A temperature compensation and control type bulk acoustic wave resonator and a preparation method thereof

Abstract

This invention discloses a temperature-compensated and temperature-controlled bulk acoustic wave resonator (FBAR), comprising a substrate, a resonant structure, and at least one micro-hotplate structure. The resonant structure and the at least one micro-hotplate structure are vertically adjacent, and the substrate is vertically adjacent to the resonant structure, or the substrate and the micro-hotplate structure are vertically adjacent. The micro-hotplate structure provides temperature compensation, temperature regulation, and temperature measurement, thereby enabling control of the device's frequency offset. This temperature-compensated and temperature-controlled FBAR achieves low-power temperature compensation and operating temperature control, ensuring that the FBAR device's operating temperature is unaffected by external temperature. Precise frequency offset control is achieved through temperature compensation and operating temperature control.

Description

Technical Field

[0001] This invention belongs to the field of filter device technology, specifically relating to a temperature-compensated and temperature-controlled bulk acoustic resonator and its fabrication method. Background Technology

[0002] With the rapid development and advancement of wireless communication technology, the performance requirements for radio frequency (RF) front-end devices, especially filters, in the communication field are becoming increasingly stringent. An ideal RF filter needs to possess: high selectivity, low insertion loss, high power capacity, high temperature stability, small size, light weight, low cost, and suitability for mass production. Traditional RF filter technologies (such as dielectric filters, cavity filters, and early surface acoustic wave (SAW) filters) are gradually facing bottlenecks in meeting these requirements, particularly in combining high frequency, small size, and low loss. Thin-film bulk acoustic resonators (FBARs), with their advantages of high Q value, high power capacity, and small size at high frequencies, have become a hot research area in recent years, showing broad application prospects and a huge commercial market in high-frequency communication.

[0003] The basic structure of a FBAR consists of a sandwich resonant structure composed of upper and lower electrodes and a piezoelectric layer in between, along with a substrate. The basic principle is that acoustic waves in the sandwich structure reflect back and forth, forming standing waves to achieve a filtering effect. Typically, the air above the device blocks the upward propagation of acoustic waves, achieving acoustic wave reflection on the upper electrode side. For leakage towards the substrate side, special structures using air or acoustic wave reflective layers are typically used to intercept and reflect the acoustic waves. Based on the different acoustic wave blocking and reflection structures on the lower side of the sandwich structure, thin-film bulk acoustic resonators are classified into back-etched, air-gap, and solid-state assembled types. The back-etched type achieves contact between air and the lower side of the sandwich resonant structure by etching away the substrate below the effective resonant region of the device; the air-gap type achieves contact between air and the lower side of the sandwich resonant structure by forming an air cavity at the substrate interface in the resonant region using sacrificial layer technology; and the solid-state assembled type achieves the reflection of acoustic waves from the lower side of the sandwich structure by adding a Bragg mirror structure between the substrate and the sandwich structure.

[0004] Traditional FBARs have a high temperature coefficient of frequency, such as -25 ppm / ℃ for traditional aluminum nitride piezoelectric thin film bulk acoustic resonators, causing their resonant performance to fluctuate significantly with ambient temperature. Over a wide operating temperature range (e.g., -50 ~ 85℃), this temperature dependence degrades filter performance, thus limiting its applications.

[0005] Patent application CN104242864A discloses a FBAR and filter with temperature compensation and resonant frequency tuning functions. The FBAR includes a substrate, a temperature compensation and resonant frequency tuning layer, a support layer, a bottom electrode, a top electrode, and a piezoelectric thin film. A groove is provided in the middle of the bottom of the temperature compensation and resonant frequency tuning layer, and the substrate is disposed below the two sides of the groove, forming a cavity between the substrate and the bottom surface of the temperature compensation and resonant frequency tuning layer. The support layer is disposed on top of the temperature compensation and resonant frequency tuning layer. A piezoelectric thin film is disposed between the bottom electrode and the top electrode. This FBAR and filter can effectively reduce the temperature-frequency drift caused by the negative temperature coefficient piezoelectric thin film, thereby improving the temperature stability of the FBAR. In the post-processing, by controlling the etching time of the temperature compensation and resonant frequency tuning layer in the FBAR stack to adjust its thickness, the frequency drift caused by process errors can be effectively reduced, thereby improving the frequency accuracy of the FBAR. However, the prior art only adjusts the frequency offset and temperature compensation by controlling the thickness of the temperature compensation layer through back etching. It requires continuous adjustment of the etching temperature compensation layer thickness through feedback to meet the design requirements. The feedback mechanism is complex to implement and its accuracy is limited by the process (it cannot control the temperature of the FBAR), thus it cannot achieve precise control of the frequency offset.

[0006] Utility model CN207939485U discloses a novel frequency-tunable thin-film bulk acoustic resonator, comprising a substrate, a temperature compensation layer, an adjustment layer, an isolation layer, and a piezoelectric stack layer. The piezoelectric stack layer includes a lower electrode, a piezoelectric thin film, and an upper electrode. The temperature compensation layer material has a positive temperature coefficient, which can effectively reduce the temperature-frequency drift caused by the negative temperature coefficient piezoelectric thin film and improve the stability of the thin-film bulk acoustic resonator. Simultaneously, the temperature compensation layer material needs to have low thermal conductivity to isolate the temperature, ensuring that the heat transferred from the heat source is mainly concentrated in the piezoelectric stack layer, thus improving the heating efficiency of the piezoelectric stack layer. The adjustment layer is made of metal. An external heat source heats the adjustment layer, causing a change in the temperature of the piezoelectric stack layer, which in turn changes the Young's modulus and frequency. Based on this principle, temperature adjustment achieves frequency regulation of the thin-film bulk acoustic resonator. The isolation layer separates the adjustment layer and the piezoelectric stack layer, supports the main structure of the thin-film bulk acoustic resonator, and also provides acoustic wave confinement. However, the prior art only heats the metal conditioning layer through an external heat source, which cannot accurately control and feedback the actual temperature of the device area, and therefore cannot truly achieve precise control of frequency offset. In the micro-hot plate structure used in this invention, the heating electrode and the measuring electrode work together in the external circuit system. The real-time feedback of the device temperature by the measuring electrode is used to adjust the heating electrode for electric heating or heat conduction, thereby precisely controlling the temperature within the effective area of ​​the device. Combined with the temperature compensation of the isolation layer structure, precise frequency regulation is achieved. Summary of the Invention

[0007] This invention provides a low-power temperature-compensated and temperature-controlled bulk acoustic wave resonator (FBAR). This FBAR achieves low-power temperature compensation and operating temperature control, so that the operating temperature of the FBAR device is not affected by the external temperature. Through temperature compensation and operating temperature control, precise control of frequency offset is achieved.

[0008] This invention provides a temperature-compensated and temperature-controlled bulk acoustic wave resonator, comprising a substrate, a resonant structure, and at least one micro-hot plate structure; Wherein, the resonant structure is vertically adjacent to at least one micro-hot plate structure, the substrate is vertically adjacent to the resonant structure, or the substrate is vertically adjacent to the micro-hot plate structure. The micro-hot plate structure is used to provide temperature compensation, temperature regulation, and temperature measurement, thereby enabling precise control of device frequency offset.

[0009] Preferably, the substrate, the micro-hot plate structure, and the resonant structure are stacked sequentially from bottom to top.

[0010] Preferably, the micro-thermal structure is located above the resonant structure. When the micro-thermal structure is located above the resonant structure, the heat dissipation effect of the metal electrode is better, and the downward adjustment of the device temperature is more sensitive.

[0011] When the micro-thermal structure is located below the resonant structure, the downward thermal conduction of the device to the substrate is blocked by the isolation layer, which is more conducive to the heating of the device and the upward adjustment of the device temperature.

[0012] Preferably, the micro-hot plate structure includes an isolation layer and heating electrodes and measuring electrodes located inside the isolation layer; The isolation layer is made of a temperature-compensating material, and the isolation layer is used to achieve temperature compensation. The heating electrode is used to regulate the temperature, and the measuring electrode is used to measure the temperature.

[0013] This invention utilizes an external device to connect a heating electrode and a measuring electrode. Based on the measured temperature signal transmitted by the measuring electrode, the heating electrode is regulated by the external device. The heat transmitted by the heating electrode is used to regulate the operating temperature of the FBAR. This invention enables low-power temperature control by utilizing the heating electrode and the measuring electrode.

[0014] More preferably, the heating electrode and the measuring electrode are arranged in a coplanar or non-coplanar configuration. A non-coplanar configuration allows for better selection of materials and shapes for both the heating and measuring electrodes; a coplanar configuration further simplifies the process steps and reduces its complexity. Furthermore, when the heating and measuring electrodes are located on the same plane, they can be combined into a single electrode, which simultaneously performs both heating and measuring functions, thereby further simplifying the process.

[0015] More preferably, the material of the heating electrode is a metallic material such as molybdenum, copper, platinum, tungsten, aluminum, silver, or gold, and the material of the heating electrode is a heatable metallic material.

[0016] More preferably, the measuring electrode is made of platinum. This metallic material is commonly used in the fabrication of thermal resistance materials for thermistors and has a linear temperature coefficient (TCR).

[0017] More preferably, the heating electrode is used for temperature control, and its shape and electrode thickness can be adjusted according to the device structure shape and the device usage scenario; The measuring electrode is used for temperature detection, and its shape and electrode thickness can be adjusted according to the device structure and usage scenario.

[0018] More preferably, the isolation layer is used for isolation and may also be made of a temperature-compensating material to enhance its temperature compensation effect. Its shape and thickness can be adjusted according to the specific temperature compensation and isolation requirements of the device.

[0019] Preferably, the substrate, resonant structure, and micro-hotplate structure are stacked sequentially from bottom to top. In this configuration, the micro-hotplate structure is located above the resonant structure, allowing heat conduction through the substrate below the resonant structure, while the metal electrodes of the micro-hotplate structure above can also assist in heat dissipation, facilitating downward temperature regulation.

[0020] Preferably, the substrate, one micro-hotplate structure, the resonant structure, and another micro-hotplate structure are stacked sequentially from bottom to top. The use of dual micro-hotplate structures in this configuration results in a more uniform temperature distribution along the z-axis of the device.

[0021] Preferably, the micro-hot plate structure located on the resonant structure includes an isolation layer, a heating electrode, and a measuring electrode; The heating electrode and the measuring electrode are located inside or above the isolation layer, or one of the heating electrode and the measuring electrode is located inside the isolation layer and the other is located above the isolation layer; The isolation layer is made of a temperature-compensating material, and the isolation layer is used to achieve temperature compensation. The heating electrode is used to regulate the temperature, and the measuring electrode is used to measure the temperature. The heating electrode and the measuring electrode may be arranged in a coplanar manner or not.

[0022] When the micro-thermal structure is located on top, the exposure of the heating and measuring electrodes can help dissipate heat better, thereby reducing the temperature and achieving downward temperature regulation.

[0023] Preferably, the resonant structure includes a lower electrode, a piezoelectric layer, and an upper electrode stacked from bottom to top; The substrate includes a cavity substrate, a back-etched substrate, and a solid-state assembly substrate with a Bragg reflector layer.

[0024] More preferably, the Bragg reflector layer is an acoustic wave reflection structure composed of high and low acoustic impedance materials, used in solid-state assembled BAW.

[0025] On the other hand, the present invention also provides a method for preparing the temperature-compensated and temperature-controlled bulk acoustic resonator according to the above, comprising: A resonant structure is formed on the substrate, and a micro-hot plate structure is formed on the resonant structure. Alternatively, a micro-hotplate structure can be formed on the substrate, and a resonant structure can be formed on the micro-hotplate structure. Alternatively, a micro-hotplate structure can be formed on the substrate, a resonant structure can be formed on the micro-hotplate structure, and another micro-hotplate structure can be formed on the resonant structure.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes at least one micro-hot plate structure placed at the upper and lower adjacent positions of the resonant structure to achieve temperature compensation. While controlling the temperature compensation coefficient, it also controls the operating temperature of the FBAR, preventing external interference to the FBAR operating temperature and expanding its application scenarios. Because this invention can simultaneously control the temperature compensation coefficient and the operating temperature, it enhances the temperature control effect, thereby enabling precise adjustment of frequency offset and achieving more accurate temperature regulation to a more ideal operating frequency band. Attached Figure Description

[0027] Figure 1 Three cross-sectional views of a temperature-compensated and temperature-controlled bulk acoustic resonator provided in specific embodiments of the present invention are shown. Figure 1 (a) is a resonator with a lower micro-hot plate structure. Figure 1 (b) is a resonator with a micro-hot plate structure. Figure 1 (c) is a resonator with upper and lower dual micro-thermal structures, wherein the substrate is 100, the lower micro-thermal plate structure is 109A, the upper micro-thermal plate structure is 109B, the resonant structure is 110, the lower electrode is 106, the piezoelectric layer is 107, and the upper electrode is 108.

[0028] Figure 2 Three cross-sectional views of the substrate provided in specific embodiments of the present invention are shown, wherein, Figure 2 (a) is a cavity-type substrate. Figure 2 (b) is a back-etched substrate. Figure 2 (c) is a solid-state assembled substrate with a Bragg reflector layer.

[0029] Figure 3 This is a cross-sectional view of the lower micro-hot plate structure provided in a specific embodiment of the present invention, wherein, Figure 3 (a) is a cross-sectional view of the lower micro-hotplate structure with a non-coplanar dual-electrode structure. Figure 3(b) is a cross-sectional view of the micro-hot plate structure under the dual-electrode coplanar structure, wherein the isolation layer is 103, the heating electrode is 104, and the measuring electrode is 105.

[0030] Figure 4 This is a cross-sectional view of the upper micro-hot plate structure provided in a specific embodiment of the present invention, wherein, Figure 4 (a) is a cross-sectional view of the upper micro-hot plate structure with a non-coplanar dual-electrode structure. Figure 4 (b) is a cross-sectional view of the upper micro-hot plate structure with a coplanar dual-electrode structure. Figure 4 (c) is a cross-sectional view of the upper micro-hot plate structure with exposed electrodes and a non-coplanar dual-electrode structure. Figure 4 (d) is a cross-sectional view of the upper micro-hot plate structure with exposed electrodes and a coplanar dual-electrode structure, wherein the isolation layer is 103, the heating electrode is 104, and the measuring electrode is 105.

[0031] Figure 5 This is a cross-sectional view of the micro-thermal resonator provided in a specific embodiment of the present invention. Figure 5 (a) is a cross-sectional view of the lower micro-thermal structure resonator, which is a dual-electrode non-coplanar structure. Figure 5 (b) is a cross-sectional view of the lower micro-thermal structure resonator, which is a dual-electrode coplanar structure.

[0032] Figure 6 This is a cross-sectional view of the upper micro-thermal structure resonator provided in a specific embodiment of the present invention. Figure 6 (a) is a cross-sectional view of the upper micro-thermal structure resonator with a non-coplanar dual-electrode structure. Figure 6 (b) is a cross-sectional view of the upper micro-thermal structure resonator with a coplanar dual-electrode structure. Figure 6 (c) is a cross-sectional view of a micro-thermal resonator with exposed electrodes and a non-coplanar dual-electrode structure. Figure 6 (d) is a cross-sectional view of the micro-thermal structure resonator with exposed electrodes and a coplanar dual-electrode structure.

[0033] Figure 7 This is a cross-sectional view of the upper and lower dual micro-thermal structure resonator provided in a specific embodiment of the present invention.

[0034] Figure 8 This is a cross-sectional view of the CMP filling of the sacrificial layer provided in a specific embodiment of the present invention. The cavity 101 is filled with the sacrificial layer, which can be ZnO. Dilute hydrochloric acid is used to release the ZnO of the sacrificial layer to protect the SiO2 material used in other layers.

[0035] Figure 9 This is a cross-sectional view of the deposition of the isolation layer 103 in a specific embodiment of the present invention.

[0036] Figure 10A cross-sectional view of the deposition heating electrode 104 and the measurement electrode 105 provided in a specific embodiment of the present invention, after being patterned.

[0037] Figure 11 This is a cross-sectional view of the deposited isolation layer 103 after CMP, provided in a specific embodiment of the present invention.

[0038] Figure 12 This is a cross-sectional view of a specific embodiment of the present invention after depositing a resonant structure including a lower electrode 106, a piezoelectric layer 107, and an upper electrode 108.

[0039] Figure 13 This is a cross-sectional view of the deposition isolation layer 103 provided in a specific embodiment of the present invention.

[0040] Figure 14 A cross-sectional view of the deposition heating electrode 104 and the measurement electrode 105 provided in a specific embodiment of the present invention, after being patterned.

[0041] Figure 15 This is a cross-sectional view of the through-hole after etching and releasing the sacrificial layer, provided for a specific embodiment of the present invention.

[0042] Figure 16 The admittance curves and placement diagrams provided for specific embodiments of the present invention, wherein, Figure 16 (a) is the admittance curve obtained from the simulation. Figure 16 (b) is a graph of fs versus temperature obtained from the simulation. Detailed Implementation

[0043] The following detailed description is provided with specific implementation examples. These examples are only relevant parts of the invention and are intended to help those skilled in the art understand the principles of the invention; they do not constitute any limitation on the invention. It should be noted that corresponding structural adjustments and changes can be made based on the concept of this invention, and all such modifications and changes fall within the scope of protection of this invention.

[0044] The purpose of this invention is to provide a low-power temperature-compensated and temperature-controlled bulk acoustic wave (SAW) resonator structure and fabrication method. The basic structure includes a substrate, a sandwich resonator structure, and a temperature-compensated and temperature-controlled structure (micro-hotplate). Compared to traditional SAW resonators that simply insert a temperature compensation layer, this invention introduces a temperature-compensated and temperature-controlled structure (micro-hotplate) composed of heating electrodes, an isolation layer, and measuring electrodes into the SAW resonator. This structure enables temperature compensation and low-power temperature control. On the one hand, it improves the temperature stability of the device during operation, expanding its application scenarios; on the other hand, it allows for stable operation within the corresponding target frequency band by actively controlling the temperature.

[0045] The invention will be further illustrated below with specific examples. For instance... Figure 1As shown, specific embodiments of the present invention provide three structures: a lower micro-hot plate resonator, an upper micro-hot plate resonator, and a dual upper and lower micro-hot plate resonator. like Figure 1 As shown in (a), the lower micro-thermal structure resonator provided in a specific embodiment of the present invention includes a substrate 100, a lower micro-thermal plate structure 109A and a resonant structure 110 stacked sequentially from bottom to top.

[0046] The resonant structure 110 provided in a specific embodiment of the present invention includes a lower electrode 106, a piezoelectric layer 107 and an upper electrode 108 stacked sequentially from bottom to top, wherein the lower electrode 106 is located on the lower micro-hot plate structure 109A.

[0047] like Figure 1 As shown in (b), the lower micro-thermal structure resonator provided in a specific embodiment of the present invention includes a substrate 100, a resonant structure 110 and an upper micro-thermal plate structure 109B stacked sequentially from bottom to top.

[0048] The resonant structure 110 provided in a specific embodiment of the present invention includes a lower electrode 106, a piezoelectric layer 107 and an upper electrode 108 stacked sequentially from bottom to top. The lower electrode 106 is located on the substrate 100 and the upper electrode 108 is located at the bottom of the upper micro-hot plate structure 109B.

[0049] like Figure 1 As shown in (c), the lower micro-thermal structure resonator provided in a specific embodiment of the present invention includes a substrate 100, a lower micro-thermal plate structure 109A, a resonant structure 110 and an upper micro-thermal plate structure 109B stacked sequentially from bottom to top.

[0050] The resonant structure 110 provided in a specific embodiment of the present invention includes a lower electrode 106, a piezoelectric layer 107 and an upper electrode 108 stacked sequentially from bottom to top. The lower electrode 106 is located on the upper micro-hot plate structure 109B and the upper electrode 108 is located at the bottom of the lower micro-hot plate structure 109A.

[0051] like Figure 2 (a)- Figure 2 As shown in (c), the substrates provided in specific embodiments of the present invention include cavity substrates made using sacrificial layer technology, back-etched substrates made by etching the substrate, and solid-state assembly substrates with Bragg reflective layers prepared by thin film deposition.

[0052] like Figure 3 As shown, the lower micro-hotplate structure provided in the specific embodiments of the present invention includes a lower micro-hotplate structure with a non-coplanar dual-electrode structure and a lower micro-hotplate structure with a coplanar dual-electrode structure.

[0053] like Figure 3As shown in (a), the lower micro-hot plate structure provided in this embodiment includes an isolation layer 103 and a heating electrode 104 and a measuring electrode 105 located inside the isolation layer. The heating electrode 104 and the measuring electrode 105 are located on different planes. At this time, the material and shape of the two electrodes are not restricted by each other, and the dual electrodes can be designed with more refined materials and shapes respectively.

[0054] like Figure 3 As shown in (b), the lower micro-hot plate structure provided in this embodiment includes an isolation layer 103 and a heating electrode 104 and a measuring electrode 105 located inside the isolation layer. The heating electrode 104 and the measuring electrode 105 are located on the same plane, making the process more streamlined. Furthermore, when the heating electrode and the measuring electrode are located on the same plane, they can be combined into one electrode, which has both heating and measuring functions, thereby further simplifying the process.

[0055] like Figure 4 As shown, the upper micro-hot plate structure provided in the specific embodiments of the present invention includes a lower micro-hot plate structure with two non-coplanar electrodes, a lower micro-hot plate structure with two coplanar electrodes, a lower micro-hot plate structure with exposed electrodes and two non-coplanar electrodes, or a lower micro-hot plate structure with exposed electrodes and two coplanar electrodes.

[0056] like Figure 4 As shown in (a), the upper micro-hot plate structure provided in this embodiment includes an isolation layer 103 and a heating electrode 104 and a measuring electrode 105 located inside the isolation layer. The heating electrode 104 and the measuring electrode 105 are located on different planes. At this time, the material and shape of the two electrodes are not restricted by each other, and the dual electrodes can be designed with more refined materials and shapes respectively.

[0057] like Figure 4 As shown in (b), the upper micro-hot plate structure provided in this embodiment includes an isolation layer 103 and a heating electrode 104 and a measuring electrode 105 located inside the isolation layer. The heating electrode 104 and the measuring electrode 105 are located on the same plane, making the process more streamlined. Furthermore, when the heating electrode and the measuring electrode are located on the same plane, they can be combined into one electrode, which has both heating and measuring functions, thereby further simplifying the process.

[0058] like Figure 4As shown in (c), the upper micro-hot plate structure provided in this embodiment includes an isolation layer 103 and a heating electrode 104 and a measuring electrode 105 located inside the isolation layer. The heating electrode 104 is located on the isolation layer 103, and the measuring electrode 105 is located inside the isolation layer, forming different planes. The heating electrode 104 is exposed, so the material and shape of the two electrodes are not constrained by each other, allowing for more refined design of the material and shape of the two electrodes. At the same time, the exposure of the heating electrode can assist in better heat dissipation, thereby reducing the temperature and achieving downward temperature regulation.

[0059] like Figure 4 As shown in (d), the upper micro-hot plate structure provided in this embodiment includes an isolation layer 103 and a heating electrode 104 and a measuring electrode 105 located inside the isolation layer. Both the heating electrode 104 and the measuring electrode 105 are located on the isolation layer 103, on the same plane, and are exposed. In this case, the material and shape of each electrode are not constrained by the other, allowing for more refined design of the material and shape for each electrode. Simultaneously, the exposure of the heating electrode and the measuring electrode assists in better heat dissipation, thereby reducing the temperature and achieving downward temperature regulation.

[0060] like Figure 5 As shown, specific embodiments of the present invention provide Figure 1 (a) shows the specific structure of the lower micro-hot plate resonator, as follows: Figure 5 As shown in (a), the substrate is a cavity type substrate, and the lower micro-hotplate structure is a dual-electrode non-coplanar lower micro-hotplate structure; as Figure 5 As shown in (b), the substrate is a cavity type substrate, and the lower micro-hot plate structure is a lower micro-hot plate structure with a dual-electrode coplanar structure.

[0061] like Figure 6 As shown, specific embodiments of the present invention provide Figure 1 (b) shows the specific structure of the upper micro-hot plate resonator, as follows: Figure 6 As shown in (a), the substrate is a cavity type substrate, and the upper micro-hotplate structure is a dual-electrode non-coplanar upper micro-hotplate structure; as Figure 6 As shown in (b), the substrate is a cavity type substrate, and the upper micro-hotplate structure is a dual-electrode coplanar upper micro-hotplate structure; as Figure 6 As shown in (c), the substrate is a cavity type substrate, and the upper micro-hotplate structure is an exposed dual-electrode non-coplanar upper micro-hotplate structure; as Figure 6 As shown in (d), the substrate is a cavity type substrate, and the upper micro-hot plate structure is an upper micro-hot plate structure with exposed electrodes and a coplanar dual-electrode structure.

[0062] like Figure 7 As shown, specific embodiments of the present invention provide Figure 1(c) shows the specific structure of the upper and lower double micro-hot plate resonator. The substrate is a cavity substrate. The lower micro-hot plate structure adopts a double-electrode coplanar structure, and the upper micro-hot plate structure adopts an exposed electrode double-electrode coplanar structure. The coplanar structure simplifies the complexity of the process implementation. The upper and lower double micro-hot plate structure takes into account the temperature uniformity in the thickness direction. The exposed electrode of the upper micro-hot plate can assist in better heat dissipation and also simplify the electrode manufacturing process.

[0063] On the other hand, the present invention also provides a method for fabricating a temperature-compensated and temperature-controlled bulk acoustic resonator, comprising: (1) Clean the substrate 100 by ultrasonic water washing with acetone and isopropanol. The crystal orientation of the silicon substrate can be any one of (110), (111) or (100).

[0064] (2) After cavity pattern photolithography, ICP etching process is used to etch a pattern with a depth of about 4 μm and an area of ​​0.25~50 kμm on the silicon substrate. 2 Cavity 101.

[0065] (3) Based on step (2), a ZnO thin film is deposited on the silicon surface by magnetron sputtering as a sacrificial layer material for the cavity. Then, chemical mechanical polishing (CMP) is used to remove the surface sacrificial layer material and level the material inside and outside the cavity. The structure obtained after CMP is as follows: Figure 8 As shown.

[0066] (4) A 50-800 nm thick silicon oxide isolation layer 103 is deposited on the silicon substrate and the surface of the sacrificial layer in the cavity using methods such as chemical vapor deposition or magnetron sputtering. The device structure after deposition is as follows: Figure 9 As shown.

[0067] (5) A heating electrode 104 and a measuring electrode 105 of 50-500 nm are deposited and etched on the isolation layer. The patterned device structure is as follows: Figure 10 As shown.

[0068] (6) Deposit 50-800nm ​​silicon oxide as an isolation layer 103 above the electrode, and perform CMP on the isolation layer until it is flat, such as... Figure 11 As shown.

[0069] (7) Based on step 6, sequentially deposit the lower electrode Mo using magnetron sputtering or thermal evaporation followed by photolithography and etching, deposit the piezoelectric AlN layer, and deposit the upper electrode Mo followed by photolithography and etching, such as Figure 12 As shown.

[0070] (8) Deposit silicon oxide as an isolation layer on the upper electrode, such as Figure 13 As shown.

[0071] (9) Deposit heating electrode and measuring electrode materials on the isolation layer, perform dry etching after photolithography to pattern them, and then wash away the residual photoresist, such as... Figure 14 As shown.

[0072] (10) The through-hole pattern is photolithographically patterned, then the through-holes and release holes are dry etched, and finally the sacrificial ZnO layer is released using dilute hydrochloric acid, such as... Figure 15 As shown.

[0073] The substrate material can be one of silicon, glass, silicon carbide, ceramic, silicon oxide, or any combination thereof, without specific limitations. The cavity 101 can be formed by wet etching or dry etching. The cross-sectional shape of the cavity 101 can be any one of trapezoidal, triangular, rectangular, or a combination thereof. The depth of the cavity can be 2-8 μm, and the lateral width depends on the requirements of the device design, but is not less than the lateral dimension of the upper electrode 108.

[0074] The isolation layer 103 can be silicon oxide, silicon nitride, or silicon carbide, and its thickness is no greater than that of the resonator. Both can provide frequency temperature coefficient compensation. The isolation layer can provide mechanical support and isolate the electrodes.

[0075] The heating electrode 104 and the measuring electrode 105 can be any one or a combination of metals such as molybdenum, copper, platinum, tungsten, aluminum, silver, and gold, with a thickness of 50nm-1000nm, depending on the actual design requirements of the device. The metal is patterned using methods such as wet etching and plasma etching to obtain the pattern required by the design.

[0076] The piezoelectric layer 107 can be a piezoelectric material such as aluminum nitride, scandium-doped aluminum nitride, zinc oxide, lithium niobate, or lead zirconate titanate, and has good roughness.

[0077] The materials of the lower electrode 106 and the upper electrode 108 can be any one or a combination of several metals such as molybdenum, copper, platinum, tungsten, aluminum, silver, and gold, with a thickness of 50nm-1000nm, determined according to the actual design requirements of the device. The metal is patterned using methods such as wet etching and plasma etching to obtain the pattern required by the design.

[0078] The sacrificial layer material can be zinc oxide, which can be released using dilute hydrochloric acid. As a sacrificial layer, zinc oxide can protect the structure composed of silicon oxide material from corrosion when the sacrificial layer is released.

[0079] The thin-film bulk acoustic resonator in the above examples can be a cavity-type FBAR, that is, the cavity 101 is formed by releasing the sacrificial layer to form a cavity, or the thin-film bulk acoustic resonator can also be a Bragg reflector-structured FABR, that is, a solid-state assembled FABR, or a back-etched FABR. That is, the above examples do not limit the present invention.

[0080] like Figure 16 ,Depend on Figure 16 The admittance curves of the device in (a) at different temperatures were obtained. Figure 16 (b) shows the relationship between fs and temperature T. When the device's fs needs to operate at a specific value, such as 1.616 GHz, the operating temperature can be controlled at 329 K (approximately 55.85 °C) by adding a micro-hot plate structure. The isolation layer 103 can control the slope of the straight line in graph b through temperature compensation, and the heating electrode 104 and measuring electrode 105 work together to precisely control the temperature.

Claims

1. A temperature-compensated and temperature-controlled bulk acoustic resonator, characterized in that, Includes a substrate, a resonant structure, and at least one micro-hot plate structure; Wherein, the resonant structure is vertically adjacent to at least one micro-hot plate structure, the substrate is vertically adjacent to the resonant structure, or the substrate is vertically adjacent to the micro-hot plate structure. The micro-hot plate structure is used to provide temperature compensation, temperature regulation, and temperature measurement, thereby enabling control of device frequency offset.

2. The temperature-compensated and temperature-controlled bulk acoustic resonator according to claim 1, characterized in that, The substrate, the micro-hot plate structure, and the resonant structure are stacked sequentially from bottom to top.

3. The temperature-compensated and temperature-controlled bulk acoustic resonator according to claim 1, characterized in that, The micro hot plate structure includes an isolation layer and heating and measuring electrodes located inside the isolation layer; The isolation layer is made of a temperature-compensating material, and the isolation layer is used to achieve temperature compensation. The heating electrode is used to regulate the temperature, and the measuring electrode is used to measure the temperature.

4. The temperature-compensated and temperature-controlled bulk acoustic resonator according to claim 3, characterized in that, The heating electrode and the measuring electrode may be arranged in a coplanar manner or not.

5. The low-power temperature-compensated and temperature-controlled bulk acoustic resonator according to claim 1, characterized in that, The substrate, resonant structure, and micro-hot plate structure are stacked sequentially from bottom to top.

6. The temperature-compensated and temperature-controlled bulk acoustic resonator according to claim 1, characterized in that, The substrate, a micro-hotplate structure, a resonant structure, and another micro-hotplate structure are stacked sequentially from bottom to top.

7. The temperature-compensated and temperature-controlled bulk acoustic resonator according to claim 5 or 6, characterized in that, The micro-hot plate structure located on the resonant structure includes an isolation layer, a heating electrode, and a measuring electrode; The heating electrode and the measuring electrode are located inside or above the isolation layer, or one of the heating electrode and the measuring electrode is located inside the isolation layer and the other is located above the isolation layer; The isolation layer is made of a temperature-compensating material, and the isolation layer is used to achieve temperature compensation. The heating electrode is used to regulate the temperature, and the measuring electrode is used to measure the temperature. The heating electrode and the measuring electrode may be arranged in a coplanar manner or not.

8. The low-power temperature-compensated and temperature-controlled bulk acoustic resonator according to claim 1, characterized in that, The resonant structure includes a lower electrode, a piezoelectric layer, and an upper electrode stacked from bottom to top; The substrate includes a cavity substrate, a back-etched substrate, and a solid-state assembly substrate with a Bragg reflector layer.

9. A method for fabricating a temperature-compensated and temperature-controlled bulk acoustic resonator according to any one of claims 1-8, characterized in that, include: A resonant structure is formed on the substrate, and a micro-hot plate structure is formed on the resonant structure. Alternatively, a micro-hotplate structure can be formed on the substrate, and a resonant structure can be formed on the micro-hotplate structure. Alternatively, a micro-hotplate structure can be formed on the substrate, a resonant structure can be formed on the micro-hotplate structure, and another micro-hotplate structure can be formed on the resonant structure.

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