickness td1 and material of the dielectric layer 325.

[0080] When the split ladder filter 600 / 700 is combined as Figure 3B In the solid-state assembled membrane resonator shown, the first material stack and the second material stack may differ in one or more of the following characteristics: the material and thickness of the base 365; the number of layers in the acoustic Bragg reflector 370 and the material and thickness of each layer; the material type, thickness tp and crystal axis orientation of the piezoelectric chip 360; the thickness h and material of the conductor pattern 365; and the thickness td1 and material of the dielectric layer 375.

[0081] When the split ladder filter 600 / 700 is incorporated into Figure 4A When the FBAR is shown, the first material stack and the second material stack can differ in one or more of the following characteristics: the material and thickness of the base 410; the material and thickness of the lower conductor 415; the material type, thickness tp and crystal axis orientation of the piezoelectric wafer 405; and the thickness and material of the upper conductor 420.

[0082] When the split ladder filter 600 / 700 is incorporated into Figure 4B In the SM-FBAR shown, the first material stack and the second material stack may differ in one or more of the following characteristics: the material and thickness of the base 460; the number of layers in the acoustic Bragg reflector 475 and the material and thickness of each layer; the material and thickness of the lower conductor 465; the material type, thickness tp and crystal axis orientation of the piezoelectric wafer 455; and the thickness and material of the upper conductor 470.

[0083] The preceding six paragraphs do not necessarily identify the difference between the first material stack and the second material stack of the split ladder filter. The first material stack and the second material stack may differ in one or more parameters in addition to the parameters identified herein, or the first material stack and the second material stack may differ in one or more parameters other than the parameters identified herein. The type of resonator is not limited to Figures 2A to 4B Furthermore, the series resonator and the parallel resonator do not have to be the same type of resonator.

[0084] Example 1

[0085] A desirable characteristic of filters for portable devices is the stability of the filter passband over a wide temperature range. A technique to achieve at least part of this goal is to use a thin wafer of piezoelectric material to make filters with bonded wafer resonators, where the piezoelectric material is bonded to a base (e.g., a silicon substrate) that has a low coefficient of thermal expansion and a high thermal conductivity. Bonded wafer SAW filters have a lower temperature rise at a given power input and a reduced sensitivity of the passband frequency to temperature compared to filters using unbonded SAW resonators.

[0086] One disadvantage of bonded wafer SAW resonators is the presence of parasitic acoustic modes that can propagate within the piezoelectric material or into the silicon wafer or other substrate. A key element in designing a bandpass filter using bonded wafer resonators is to ensure that the spurious modes appear at frequencies far from the filter passband. The cross-sectional structure and material stack of a bonded wafer SAW resonator is similar to Figure 2B resonator 250.

[0087] Figure 8 800 is a graphical representation of the S12 magnitude of two bonded wafer SAW filters fabricated using lithium tantalate (LT) wafers bonded to a silicon submount. S12 is the transmission between the first and second ports of the filter. The dashed line 810 is the S12 plot for a filter fabricated on a 42 degree Y-cut LT wafer. The dashed line 820 is the S12 plot for a filter fabricated on a 46 degree Y-cut LT wafer. The bold line 830 defines the requirements for the LTE (Long Term Evolution) Band 2 transmission filter (insertion loss less than 2 dB over the transmission band from 1850 MHz to 1910 MHz).

[0088] When the filter is fabricated at 42 degrees LT (dash-dot line 810), parasitic modes appear at frequencies near the anti-resonance frequency of the series resonator in the filter. These parasitic modes degrade the S12 near the upper edge of the filter passband between 1902 MHz and 1915 MHz (and correspondingly increase insertion loss).

[0089] When the filter is fabricated at 46 degrees LT (dashed line 820), parasitic modes appear at frequencies near the resonant frequency of the parallel resonator. These parasitic modes degrade the S12 (and correspondingly increase the insertion loss) between 1845 MHz and 855 MHz. None of these filters meet the requirement of less than 2 dB insertion loss over the LTE Band 2 transmission band.

[0090] Fig. 9900 (curve 910) is a graphical representation of the magnitude of S12 for a split-step LTE Band 2 transmit filter fabricated on two chips, each having a lithium tantalate (LT) wafer bonded to a silicon submount. The first chip contains a series resonator fabricated at 46 degrees LT. The second chip contains a parallel resonator fabricated at 42 degrees LT. The material stacks for the first and second chips differ in at least the orientation of the crystal axes of the respective LT wafers, as well as in many other respects.

[0091] Using a 46 degree LT for the series resonator avoids losses at the upper edge of the passband due to parasitic modes evident in curve 810. Using a 42 degree LT for the parallel resonator avoids losses at the lower edge of the passband due to parasitic modes evident in curve 820. Figure 8 The performance of any conventional (i.e., single-chip) ladder filter is compared to that of Fig. 9 As shown, the split ladder filter meets the LTE Band 2 transmission filter insertion loss requirement (bold line 930).

[0092] Example 2

[0093] For most acoustic wave resonators, increased temperature causes both the resonant frequency and the anti-resonant frequency to shift to lower frequencies. The reduction in the resonant frequency of the parallel resonator increases the margin between the lower edge of the filter passband and the lower edge of the actual frequency band. Therefore, the effect of temperature on the parallel resonator may be small. In contrast, the reduction in the anti-resonant frequency of the series resonator reduces the margin between the upper edge of the filter passband and the upper edge of the actual frequency band. This effect is accompanied by an increase in power loss in the series resonator. Therefore, compared with the parallel resonator, the advantages of the bonded chip resonator (low frequency temperature coefficient and high thermal conductivity to limit temperature rise) are more important for the series resonator. A separate ladder filter including a first chip with a bonded chip series resonator and a second chip with a non-bonded SAW parallel resonator provides a lower cost than the previous example 1 while maintaining the benefits of using a bonded chip series resonator.

[0094] Example 3

[0095] Many frequency bands used by portable communication devices are "frequency division duplex" (FDD) bands, that is, separate frequency ranges or bands are used for signals transmitted from and received by the device. A duplexer is a filter subsystem that is used to separate the transmit band from the receive band. Typically, a duplexer includes a transmit filter that receives a transmit signal from a transmitter and passes the filtered transmit signal to an antenna, and a receive filter that receives a receive signal from an antenna and passes the filtered receive signal to a receiver.

[0096] The duplexer can be implemented as two filters on a common chip, where the transmit filter and the receive filter are stacked using the same material. Alternatively, the duplexer 1000 can be implemented with the transmit filter and the receive filter on separate chips, such as Fig. 10A As shown. The first chip 1010 contains the transmit filter and the second chip 1020 contains the receive filter. The pads on the chips 1010, 1020 are connected to the circuit card as described above. The pad label "Tx" is the input from the transmitter. The pad labeled "Rx" is the output of the receiver. The pad labeled "A" is connected to the antenna. The pad labeled "G" is grounded. Fig. 10A The concept of a dual-chip duplexer is shown, but a specific duplexer design is not shown. For ease of manufacturing, the transmit filter on the first chip 1010 is connected to the Figure 5 The filters shown are the same, and the receive filter on the second chip 1020 is Figure 5 The image of the filter.

[0097] Implementing a duplexer with transmit and receive filters on different chips allows the material stackup of the two filters to be different. A two-chip implementation may be suitable for frequency division duplexing bands where the transmit and receive bands are far apart. For example, LTE Band 4 has a 400MHz separation between the transmit band (1710MHz to 1755MHz) and the receive band (2110MHz to 2155MHz). By implementing an LTE Band 4 duplexer with transmit and receive filters on different chips, the material stackup of the two filters can be optimized for their respective frequency ranges.

[0098] Fig. 10B is an exemplary schematic plan view of a split ladder duplexer 1050 including a transmit filter and a receive filter, each filter having a Figure 1A The same schematic diagram of the bandpass filter circuit 100. The transmitting filter includes series resonators XT1, XT3, XT5 and parallel resonators XT2, XT4, XT6. The receiving filter includes series resonators XR1, XR3 and XR5 and parallel resonators XR2, XR4 and XR6. Fig. 10ACompared to the dual-chip duplexer 1000 shown, the series resonators XT1, XT3, XT5, XR1, XR3, XR5 of the transmit filter and the receive filter are manufactured on the first chip 1060. The parallel resonators XT2, XT4, XT6, XR2, XR4, XR6 of the transmit filter and the receive filter are manufactured on the second chip 1070. The chips 1060 and 1070 are electrically connected to each other and connected to the system outside the filter through pads and a circuit card as described above. For example, each pad can be a solder or gold bump or interact with it to connect to a circuit card (not shown). The electrical connection 650 between the series resonator on the first chip 1060 and the parallel resonator on the second chip 1070 is shown in bold dashed lines. The connection 650 is formed, for example, by a conductor on a circuit card on which the first and second chips 1060 and 1070 are mounted.

[0099] The transmit filter may be, for example, a combination of Figure 8 and Fig. 9 LTE Band 2 transmit split ladder filter is described. The receive filter may be similar to a split ladder filter with a passband from 1930 MHz to 1990 MHz.

[0100] Example 4

[0101] Fig.11 is an exemplary schematic plan view of another split ladder duplexer 1100 including a transmit filter and a receive filter, each filter having a Figure 1A The same schematic diagram of the bandpass filter circuit 100 of FIG. The transmit filter includes series resonators XT1, XT3, XT5 and parallel resonators XT2, XT4, XT6. The receive filter includes series resonators XR1, XR3 and XR5 and parallel resonators XR2, XR4 and XR6. The series resonators XT1, XT3, XT5 of the transmit filter are manufactured on a first chip 1060. The parallel resonators XT2, XT4, XT6 of the transmit filter and all the resonators XR1, XR2, XR3, XR4, XR5, XR6 of the receive filter are manufactured on a second chip 1070. The chips 1060, 1070 are electrically connected to each other and are connected to the system outside the filter as a circuit card through pads and as described above.

[0102] The series resonators XT1, XT3, XT5 of the transmit filter on the first chip 1160 have high power consumption compared to the resonators on the second chip 1120. Therefore, the first chip may have a material stack that allows the resonator to dissipate heat effectively. The series resonators XT1, XT3, XT5 of the transmit filter may be, for example, bonded wafer resonators or solid-state assembled membrane resonators. The second chip, where heat dissipation is less important, may be manufactured using different types of resonators. The resonators on the second chip may be, for example, non-bonded SAW resonators.

[0103] Method Description

[0104] Fig.12 is a flow chart of a method 1200 for manufacturing a split ladder filter device, which may be the split ladder filter device 600, 700, or 1050. The method 1200 begins at 1210 and ends at 1290, with the filter device being manufactured.

[0105] At 1220, a first chip is fabricated using the first material stack. The first chip includes one, some, or all of the series resonators of the filter device. The first chip may be part of a first multi-chip wafer, such that multiple copies of the first chip are produced each time step 1220 is repeated. In this case, individual chips may be cut from the wafer and tested as part of the actions at 1220.

[0106] At 1230, a second chip is fabricated using a second material stack that is different from the first material stack. The second chip includes one, some, or all of the parallel resonators of the filter device. The second chip can be part of a second multi-chip wafer, so that multiple copies of the second chip are produced each time step 1230 is repeated. In this case, individual chips can be cut from the wafer and tested as part of the actions at 1230.

[0107] At 1240, a circuit card is manufactured. The circuit card may be, for example, a printed wiring board or an LTCC card or some other form of circuit card. The circuit card may include one or more conductors for making at least one electrical connection between a series resonator on a first chip and a parallel resonator on a second chip. The circuit may be part of a large substrate such that multiple copies of the circuit card are produced during each repetition of step 1240. In this case, individual circuit cards may be cut from the substrate and tested as part of the actions at 1240. Alternatively, individual circuit cards may be cut from the substrate after the chips are attached to the circuit card at 1250, or after the devices are packaged at 1260.

[0108] At 1250, the separate first and second chips are assembled to a circuit card (which may or may not be part of a larger substrate) using known processes. For example, the first and second chips may be mounted to the circuit card in a "flip chip" fashion using solder or gold bumps or balls to establish electrical, mechanical, and thermal connections between the chips and the circuit card. The first and second chips may be assembled to the circuit card in some other manner.

[0109] The filter device is completed at 1260. Completing the filter device at 1260 includes packaging and testing. Completing the filter device at 1260 may include cutting individual circuit card / chip assemblies from a larger substrate before or after packaging.

[0110] Conclusion

[0111] Throughout the specification, the illustrated embodiments and examples should be considered as examples, rather than limitations on the disclosed or claimed devices and processes. Although many of the examples provided herein involve specific combinations of method actions or system elements, it should be understood that those actions and those elements can be combined in other ways to achieve the same goal. With respect to the flow chart, additional steps and fewer steps can be taken, and the steps shown can be combined or further refined to achieve the methods described herein. The actions, elements and features discussed only in conjunction with one embodiment are not intended to exclude their similar effects in other embodiments. As used herein, "multiple" refers to two or more. As used herein, a "group" of items may include one or more such items. As used herein, whether in a written specific embodiment or in a claim, the terms "including", "comprising", "carrying", "having", "containing", "involving", etc. should be understood as open, that is, referring to including but not limited to. With respect to the claims, only the transition phrases "consisting of..." and "consisting essentially of..." are closed or semi-closed transition phrases. Ordinal numbers used in claims, such as "first", "second", "third", etc., are used to modify claim elements, which do not in themselves indicate the priority, order, or sequence of one claim element over another claim element, but are only used to distinguish one claim element with the same name from another element with the same name (but with ordinal numbers), thereby distinguishing the claim elements. As used herein, "and / or" means that the listed items are alternatives, but alternatives also include any combination of the listed items.

Claims

1. A filter device, include: A first chip, comprising a first interdigital transducer IDT of a first BAW resonator located at a first piezoelectric plate, wherein the first IDT is disposed on a portion of the first piezoelectric plate above a first cavity of the first BAW resonator; as well as A second chip including a second IDT of a second BAW resonator formed at a second piezoelectric plate, the second IDT being disposed on a portion of the second piezoelectric plate above a second cavity of the second BAW resonator; as well as a circuit card coupled to the first chip and the second chip, Wherein, the thickness of the first piezoelectric plate is greater than the thickness of the second piezoelectric plate.

2. The filter device according to claim 1, in: The first chip includes a series resonator of a ladder filter circuit, and The second chip includes a parallel resonator of the ladder filter circuit.

3. The filter device according to claim 1, in, The circuit card includes at least one electrical connection between the first BAW resonator of the first chip and the second BAW resonator of the second chip.

4. The filter device according to claim 1, in, The first piezoelectric plate and the second piezoelectric plate differ in at least one of material and orientation of a crystal axis of the material.

5. The filter device according to claim 1, in, The thickness of the IDT of the first BAW resonator is different from the thickness of the IDT of the second BAW resonator.

6. The filter device according to claim 1, in, A material of the IDT of the first BAW resonator is different from a material of the IDT of the second BAW resonator.

7. The filter device according to claim 1, in, The IDT of the first BAW resonator is covered by a dielectric layer having a thickness different from a thickness of a dielectric layer covering the IDT of the second BAW resonator.

8. The filter device according to claim 1, in, The IDT of the first BAW resonator is covered by a dielectric layer whose material is different from that of the dielectric layer covering the IDT of the second BAW resonator.

9. The filter device according to claim 1, in, The thickness of a dielectric layer formed between the IDTs of the first BAW resonator is different from the thickness of a dielectric layer formed between the IDTs of the second BAW resonator.

10. The filter device according to claim 1, in, The first chip further includes a first pedestal and a first dielectric layer located above the first pedestal, wherein the first cavity is formed in the first dielectric layer.

11. The filter device according to claim 10, in, The second chip includes a second base and a second dielectric layer located over the second base, wherein the second cavity is formed in the second dielectric layer.

12. The filter device according to claim 11, in, The first BAW resonator and the second BAW resonator are different in one or more of the following aspects: the first pedestal and the second pedestal are made of different materials, or the first pedestal and the second pedestal have different thicknesses.

13. The filter device according to claim 10, in, The first base includes a non-piezoelectric base.

14. The filter device according to claim 11, in, The second base includes a non-piezoelectric base.

15. The filter device according to claim 1, in, The first BAW resonator is a floating diaphragm resonator.

16. The filter device according to claim 1, in, The second BAW resonator is a floating diaphragm resonator.

17. The filter device according to claim 1, in, The first BAW resonator is a solid-state mounted lateral excited FLAW resonator.

18. The filter device according to claim 1, in, The second BAW resonator is a solid-state mounted lateral excitation thin film BAW resonator.

19. The filter device according to claim 1, in, The first BAW resonator is a laterally excited thin film BAW resonator.

20. The filter device according to claim 1, in, The second BAW resonator is a laterally excited thin film BAW resonator.

21. The filter device according to claim 1, in, The circuit card electrically connects the first BAW resonator of the first chip and the second BAW resonator of the second chip through gold bumps and traces.

22. The filter device according to claim 1, in, The first chip and the second chip are connected to form a ladder filter circuit, wherein in the ladder filter circuit, the first BAW resonator is a series resonator, and the second BAW resonator is a parallel resonator.

23. The filter device according to claim 22, in, The series resonator is one of a plurality of series resonators all located on the first chip.

24. The filter device according to claim 22, in, The parallel resonator is one of a plurality of parallel resonators all located on the second chip.

25. The filter device according to claim 1, in, The circuit card electrically connects the first BAW resonator of the first chip and the second BAW resonator of the second chip through a metal layer to interconnect the first BAW resonator and the second BAW resonator.

26. A filter device, include: A first bulk acoustic wave resonator on a first chip, comprising: a first non-piezoelectric base; a first dielectric layer on the first non-piezoelectric base; a first piezoelectric plate on the first dielectric layer; and a first interdigital transducer IDT at the first piezoelectric plate; A second BAW resonator on a second chip, comprising: a second non-piezoelectric base; a second dielectric layer on the second non-piezoelectric base; a second piezoelectric plate on the second dielectric layer; a second interdigital transducer IDT at the second piezoelectric plate; and a circuit card electrically coupling the first chip and the second chip, Wherein, the thickness of the first piezoelectric plate is greater than the thickness of the second piezoelectric plate.

27. The filter device according to claim 26, in: The first BAW resonator is a series resonator of a ladder filter circuit, and The second BAW resonator is a parallel resonator of the ladder filter circuit.

28. The filter device according to claim 26, in, The circuit card includes at least one electrical connection between the first BAW resonator of the first chip and the second BAW resonator of the second chip.

29. The filter device according to claim 26, in, The first piezoelectric plate and the second piezoelectric plate differ in at least one of material and orientation of a crystal axis of the material.

30. The filter device according to claim 26, in, The thickness of the first IDT is different from the thickness of the second IDT.

31. The filter device according to claim 26, in, The material of the first IDT is different from the material of the second IDT.

32. The filter device according to claim 26, in, The first IDT is covered by a third dielectric layer having a thickness different from that of a fourth dielectric layer covering the second IDT.

33. The filter device according to claim 26, in, The first IDT is covered by a third dielectric layer whose material is different from that of the fourth dielectric layer covering the second IDT.

34. The filter device according to claim 26, in, The thickness of the third dielectric layer formed between the first IDTs is different from the thickness of the fourth dielectric layer formed between the second IDTs.

35. The filter device according to claim 26, in, The first BAW resonator and the second BAW resonator are different in one or more of the following aspects: the first non-piezoelectric base and the second non-piezoelectric base are made of different materials, or the first non-piezoelectric base and the second non-piezoelectric base have different thicknesses.

36. The filter device according to claim 26, in, The first BAW resonator is a floating diaphragm resonator.

37. The filter device according to claim 26, in, The second BAW resonator is a floating diaphragm resonator.

38. The filter device according to claim 26, in, The first BAW resonator is a solid-state mounted lateral excited FLAW resonator.

39. The filter device according to claim 26, in, The second BAW resonator is a solid-state mounted lateral excitation thin film BAW resonator.

40. The filter device according to claim 26, in, The first BAW resonator is a laterally excited thin film BAW resonator.

41. The filter device according to claim 26, in, The second BAW resonator is a laterally excited thin film BAW resonator.

42. The filter device according to claim 26, in, The circuit card electrically connects the first BAW resonator of the first chip and the second BAW resonator of the second chip through gold bumps and traces.

43. The filter device according to claim 26, in, The circuit card is a substantially planar structure that includes conductors to connect the first chip and the second chip to each other.

44. The filter device according to claim 26, in, The first chip and the second chip are connected to form a ladder filter circuit, wherein in the ladder filter circuit, the first BAW resonator is a series resonator and the second BAW resonator is a parallel resonator.

45. The filter device according to claim 44, in, The series resonator is one of a plurality of series resonators all located on the first chip.

46. ​​The filter device according to claim 44, in, The parallel resonator is one of a plurality of parallel resonators all located on the second chip.

47. The filter device according to claim 26, in, The circuit card electrically connects the first BAW resonator of the first chip and the second BAW resonator of the second chip through a metal layer to interconnect the first BAW resonator and the second BAW resonator.

48. A method of producing a filter device, include: manufacturing a first chip having a first material stack, the first chip containing one or more series resonators of a ladder filter circuit, wherein the first material stack includes a first piezoelectric plate element, and wherein the one or more series resonators are floating diaphragm resonators; and manufacturing a second chip having a second material stack, the second chip comprising one or more parallel resonators of the ladder filter circuit, wherein the second material stack comprises a second piezoelectric plate element, and wherein the one or more parallel resonators are floating diaphragm resonators, and The first material stack and the second material stack have the following difference: the thickness of the first piezoelectric plate element is different from the thickness of the second piezoelectric plate element.

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