Film Bulk Acoustic Resonator and Its Fabrication Process

Abstract

The present invention discloses a thin film bulk acoustic wave resonator and its manufacturing process. The manufacturing process includes: fabricating a substrate, etching a groove on the substrate and filling a release material in the groove; sequentially forming a lower electrode, a piezoelectric layer and an upper electrode on the substrate continuously to construct a piezoelectric thin film stack structure covering the release material; patterning the upper electrode and the piezoelectric layer so that the projections of the upper electrode and the piezoelectric layer in the direction perpendicular to the substrate are located within the edges of the groove; patterning the lower electrode, with a part of the lower electrode overlapping the substrate. The main purpose of the present invention is to improve the quality factor Q value of the thin film bulk acoustic wave resonator. Optimization is carried out from two aspects: the surface roughness of the film layer and the energy leakage at the interface of the thin film bulk acoustic wave resonator, avoiding the parasitic problems caused by electrode connection. It is proved by simulation that the Q value is indeed improved significantly.

Description

Technical Field

[0001] The present invention relates to the technical field of resonators, and more particularly to a thin film bulk acoustic wave resonator and a preparation process thereof. Background Art

[0002] With the development of mobile communication technology, the volume of mobile data transmission has also increased rapidly. Due to limited frequency resources, the transmission power of wireless power transmission equipment has become an issue that must be considered. At the same time, the requirements for the power of filters in the front-end circuits of mobile communication devices are also getting higher and higher. In recent years, the thin film bulk acoustic wave resonator (FBAR) developed based on semiconductor microfabrication technology has a higher working efficiency (1 - 10 GHz) compared to traditional surface acoustic wave (SAW) devices, quartz crystal resonators, and ceramic dielectric devices. In addition, the thin film bulk acoustic wave resonator has the advantages of small volume, high quality factor (Q value), and low loss. Therefore, the thin film bulk acoustic wave resonator has a very broad development and application prospect in wireless communication. Among them, the Q value is a key performance index of the thin film bulk acoustic wave resonator, which is used to judge the loss situation of sound waves. Summary of the Invention

[0003] The present invention is made based on the inventor's discovery and understanding of the following facts and problems:

[0004] The main factors affecting the quality factor Q value of the thin film bulk acoustic wave resonator are as follows: the quality of the thin film itself, which is mainly affected by the thin film material itself; the roughness of the thin film surface, and larger roughness on the surfaces of the electrode and the piezoelectric layer thin film will cause scattering loss of sound waves, resulting in a decrease in the Q value; the leakage of sound waves, the leakage of sound waves at the boundary of the thin film bulk acoustic wave resonator structure, or the leakage of sound waves to the non-resonant area when the resonator is connected, will also reduce the Q value of the resonator. Among them, most thin film bulk acoustic wave resonators currently select ALN as the piezoelectric material and Moly as the electrode material. Therefore, the present invention does not study the influence of the thin film material itself on the quality factor for the time being.

[0005] The inventor has found that since the thin film bulk acoustic wave resonator has multiple film layers, in the processing technology of the thin film bulk acoustic wave resonator in the related art, after the deposition of each film layer, processes such as gluing, photolithography, etching, and degluing are required. These multiple process steps will corrode the film layer surface to a certain extent, increase the roughness of the film layer surface, cause loss of sound wave energy, and reduce the Q value.

[0006] In addition, the inventor has also found that the overlapping area of the upper and lower electrodes projected in the cavity of the thin film bulk acoustic wave resonator belongs to the effective resonance area. However, at the connection edge of the resonator, there will be a part of the overlapping area outside the cavity, resulting in the leakage of sound waves to the non-resonant area and generating parasitics, thereby reducing the quality factor Q value of the thin film bulk acoustic wave resonator.

[0007] The present invention aims to solve at least one of the technical problems in the related art to some extent. To this end, an embodiment of the present invention proposes a preparation process for improving the quality factor Q value of a thin film bulk acoustic resonator.

[0008] An embodiment of the present invention also proposes a thin film bulk acoustic resonator, which has a relatively high quality factor Q value.

[0009] The preparation process of the thin film bulk acoustic resonator proposed by the embodiment of the present invention includes the following steps:

[0010] Fabricate a substrate, etch a groove on the substrate and fill a release material in the groove;

[0011] Successively form a lower electrode, a piezoelectric layer and an upper electrode on the substrate continuously to construct a piezoelectric thin film stack structure covering the release material;

[0012] Pattern the upper electrode and the piezoelectric layer so that the projections of the upper electrode and the piezoelectric layer in the direction perpendicular to the substrate are located within the edge of the groove;

[0013] Pattern the lower electrode, and a part of the lower electrode overlaps the substrate.

[0014] The preparation process of the thin film bulk acoustic resonator provided by the embodiment of the present invention has the following beneficial effects:

[0015] The piezoelectric thin film stack structure is deposited continuously, which is different from the conventional processing flow, avoiding the increase in roughness caused by damage to the film surface, and thus avoiding the decrease in the quality factor Q value;

[0016] Optimize the patterns of the upper electrode and the piezoelectric layer. The piezoelectric layer material and the upper electrode material are etched using the same mask plate, and the mask plate pattern is within the substrate groove pattern, so that the effective resonance region all falls within the cavity, avoiding the parasitic problems caused by electrode connection, effectively improving the quality factor Q value of the thin film bulk acoustic resonator, and reducing the acoustic wave loss.

[0017] Optionally, in the step of providing the substrate, the substrate is a high-resistivity silicon wafer.

[0018] Optionally, after etching the groove on the substrate and filling the release material in the groove, the method further includes the step of:

[0019] Adopt a polishing process to grind the release material and the substrate to be flat, so that the upper surface of the release material is flush with the upper surface of the substrate.

[0020] Optionally, before patterning the upper electrode and the piezoelectric layer, the method further includes the step of:

[0021] Form a border layer on the upper electrode and pattern the border layer to form a border pattern.

[0022] Optionally, after patterning the upper electrode and the piezoelectric layer, the outer edge of the border layer, the edge of the upper electrode, and the edge of the piezoelectric layer are flush.

[0023] Optionally, the steps of patterning the upper electrode and the piezoelectric layer specifically include:

[0024] Form a photoresist layer on the upper electrode and pattern the photoresist layer to form a hollow pattern;

[0025] Using the patterned photoresist layer as a mask, etch the upper electrode and the piezoelectric layer.

[0026] Optionally, the edge of the patterned upper electrode and the edge of the piezoelectric layer are flush.

[0027] Optionally, after patterning the lower electrode, the following steps are further included:

[0028] Form an insulating layer to isolate the upper electrode and the lower electrode;

[0029] Etch the insulating layer to form an upper electrode opening communicating with the upper electrode and a lower electrode opening communicating with the lower electrode;

[0030] Form a metal layer that connects the upper electrode and the lower electrode;

[0031] Release the release material to form a cavity, completing the preparation of the thin film bulk acoustic wave resonator.

[0032] Optionally, for wet release of the release material, before forming the insulating layer, the following steps are included:

[0033] Form a protective layer, and in the step of etching the insulating layer to form the upper electrode opening and the lower electrode opening, etching the protective layer is also included.

[0034] The thin film bulk acoustic wave resonator provided by another embodiment of the present invention is made by using the preparation process of the above thin film bulk acoustic wave resonator. Description of the Drawings

[0035] Figure 1 is a schematic structural diagram of the thin film bulk acoustic wave resonator according to an embodiment of the present invention.

[0036] Figure 2 is a top view of the thin film bulk acoustic wave resonator according to an embodiment of the present invention.

[0037] Figures 3 - 10It is a schematic structural diagram in the preparation process of the thin film bulk acoustic wave resonator according to an embodiment of the present invention.

[0038] Figure 11 It is the admittance curve of the thin film bulk acoustic wave resonator in the related art.

[0039] Figure 12 It is the Q-value simulation curve of the thin film bulk acoustic wave resonator in the related art.

[0040] Figure 13 It is the admittance curve of the thin film bulk acoustic wave resonator according to an embodiment of the present invention.

[0041] Figure 14 It is the Q-value simulation curve of the thin film bulk acoustic wave resonator according to an embodiment of the present invention.

[0042] Reference numerals:

[0043] Substrate 100, release material 101, lower electrode 102, piezoelectric layer 103, upper electrode 104, frame layer 105, insulating layer 106, upper electrode opening 107, lower electrode opening 108, metal layer 109, cavity 110. Detailed implementation manners

[0044] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0045] Next, according to Figures 1 - 10 Describe the specific steps of the preparation process of the thin film bulk acoustic wave resonator provided by the embodiments of the present invention, where Figure 1 is the schematic structural diagram of the thin film bulk acoustic wave resonator according to an embodiment of the present invention, Figure 2 is the top view of the thin film bulk acoustic wave resonator according to an embodiment of the present invention, Figures 3 - 10 is the schematic structural diagram in the preparation process of the thin film bulk acoustic wave resonator according to an embodiment of the present invention.

[0046] Step 1: Prepare the substrate 100. The selection of the substrate 100 is familiar to those skilled in the art. For example, the substrate 100 can be a substrate made of single crystal silicon substrate, germanium silicon substrate, germanium substrate or other semiconductor materials well-known to those skilled in the art. Preferably, the substrate 100 is a high-resistance silicon wafer.

[0047] Step 2: As Figure 3As shown, continue on the substrate 100 provided in step 1. Etch a groove on the substrate 100 and fill the groove with a release material 101. Specifically, for example, a photoresist layer may be spin-coated on the upper surface of the substrate 100, and lithography and development are performed to form a hollow pattern. Using the patterned photoresist layer as a mask, the substrate 100 is etched, and then the photoresist layer is removed by a stripping process to form a groove structure on the substrate 100. In this step, the groove etching may be in an inverted V shape, and the angle is preferably greater than 100°.

[0048] Before performing the next step, it may further include the step of: using a polishing process to grind the release material 101 and the substrate 100 to make the upper surface of the release material 101 flush with the upper surface of the substrate 100. It can be understood that the upper surface of the substrate 100 described here is the upper surface of the part of the substrate 100 outside the groove. After the release material 101 is filled into the groove, it may protrude relative to the upper surface of the substrate 100, affecting the deposition quality of the subsequent film layer. Specifically, the polishing process may be a chemical mechanical polishing (CMP) process. Using the CMP process to grind the release material 101 and the substrate 100 is to obtain better film layer deposition quality subsequently.

[0049] Optionally, the release material 101 includes one or more of amorphous silicon, polyimide, silicon oxide, phosphosilicate glass, or borophosphosilicate glass.

[0050] Step 3: As Figure 4 shown, a lower electrode 102, a piezoelectric layer 103, and an upper electrode 104 are continuously formed on the substrate 100 in sequence to construct a piezoelectric thin film stack structure (i.e., a piezoelectric sandwich structure), and the piezoelectric thin film stack structure covers the release material 101. The piezoelectric thin film stack structure provided in the embodiment of the present invention is continuously deposited, omitting processes such as coating, lithography, etching, and stripping in the middle, avoiding the corrosion of the film layer surface caused by these process steps, thereby avoiding the problem of increasing the film layer roughness and making the Q value of the thin film bulk acoustic resonator unaffected. Specifically, the lower electrode 102 is deposited on the substrate 100, then the piezoelectric layer 103 is deposited on the lower electrode 102, and then the upper electrode 104 is deposited on the piezoelectric layer 103. As Figure 4 shown, the deposited piezoelectric thin film stack structure completely covers the release material 101, and the edges of the lower electrode 102, the piezoelectric layer 103, and the upper electrode 104 are flush. That is to say, the edges of the projections of the lower electrode 102, the piezoelectric layer 103, and the upper electrode 104 in the direction perpendicular to the substrate 100 coincide, and are located outside the edge of the projection of the release material 101 in the direction perpendicular to the substrate 100.

[0051] The materials of the lower electrode 102 and the upper electrode 104 can be the same or different, and can be, for example, one or a combination of the following materials: tungsten, silver, zirconium, molybdenum, platinum-platinum, ruthenium, iridium, titanium-tungsten, copper, titanium, chromium, hafnium, aluminum. The materials of the piezoelectric layer 103 include aluminum nitride, zinc oxide, lithium niobate, lithium tantalate, lead zirconate titanate, zinc oxide, lithium tetraborate, and their doped thin films or combinations.

[0052] In addition, before depositing the lower electrode 102 on the substrate 100, a seed layer material can be deposited first to improve the crystal phase of aluminum nitride.

[0053] Step 4: As Figure 5 shown, a border layer 105 is formed on the upper electrode 104, and the border layer is patterned to form a border pattern. The material of the border layer 105 can optionally be molybdenum, aluminum, or tungsten. The addition of the border layer 105 can improve the energy leakage at the edge of the thin film bulk acoustic wave resonator due to impedance mismatch. Specifically, for example, the border layer 105 can be deposited on the upper surface of the upper electrode 104, a photoresist layer is spin-coated on the upper surface of the border layer 105, and a hollow pattern is formed by photolithography and development. Using the patterned photoresist layer as a mask, the border layer 105 is etched, and then the photoresist layer is removed by a lift-off process to form a border pattern.

[0054] Step 5: As Figure 6 shown, the upper electrode 104 and the piezoelectric layer 103 are patterned so that the projections of the upper electrode 104 and the piezoelectric layer 103 in the direction perpendicular to the substrate 100 are within the edge of the groove of the substrate 100, or in other words, the projections of the upper electrode 104 and the piezoelectric layer 103 in the direction perpendicular to the substrate 100 are within the edge of the projection of the release material 101 in the direction perpendicular to the substrate 100. This can ensure that after the release material 101 releases to form a cavity, the overlapping area of the projections of the upper and lower electrodes in the cavity falls within the cavity, avoiding the leakage of acoustic waves to the non-resonant area and eliminating the parasitic problems caused by the extension of the upper electrode connection edge in the thin film bulk acoustic wave resonator structure in the related art, and thus the quality factor Q value of the thin film bulk acoustic wave resonator will not be reduced due to parasitic problems.

[0055] Furthermore, the upper electrode 104 and the piezoelectric layer 103 are patterned into the same photomask, and the upper electrode 104 and the piezoelectric layer 103 are patterned through one photolithography and two etching steps. Specifically, it includes the steps of: forming a photoresist layer on the upper electrode 104, and patterning the photoresist layer to form a hollow pattern, and using the patterned photoresist layer as a mask to etch the upper electrode 104 and the piezoelectric layer 103 in sequence.

[0056] As Figure 6As shown, since the same photomask plate is used, that is, the same photoresist layer is used as the mask, the edges of the upper electrode 104 and the piezoelectric layer 103 after patterning are flush in the direction perpendicular to the substrate 100. Or rather, the edges of the projections of the upper electrode 104 and the piezoelectric layer 103 after patterning in the direction perpendicular to the substrate 100 coincide. Patterning the piezoelectric layer 103 to be consistent with the pattern of the upper electrode 104 can avoid the parasitic problems that may occur between the lower electrode 102 after subsequent metal layer deposition.

[0057] In addition, since the lower electrode, piezoelectric layer, and upper electrode are continuously deposited without processes such as coating, photolithography, and photoresist stripping in between, it avoids the corrosion of the film layer surface caused by excessive process steps, and the Q value of the thin film bulk acoustic wave resonator is not affected to the greatest extent.

[0058] As Figure 6 shown, after patterning the upper electrode 104 and the piezoelectric layer 103, the outer edges of the border layer 105, the edges of the upper electrode 104, and the edges of the piezoelectric layer 103 are all flush.

[0059] Step 6: As Figure 7 shown, pattern the lower electrode 102. A part of the patterned lower electrode 102 overlaps the substrate 100 to ensure the reliability of the thin film bulk acoustic wave resonator. That is to say, a part of the patterned lower electrode 102 covers the groove in the projection in the direction perpendicular to the substrate 100, that is, covers the release material 101, and the other part covers the upper surface of the substrate 100, thus playing a role in supporting the upper electrode 104 and the piezoelectric layer 103 above, making the structure of the thin film bulk acoustic wave resonator reliable. Specifically, it includes the steps of: forming a photoresist layer on the lower electrode 102, patterning the photoresist layer to form a hollow pattern, using the patterned photoresist layer as a mask to etch the lower electrode 102, and stripping the photoresist to complete the patterning of the lower electrode 102.

[0060] As Figure 7 shown, the patterned lower electrode 102 has an opening communicating with the upper surface of the substrate 100. The projection of the patterned lower electrode 102 in the direction perpendicular to the substrate 100 can completely cover the groove, that is, the edge of the projection of the patterned lower electrode 102 in the direction perpendicular to the substrate 100 is located outside the groove.

[0061] Step 7: As Figure 8 shown, form an insulating layer 106 to isolate the upper electrode 104 and the lower electrode 102. The insulating layer 106 is optionally a silicon dioxide layer. Specifically, as Figure 8 shown, on the basis of the structure in step 6, deposit a layer of silicon dioxide as the insulating layer 106 to isolate the upper electrode 104 and the lower electrode 102, avoiding the short - circuit problem caused by subsequent metal layer deposition. As Figure 8As shown, the upper surface of the insulating layer 106 is located above the upper electrode 104 and the frame layer 105.

[0062] Further, after depositing the silicon dioxide layer, the silicon dioxide layer can be thinned to an appropriate thickness to ensure the normal frequency of the final resonator. The thickness of the silicon dioxide layer can be set according to the frequency requirements of the resonator.

[0063] In addition, if wet release is used for the release material 101 subsequently, the wet release process will corrode the silicon dioxide layer. A thin protective layer can be deposited before filling the silicon dioxide to avoid the exposure of the electrode surface caused by the corrosion of the silicon dioxide layer subsequently. Optionally, the material of the protective layer is aluminum nitride.

[0064] Step 8: Etch the insulating layer 106 formed in Step 7 to form an upper electrode opening 107 communicating with the upper electrode 104 and a lower electrode opening 108 communicating with the lower electrode 102. Specifically, as Figure 9 shown, an upper electrode opening 107 is formed in the portion of the insulating layer 106 located above the upper electrode 104 to expose a part of the upper surface of the upper electrode 104. The upper electrode opening 107 also penetrates through a part of the frame layer 105 to expose a part of the frame layer 105. A lower electrode opening 108 is formed in the portion of the insulating layer 106 located above the lower electrode 102 to expose a part of the upper surface of the lower electrode 102. And the projection of the lower electrode opening 108 in the direction perpendicular to the substrate 100 does not fall into the groove of the substrate 100. The edge of the projection of the etched insulating layer 106 in the direction perpendicular to the substrate 100 is located outside the groove of the substrate 100. The specific etching process can adopt the process well-known to those skilled in the art and will not be elaborated here.

[0065] It should be noted that if a thin protective layer is deposited in Step 7, during the process of etching the insulating layer 106 to form the upper electrode opening 107 and the lower electrode opening 108 in this step, it also includes etching the protective layer to expose the lower electrode 102 and the upper electrode 104.

[0066] Step 9: As Figure 10 shown, a PAD metal layer 109 is deposited on the basis of the structure in Step 8. The metal layer 109 is used to connect the upper electrode 104 and the lower electrode 102. The materials of the metal layer 109 can be gold, copper, aluminum, etc. Specifically, as Figure 10 shown, a part of the metal layer 109 fills the upper electrode opening 107 to contact the upper electrode 104, and a part fills the lower electrode opening 108 to contact the lower electrode 102.

[0067] Then, the release material 101 is released to form a cavity 110, and the preparation of the thin film bulk acoustic wave resonator is completed.

[0068] Optionally, the release material 101 can be released by wet etching or gas release. If wet etching is used, the insulating layer 106 formed in step 7 will be etched away together to form a cavity. If gas release is used, the insulating layer 106 formed in step 7 still exists and serves as a passivation layer to protect the electrodes from oxidation. Figure 10 The structural schematic diagram shows the structure with gas release and the insulating layer 106 retained.

[0069] As Figure 1 and Figure 2 shown, the effective resonance region of the fabricated thin film bulk acoustic resonator (i.e., the overlapping region of the upper and lower electrode projections) all falls within the cavity 110, avoiding parasitic problems generated outside the cavity 110 during electrical connection.

[0070] The preparation process of the thin film bulk acoustic resonator provided by the embodiments of the present invention has the following beneficial effects:

[0071] The piezoelectric thin film stack structure is continuously deposited, which is different from the conventional processing flow, avoiding the increase in roughness caused by damage to the film surface, and thus avoiding the decrease in the quality factor Q value.

[0072] The upper electrode and piezoelectric layer patterns are optimized. The piezoelectric layer material and the upper electrode material are etched using the same photomask, and the photomask pattern is within the substrate groove pattern, so that the effective resonance region all falls within the cavity, avoiding parasitic problems caused by electrode connection, effectively improving the quality factor Q value of the thin film bulk acoustic resonator, and reducing acoustic wave loss.

[0073] Another embodiment of the present invention proposes a thin film bulk acoustic resonator, which is fabricated using the preparation process of the above thin film bulk acoustic resonator.

[0074] Figure 11 and Figure 12 are respectively the admittance and Q value simulation curves of the thin film bulk acoustic resonator in the related art. Figure 13 and Figure 14 are respectively the admittance and Q value simulation curves of the thin film bulk acoustic resonator of the embodiments of the present invention. Referring to Figure 11 and Figure 13 's admittance curves, the thin film bulk acoustic resonator in the related art has prominent parasitic clutter both within and outside the resonator frequency, while the thin film bulk acoustic resonator of the embodiments of the present invention does not have this phenomenon. Referring to Figure 12 and Figure 14 's Q value simulation curves, the Q value of the thin film bulk acoustic resonator in the related art is generally below 1100 between the resonance frequencies, while the Q value of the thin film bulk acoustic resonator of the embodiments of the present invention is mostly above 1100, and it is estimated that the Q value can be increased by about 8%. The simulation results prove that the Q value has indeed been significantly improved.

[0075] Therefore, the thin film bulk acoustic wave resonator of the embodiment of the present invention has a high quality factor Q value and less acoustic wave loss.

[0076] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0077] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0078] In the present invention, unless otherwise clearly defined and limited, the terms "mounted", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, or communicable with each other; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0079] In the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "below" and "beneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0080] In the present invention, terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0081] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A preparation process of a thin film bulk acoustic wave resonator, characterized in that, it includes the following steps: Fabricate a substrate, etch a groove on the substrate and fill a release material in the groove; Successively and continuously form a lower electrode, a piezoelectric layer and an upper electrode on the substrate to construct a piezoelectric thin film stack structure covering the release material; Pattern the upper electrode and the piezoelectric layer so that the projections of the upper electrode and the piezoelectric layer in the direction perpendicular to the substrate are within the edge of the groove; Pattern the lower electrode, and a part of the lower electrode overlaps the substrate; The step of patterning the upper electrode and the piezoelectric layer specifically includes: Form a photoresist layer on the upper electrode and pattern the photoresist layer to form a hollow pattern; Using the patterned photoresist layer as a mask, etch the upper electrode and the piezoelectric layer.

2. The preparation process of the thin film bulk acoustic wave resonator according to claim 1, characterized in that, after etching a groove on the substrate and filling a release material in the groove, it further includes the step of: Adopting a polishing process to grind the release material and the substrate to make the upper surface of the release material flush with the upper surface of the substrate.

3. The preparation process of the thin film bulk acoustic wave resonator according to claim 1, characterized in that, in the step of constructing a piezoelectric thin film stack structure covering the release material, the piezoelectric thin film stack structure completely covers the release material.

4. The preparation process of the thin film bulk acoustic wave resonator according to claim 1, characterized in that, before patterning the upper electrode and the piezoelectric layer, it further includes the step of: Form a border layer on the upper electrode and pattern the border layer to form a border pattern.

5. The preparation process of the thin film bulk acoustic wave resonator according to claim 4, characterized in that, after patterning the upper electrode and the piezoelectric layer, the outer edge of the border layer, the edge of the upper electrode and the edge of the piezoelectric layer are flush.

6. The preparation process of the thin film bulk acoustic wave resonator according to claim 1, characterized in that, the edges of the patterned upper electrode and the piezoelectric layer are flush.

7. The preparation process of the thin film bulk acoustic wave resonator according to claim 1, characterized in that, after patterning the lower electrode, it further includes the step of: Form an insulating layer to isolate the upper electrode and the lower electrode; Etch the insulating layer to form an upper electrode opening communicating with the upper electrode and a lower electrode opening communicating with the lower electrode; Form a metal layer, and the metal layer connects the upper electrode and the lower electrode; Release the release material to form a cavity, and complete the preparation of the thin film bulk acoustic wave resonator.

8. The preparation process of the thin film bulk acoustic wave resonator according to claim 7, characterized in that, for wet release of the release material, before forming the insulating layer, it includes the following steps: Form a protective layer, and in the step of etching the insulating layer to form the upper electrode opening and the lower electrode opening, it also includes etching the protective layer.

9. A thin film bulk acoustic wave resonator, characterized in that, The thin film bulk acoustic wave resonator is fabricated by using the fabrication process of the thin film bulk acoustic wave resonator according to any one of claims 1-8.

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