Film bulk acoustic resonator structure with dual stress adjustment and preparation method thereof

Abstract

The invention discloses a film bulk acoustic resonator structure with dual stress regulation and a preparation method thereof. The film bulk acoustic resonator structure comprises a resonant structure and a capacitive stress regulation structure. The capacitive stress regulation and control structure comprises a first stress regulation and control structure and a second stress regulation and control structure; the first stress regulation and control structure and the second stress regulation and control structure are parallel plate capacitive structures; the resonance structure is located between the first stress regulation and control structure and the second stress regulation and control structure. According to the invention, the first top electrode in the first stress loading structure and the third bottom electrode in the second stress loading structure are driven by electrostatic force, so that the elastic rigidity coefficient of the piezoelectric layer is changed, the resonant frequency of the resonator is further changed, and temperature compensation is realized. Meanwhile, modulation signals and excitation signals can be effectively separated, and the device has the advantages of being small in size, low in cost and low in power consumption. The preparation method is simple and can be used for large-scale preparation.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency communication, and in particular to a thin film bulk acoustic wave resonator structure and a preparation method thereof. Background Art

[0002] With the continuous development of communication technology and the continuous increase in communication frequency bands, RF terminals have put forward higher performance and smaller size requirements for RF filters. Film Bulk Acoustic Resonator (FBAR) has the advantages of high resonant frequency, high quality factor, and small size. The filter prepared by it has excellent performance and has gradually become one of the hot spots in RF filter research.

[0003] The main structure of FBAR is a sandwich structure consisting of an upper metal electrode-piezoelectric film-lower metal electrode. When a radio frequency signal is applied to the upper and lower electrodes of FBAR, a longitudinal wave propagating in the thickness direction is excited in the piezoelectric film and reflected at the upper and lower interfaces of the sandwich structure. When the longitudinal wave meets the conditions of standing wave oscillation in the sandwich structure, the acoustic wave loss is minimal. Then, the piezoelectric film converts the longitudinal wave into an electrical signal through the piezoelectric effect, realizing the frequency selection function of the electrical signal. Near the frequency that makes the body longitudinal wave oscillate into a standing wave, if the phase of the electrical signal is consistent with the polarization phase of the piezoelectric film material, the FBAR produces series resonance with the minimum impedance, and the resonant frequency at this time is the series resonance frequency; if the phase of the electrical signal is opposite to the polarization phase of the piezoelectric film material, the FBAR produces parallel resonance with the maximum impedance, and the resonant frequency at this time is the parallel resonance frequency. The relative frequency spacing between the two is usually represented by the effective electromechanical coupling coefficient. The larger the relative spacing, the larger the effective electromechanical coupling coefficient.

[0004] In traditional FBAR devices, since piezoelectric materials and electrode materials have negative acoustic temperature coefficients, the series and parallel resonant frequencies of FBARs decrease as the temperature increases, which in turn causes the passband of the filter composed of FBARs to shift with temperature changes. If the passband of a filter used in a crowded frequency band shifts with temperature changes, it will be difficult to effectively filter out interference signals in adjacent frequency bands, causing device failure. Therefore, reducing the resonant frequency drift of FBAR caused by temperature is particularly important in FBAR filter applications.

[0005] In the prior art, there are mainly the following ways to compensate for the temperature drift of the FBAR resonant frequency: 1. By adding a temperature compensation layer with a positive sound velocity temperature coefficient to the FBAR structure, but the temperature compensation layer will cause the electromechanical coupling coefficient of the resonator to decrease, thereby causing the bandwidth of the FBAR filter to decrease. 2. By adding a heating device, such as a resistance wire, to the FBAR structure, the heat generated by the resistance wire causes the elastic stiffness coefficient of the piezoelectric material to change, thereby achieving temperature compensation. However, this method is more suitable for low temperature environments and has high power consumption. 3. By applying a DC bias to the upper and lower boundaries of the piezoelectric oscillator stack, the negative sound velocity temperature characteristics of the piezoelectric material are compensated, thereby achieving temperature compensation. However, since the DC bias signal is directly applied to the working electrode, there is a problem of mutual interference between the excitation signal and the DC bias signal, and the frequency adjustment range is small. 4. By connecting a voltage-controlled capacitor in series with the FBAR, the capacitance of the voltage-controlled capacitor is controlled by the voltage output by the bridge, and the voltage output by the bridge changes with temperature. Temperature compensation can be achieved through reasonable design. However, this method cannot simultaneously adjust the series and parallel resonant frequency of the FBAR. Therefore, it is necessary to propose a new type of temperature compensated thin film bulk acoustic wave resonator to solve the above problems. Summary of the invention

[0006] Purpose of the invention: In view of the above-mentioned prior art, a thin film bulk acoustic wave resonator structure with dual stress adjustment is proposed, which can simultaneously perform temperature compensation on the series and parallel resonant frequencies of FBAR without causing a significant decrease in the effective electromechanical coupling coefficient of FBAR. At the same time, a method with simple manufacturing process and large-scale preparation is proposed.

[0007] Technical solution: A thin film bulk acoustic wave resonator structure with dual stress regulation, comprising a resonant structure and a capacitive stress regulation structure; the capacitive stress regulation structure comprises a first stress regulation structure and a second stress regulation structure; the resonant structure is located between the first stress regulation structure and the second stress regulation structure; The first stress regulating structure comprises, from bottom to top, a first substrate, a first bottom electrode, a first cavity, a first insulating layer and a first top electrode; wherein the first cavity is located in the first insulating layer and is disposed between the first bottom electrode and the first top electrode; The second stress regulating structure comprises, from bottom to top, a third bottom electrode, a second cavity, a fourth insulating layer, a fifth insulating layer, a third top electrode and a second substrate; wherein the second cavity is located in the fourth insulating layer and the fifth insulating layer, and is disposed between the third bottom electrode and the third top electrode; The resonant structure comprises from bottom to top a second insulating layer, a second bottom electrode, a piezoelectric layer, a second top electrode and a third insulating layer; The overlapping area of ​​the first cavity, the first top electrode, the second insulating layer, the second bottom electrode, the piezoelectric layer, the second top electrode, the third insulating layer, the third bottom electrode and the second cavity in the thickness direction constitutes an effective resonance area of ​​the resonator.

[0008] Furthermore, the materials of the first top electrode, the second bottom electrode, the second top electrode and the third bottom electrode are conductive materials with a longitudinal wave characteristic acoustic impedance greater than 50 megohms; the first insulating layer, the second insulating layer, the third insulating layer, the fourth insulating layer and the fifth insulating layer are insulating materials with a longitudinal wave characteristic acoustic impedance less than 20 megohms.

[0009] Furthermore, the material of the first bottom electrode and the third top electrode is doped silicon, the material of the first top electrode, the second bottom electrode, the second top electrode and the third bottom electrode is tungsten or molybdenum, and the material of the first insulating layer, the second insulating layer, the third insulating layer, the fourth insulating layer and the fifth insulating layer is silicon dioxide.

[0010] Furthermore, the thicknesses of the first bottom electrode, the first insulating layer, the first top electrode, the second insulating layer, and the second bottom electrode satisfy a Bragg reflection condition, and the thicknesses of the second top electrode, the third insulating layer, the third bottom electrode, the fourth insulating layer, the fifth insulating layer, and the third top electrode satisfy a Bragg reflection condition.

[0011] Furthermore, the material of the piezoelectric layer is aluminum nitride, and its c-axis is oriented in the thickness direction.

[0012] Furthermore, the thickness of the first cavity and the second cavity is between 0.1 μm and 1 μm.

[0013] Furthermore, by applying a DC voltage signal to the first top electrode and the first bottom electrode in the first stress regulation structure and to the third bottom electrode and the third top electrode in the second stress regulation structure, a tensile stress is generated on the first top electrode in a direction toward the first bottom electrode, and a tensile stress is generated on the third bottom electrode in a direction toward the third top electrode, so that a tensile stress in the thickness direction is also generated in the piezoelectric layer, thereby offsetting the phenomenon that the elastic stiffness coefficient of the piezoelectric material decreases with increasing temperature, thereby achieving temperature compensation.

[0014] The method for preparing the thin film bulk acoustic wave resonator structure comprises: Step 1: performing ion implantation doping on the upper surface of the first substrate, and then performing high-temperature annealing on the first substrate to form a first bottom electrode; and then performing a magnetron sputtering process on the upper surface of the first bottom electrode to prepare a first insulating layer; Step 2: performing a photolithography process on the first insulating layer to etch out a first cavity sacrificial layer filling area, then performing a chemical vapor deposition process on the device surface to deposit a sacrificial layer material, and then removing excess sacrificial layer material through a chemical mechanical polishing process to form a first cavity sacrificial layer in the etched area in the first insulating layer; Step 3: depositing a first top electrode, a second insulating layer, a second bottom electrode, a piezoelectric layer, a second top electrode, a third insulating layer, a third bottom electrode and a fourth insulating layer in sequence on the first insulating layer and the first cavity sacrificial layer by a magnetron sputtering process; Step 4: etching a lower half region of the second cavity on the fourth insulating layer by a photolithography process; then releasing the first cavity sacrificial layer to form the first cavity; Step 5: performing ion implantation doping on the upper surface of the second substrate, and then performing high-temperature annealing on the second substrate to form a third top electrode; then performing a magnetron sputtering process on the upper surface of the third top electrode to prepare a fifth insulating layer, and performing a photolithography process to etch out an upper half region of the second cavity; Step 6: Turn over the second substrate, align the fifth insulating layer with the fourth insulating layer on the first substrate, and perform a bonding process to complete the preparation of the thin film bulk acoustic wave resonator.

[0015] Beneficial effects: 1. The present invention applies stress to the piezoelectric layer in the resonant structure through a capacitive stress loading structure to change the elastic stiffness coefficient of the piezoelectric material, thereby changing the longitudinal wave velocity of the piezoelectric material. Since the series and parallel resonant frequencies of the FBAR are positively correlated with the longitudinal wave velocity of the piezoelectric material, the effect of simultaneously adjusting the series and parallel resonant frequencies of the FBAR can be achieved.

[0016] 2. In the present invention, a DC bias signal is applied to the first bottom electrode and the first top electrode as well as the third bottom electrode and the third top electrode, and a radio frequency AC signal is applied to the second bottom electrode and the second top electrode. No additional bias device is required for signal superposition, thereby achieving effective separation of the modulation signal and the excitation signal.

[0017] 3. The stress loading method adopted by the present invention is to convert the DC bias electrical signal into electrostatic force. The leakage current generated by this method is extremely small, so the power consumption is very low.

[0018] 4. The present invention does not design an additional temperature compensation layer structure in the resonant structure, so while achieving temperature compensation, it will not cause a decrease in the effective electromechanical coupling coefficient of the FBAR. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a cross-sectional schematic diagram of the FBAR structure of the present invention; Figure 2-Figure 7 This is a schematic diagram of the FBAR structure process flow of the present invention; The reference numerals in the figure are: 1-first substrate; 2-first bottom electrode; 3-first insulating layer; 4-first cavity; 401-first cavity sacrificial layer; 5-first top electrode; 6-second insulating layer; 7-second bottom electrode; 8-piezoelectric layer; 9-second top electrode; 10-third insulating layer; 11-third bottom electrode; 12-fourth insulating layer; 13-fifth insulating layer; 14-second cavity; 1401-lower half area of ​​the second cavity; 1402-upper half area of ​​the second cavity; 15-third top electrode; 16-second substrate. DETAILED DESCRIPTION

[0020] The present invention will be further explained below in conjunction with the accompanying drawings.

[0021] like Figure 1 As shown, a thin film bulk acoustic wave resonator structure with dual stress regulation includes: a resonant structure and a capacitive stress regulation structure. The first stress regulation structure and the second stress regulation structure are both parallel plate capacitive structures, and the resonant structure is located between the first stress regulation structure and the second stress regulation structure.

[0022] The first stress regulating structure includes, from bottom to top, a first substrate 1, a first bottom electrode 2, a first cavity 4, a first insulating layer 3, and a first top electrode 5. The second stress regulating structure includes, from bottom to top, a third bottom electrode 11, a second cavity 14, a fourth insulating layer 12, a fifth insulating layer 13, a third top electrode 15, and a second substrate 16.

[0023] The resonant structure includes from bottom to top a second insulating layer 6, a second bottom electrode 7, a piezoelectric layer 8, a second top electrode 9 and a third insulating layer 10. Among them, the first cavity 4 is located in the first insulating layer 3 and is arranged between the first bottom electrode 2 and the first top electrode 5. The second cavity 14 is located in the fourth insulating layer 12 and the fifth insulating layer 13 and is arranged between the third bottom electrode 11 and the third top electrode 15. The overlapping area of ​​the first cavity 4, the first top electrode 5, the second insulating layer 6, the second bottom electrode 7, the piezoelectric layer 8, the second top electrode 9, the third insulating layer 10, the third bottom electrode 11 and the second cavity 14 in the thickness direction constitutes the effective resonant area of ​​the resonator. In order to facilitate bonding in the manufacturing process, in the structure, the single insulating layer is divided into a fourth insulating layer 12 and a fifth insulating layer 13; depending on the process, the fourth insulating layer 12 and the fifth insulating layer 13 can be fused into one insulating layer.

[0024] The material of the first substrate 1 and the second substrate 16 is single crystal silicon. The material of the first bottom electrode 2 and the third top electrode 15 is doped silicon. The material of the first top electrode 5, the second bottom electrode 7, the second top electrode 9 and the third bottom electrode 11 is a conductive material with a large acoustic impedance, such as metal materials such as tungsten (W) and molybdenum (Mo). The material of the first insulating layer 3, the second insulating layer 6, the third insulating layer 10, the fourth insulating layer 12 and the fifth insulating layer 13 is silicon dioxide. Since the acoustic impedance of the material of the electrode layer is large, while the acoustic impedance of the insulating layer is small, the thickness of the electrode layer and the insulating layer can be reasonably designed to form a Bragg reflection layer to reduce the energy of the leaked body acoustic wave in the resonant structure, thereby improving the quality factor of the resonator. The thickness of the electrode layer and the insulating layer is usually set to one-fourth of the wavelength of the body acoustic wave generated by the resonant structure.

[0025] The material of the piezoelectric layer 8 is aluminum nitride, and its c-axis is oriented in the thickness direction, so that its elastic stiffness coefficient is more obviously affected by tensile stress. The thickness of the first cavity 4 and the second cavity 14 will affect the magnitude of the electrostatic force in the first top electrode 5 and the third bottom electrode 11 respectively. Specifically, when the DC bias voltage applied between the first top electrode 5 and the first bottom electrode 2 is the same, the smaller the thickness of the first cavity 4, the greater the electrostatic force generated in the first top electrode 5, the greater the influence on the elastic stiffness coefficient of the piezoelectric layer 8, and the more obvious the effect of temperature compensation. Similarly, when the DC bias voltage applied between the third bottom electrode 11 and the third top electrode 15 is the same, the smaller the thickness of the second cavity 14, the greater the electrostatic force generated in the third bottom electrode 11, the greater the influence on the elastic stiffness coefficient of the piezoelectric layer 8, and the more obvious the effect of temperature compensation. However, if the thickness of the first cavity 4 or the second cavity 14 is too small, it is easy to cause the first top electrode 5 and the first bottom electrode 2 to be attracted, or the third top electrode 15 and the third bottom electrode 11 to be attracted, thereby causing the failure of the first stress loading structure or the second stress loading structure, and the resonant frequency of the FBAR cannot be adjusted, that is, the frequency compensation cannot be achieved. Therefore, the thickness of the first cavity 4 and the second cavity 14 is set between 0.1μm and 1μm, preferably 0.5μm.

[0026] The device structure of the present invention can achieve temperature compensation on the principle that a DC voltage signal is applied to the first top electrode and the first bottom electrode in the first stress regulating structure and the third bottom electrode and the third top electrode in the second stress regulating structure, so that a tensile stress in the direction of the first bottom electrode is generated on the first top electrode, and a tensile stress in the direction of the third top electrode is generated on the third bottom electrode, so that a tensile stress in the thickness direction is also generated in the piezoelectric layer. Since the elastic stiffness coefficient in the thickness direction of the piezoelectric material increases with the increase of the tensile stress, the phenomenon that the elastic stiffness coefficient of the piezoelectric material decreases with the increase of the temperature can be offset by applying tensile stress to the piezoelectric material, thereby achieving temperature compensation.

[0027] The method for preparing the above-mentioned thin film bulk acoustic wave resonator structure with dual stress regulation comprises the following steps: Step 1: If Figure 2 As shown in the figure, ion implantation is performed on the upper surface of the first substrate 1, and the implantation depth is 0.4μm~0.6μm. Then, the first substrate 1 is subjected to high-temperature annealing to activate the impurity ions and repair the lattice damage caused by the ion implantation, so as to form a first bottom electrode 2 on the upper surface of the first substrate 1. Subsequently, a magnetron sputtering process is performed on the upper surface of the first bottom electrode 2 to prepare a first insulating layer 3.

[0028] Step 2: If Figure 3 As shown, a photolithography process is performed on the first insulating layer 3 to etch out a first cavity sacrificial layer 401 filling area. Subsequently, a chemical vapor deposition process is performed on the device surface to deposit a sacrificial layer material BPSG, and then excess sacrificial layer material is removed by a chemical mechanical polishing process to form a first cavity sacrificial layer 401 in the etched area in the first insulating layer 3.

[0029] Step 3: If Figure 4 As shown, a first top electrode 5, a second insulating layer 6, a second bottom electrode 7, a piezoelectric layer 8, a second top electrode 9, a third insulating layer 10, a third bottom electrode 11 and a fourth insulating layer 12 are sequentially deposited on the first insulating layer 3 and the first cavity sacrificial layer 401 by a magnetron sputtering process, and a chemical mechanical polishing process is performed after each layer of thin film is deposited to improve the roughness of the film surface.

[0030] Step 4: Figure 5 As shown, the lower half region 1401 of the second cavity 14 is etched on the fourth insulating layer 12 by a photolithography process; then the first cavity sacrificial layer 401 is released to form the first cavity 4.

[0031] Step 5: Figure 6 As shown, a second substrate 16 is prepared, and ion implantation is performed on the upper surface of the second substrate 16, with an implantation depth of 0.4μm~0.6μm. Then, the second substrate 16 is subjected to high-temperature annealing to activate the impurity ions and repair the lattice damage caused by the ion implantation, and a third top electrode 15 is formed on the upper surface of the second substrate 16; then, a magnetron sputtering process is performed on the upper surface of the third top electrode 15 to prepare a fifth insulating layer 13, and patterning is performed to etch out the upper half area 1402 of the second cavity 14.

[0032] Step 6: Figure 7 As shown, the second substrate 16 is turned over, the fifth insulating layer 13 is aligned with the fourth insulating layer 12 on the first substrate 1, and a bonding process is performed to complete the preparation of the thin film bulk acoustic wave resonator.

[0033] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A thin film bulk acoustic wave resonator structure with dual stress regulation, characterized in that: Including a resonant structure and a capacitive stress regulating structure; The capacitive stress regulating structure includes a first stress regulating structure and a second stress regulating structure; The resonant structure is located between the first stress regulating structure and the second stress regulating structure; The first stress regulating structure comprises, from bottom to top, a first substrate (1), a first bottom electrode (2), a first cavity (4), a first insulating layer (3) and a first top electrode (5); wherein the first cavity (4) is located in the first insulating layer (3) and is arranged between the first bottom electrode (2) and the first top electrode (5); The second stress regulating structure comprises, from bottom to top, a third bottom electrode (11), a second cavity (14), a fourth insulating layer (12), a fifth insulating layer (13), a third top electrode (15), and a second substrate (16); wherein the second cavity (14) is located between the fourth insulating layer (12) and the fifth insulating layer (13), and is arranged between the third bottom electrode (11) and the third top electrode (15); The resonant structure comprises, from bottom to top, a second insulating layer (6), a second bottom electrode (7), a piezoelectric layer (8), a second top electrode (9) and a third insulating layer (10); The overlapping area of ​​the first cavity (4), the first top electrode (5), the second insulating layer (6), the second bottom electrode (7), the piezoelectric layer (8), the second top electrode (9), the third insulating layer (10), the third bottom electrode (11) and the second cavity (14) in the thickness direction constitutes an effective resonance area of ​​the resonator.

2. The thin film bulk acoustic wave resonator structure with dual stress regulation according to claim 1, characterized in that: The materials of the first top electrode (5), the second bottom electrode (7), the third top electrode (9) and the third bottom electrode (11) are conductive materials having a longitudinal wave characteristic acoustic impedance greater than 50 megaohms; The first insulating layer (3), the second insulating layer (6), the third insulating layer (10), the fourth insulating layer (12) and the fifth insulating layer (13) are made of insulating materials having a longitudinal wave characteristic acoustic impedance of less than 20 megaohms.

3. The thin film bulk acoustic wave resonator structure with dual stress regulation according to claim 2, characterized in that: The material of the first bottom electrode (2) and the third top electrode (15) is doped silicon, the material of the first top electrode (5), the second bottom electrode (7), the second top electrode (9) and the third bottom electrode (11) is tungsten or molybdenum, and the material of the first insulating layer (3), the second insulating layer (6), the third insulating layer (10), the fourth insulating layer (12) and the fifth insulating layer (13) is silicon dioxide.

4. The thin film bulk acoustic wave resonator structure with dual stress regulation according to claim 2 or 3, characterized in that: The thicknesses of the first bottom electrode (2), the first insulating layer (3), the first top electrode (5), the second insulating layer (6), and the second bottom electrode (7) satisfy a Bragg reflection condition, and the thicknesses of the second top electrode (9), the third insulating layer (10), the third bottom electrode (11), the fourth insulating layer (12), the fifth insulating layer (13), and the third top electrode (15) satisfy a Bragg reflection condition.

5. The thin film bulk acoustic wave resonator structure with dual stress regulation according to claim 4, characterized in that: The material of the piezoelectric layer (8) is aluminum nitride, and its c-axis is oriented in the thickness direction.

6. The thin film bulk acoustic wave resonator structure with dual stress regulation according to any one of claims 1-3 and 5, characterized in that: The thickness of the first cavity (4) and the second cavity (14) is between 0.1 μm and 1 μm.

7. The thin film bulk acoustic wave resonator structure with dual stress regulation according to any one of claims 1 to 3 and 5, characterized in that: By applying a DC voltage signal to the first top electrode (5) and the first bottom electrode (2) in the first stress regulation structure and to the third bottom electrode (11) and the third top electrode (15) in the second stress regulation structure, a tensile stress in a direction toward the first bottom electrode (2) is generated on the first top electrode (5), and a tensile stress in a direction toward the third top electrode (15) is generated on the third bottom electrode (11), so that a tensile stress in a thickness direction is also generated in the piezoelectric layer (8), thereby offsetting the phenomenon that the elastic stiffness coefficient of the piezoelectric material decreases with increasing temperature, thereby achieving temperature compensation.

8. The method for preparing a thin film bulk acoustic wave resonator structure according to any one of claims 1 to 7, characterized in that: include: Step 1: performing ion implantation doping on the upper surface of the first substrate (1), and then performing high-temperature annealing on the first substrate (1) to form a first bottom electrode (2); and then performing a magnetron sputtering process on the upper surface of the first bottom electrode (2) to prepare a first insulating layer (3); Step 2: performing a photolithography process on the first insulating layer (3) to etch out a first cavity sacrificial layer (401) filling area, then performing a chemical vapor deposition process on the device surface to deposit sacrificial layer material, and then removing excess sacrificial layer material through a chemical mechanical polishing process to form a first cavity sacrificial layer (401) in the etched area in the first insulating layer (3); Step 3: depositing a first top electrode (5), a second insulating layer (6), a second bottom electrode (7), a piezoelectric layer (8), a second top electrode (9), a third insulating layer (10), a third bottom electrode (11) and a fourth insulating layer (12) in sequence on the first insulating layer (3) and the first cavity sacrificial layer (401) by a magnetron sputtering process; Step 4: etching a lower half region (1401) of the second cavity (14) on the fourth insulating layer (12) by a photolithography process; then releasing the first cavity sacrificial layer (401) to form the first cavity (4); Step 5: performing ion implantation doping on the upper surface of the second substrate (16), and then performing high-temperature annealing on the second substrate (16) to form a third top electrode (15); then performing a magnetron sputtering process on the upper surface of the third top electrode (15) to prepare a fifth insulating layer (13), and performing a photolithography process to etch out an upper half region (1402) of the second cavity (14); Step 6: invert the second substrate (16), align the fifth insulating layer (13) with the fourth insulating layer (12) on the first substrate (1), and perform a bonding process to complete the preparation of the thin film bulk acoustic wave resonator.

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