CN112117988A

CN112117988A - Bulk acoustic wave resonator, method of manufacturing the same, filter, and electronic apparatus

Info

Publication number: CN112117988A
Application number: CN202010519683.7A
Authority: CN
Inventors: 黄河
Original assignee: Smic Ningbo Co ltd Shanghai Branch
Current assignee: Smic Ningbo Co ltd Shanghai Branch; Ningbo Semiconductor International Corp Shanghai Branch
Priority date: 2020-06-09
Filing date: 2020-06-09
Publication date: 2020-12-22
Also published as: WO2021248866A1

Abstract

A bulk acoustic wave resonator, a method of manufacturing the bulk acoustic wave resonator, a filter, and an electronic apparatus, the method of manufacturing the bulk acoustic wave resonator comprising: providing a substrate, wherein a groove is formed in the substrate; forming a sacrificial layer in the groove; forming a bottom electrode on the sacrificial layer, wherein part of the boundary of the bottom electrode is positioned above the groove, and part of the boundary extends to the substrate on the periphery of the groove; forming a flat layer which is positioned on the substrate exposed by the bottom electrode and is contacted with the side wall of the bottom electrode, wherein the top surface of the flat layer is flush with the top surface of the bottom electrode; forming a piezoelectric layer overlying the bottom electrode and the planarization layer; forming a top electrode on the piezoelectric layer, the piezoelectric acoustic resonance stack including a bottom electrode, the piezoelectric layer, and the top electrode; forming a release hole through the piezoelectric acoustic resonance stack; the sacrificial layer is removed through the release hole to form a cavity. The invention forms the bottom electrode and the flat layer, provides a flat surface for the formation of the piezoelectric layer, and enables the piezoelectric layer to keep flat, thereby eliminating boundary standing waves and noise waves and further improving the quality factor of the resonator.

Description

Bulk acoustic wave resonator, method of manufacturing the same, filter, and electronic apparatus

Technical Field

The embodiment of the invention relates to the field of semiconductor manufacturing, in particular to a bulk acoustic wave resonator, a manufacturing method thereof, a filter and electronic equipment.

Background

With the development of wireless communication technology, the traditional single-band single-standard equipment cannot meet the requirement of diversification of communication systems. Currently, communication systems are increasingly moving towards multiple frequency bands, which requires that communication terminals can accept each frequency band to meet the requirements of different communication service providers and different regions.

RF (radio frequency) filters are typically used to pass or block particular frequencies or frequency bands in RF signals. In order to meet the development requirements of wireless communication technology, an RF filter used in a communication terminal is required to meet the requirements of multiband and multi-mode communication technologies, and meanwhile, the RF filter in the communication terminal is required to be continuously developed towards miniaturization and integration, and one or more RF filters are adopted in each frequency band.

The most important metrics for an RF filter include quality factor Q and insertion loss. As the frequency difference between different frequency bands becomes smaller and smaller, the RF filter needs to have very good selectivity to pass signals in the frequency band and to block signals outside the frequency band. The larger the Q value, the narrower the passband bandwidth can be achieved by the RF filter, resulting in better selectivity.

Disclosure of Invention

Embodiments of the present invention provide a bulk acoustic wave resonator, a method for manufacturing the bulk acoustic wave resonator, a filter, and an electronic device, which improve a quality factor of the bulk acoustic wave resonator.

In order to solve the above problem, an embodiment of the present invention provides a method for manufacturing a bulk acoustic wave resonator, including: providing a substrate, wherein a groove is formed in the substrate; filling the groove to form a sacrificial layer positioned in the groove; forming a bottom electrode on the sacrificial layer, wherein part of the boundary of the bottom electrode is positioned above the groove, and part of the boundary extends to the substrate on the periphery of the groove; forming a flat layer which is positioned on the substrate exposed by the bottom electrode and is contacted with the side wall of the bottom electrode, wherein the top surface of the flat layer is flush with the top surface of the bottom electrode; forming a piezoelectric layer overlying the bottom electrode and the planarization layer; forming a top electrode on the piezoelectric layer, the piezoelectric acoustic resonance stack comprising a bottom electrode, the piezoelectric layer, and the top electrode; forming a release hole through the acoustic transducer; and removing the sacrificial layer through the release hole to form a cavity.

Correspondingly, an embodiment of the present invention further provides a bulk acoustic wave resonator, including: a substrate having a cavity therein; a piezoelectric acoustic resonance stack located on the substrate, the piezoelectric acoustic resonance stack including a bottom electrode partially bounded on the cavity and extending partially outside the cavity, a piezoelectric layer located on the bottom electrode and having a flat extension at an end of the bottom electrode, and a top electrode located on an upper surface of the piezoelectric layer; the flat layer is positioned on the same layer as the bottom electrode, the top surface of the flat layer is flush with the top surface of the bottom electrode, and a gap is formed between the flat layer and the bottom electrode; a release aperture extending through the acoustic transducer and communicating with the cavity.

Correspondingly, an embodiment of the present invention further provides another bulk acoustic wave resonator, including: a substrate having a cavity therein; a piezoelectric acoustic resonance stack located on the substrate, the piezoelectric acoustic resonance stack including a bottom electrode partially bounded on the cavity and extending partially outside the cavity, a piezoelectric layer located on the bottom electrode and having a flat extension at an end of the bottom electrode, and a top electrode located on an upper surface of the piezoelectric layer; the flat layer and the bottom electrode are positioned on the same layer, the top surface of the flat layer is flush with the top surface of the bottom electrode, and the flat layer is in contact with the bottom electrode and covers the substrate exposed by the bottom electrode; a release aperture extending through the piezoelectric acoustic resonance stack and communicating with the cavity.

Correspondingly, the embodiment of the invention also provides a filter, which comprises the bulk acoustic wave resonator provided by the first embodiment of the invention.

Correspondingly, the embodiment of the invention also provides another filter, which comprises the bulk acoustic wave resonator provided by the second embodiment of the invention.

Correspondingly, the embodiment of the invention also provides electronic equipment, which comprises the filter provided by the first embodiment of the invention.

Correspondingly, the embodiment of the invention also provides another electronic device, which comprises the filter provided by the second embodiment of the invention.

Compared with the prior art, the technical scheme of the embodiment of the invention has the following advantages:

in the method for manufacturing a bulk acoustic wave resonator provided by the embodiment of the invention, after the groove in the substrate is filled with the sacrificial layer, the bottom electrode on the sacrificial layer is formed, part of the boundary of the bottom electrode is positioned above the groove, part of the boundary extends to the substrate at the periphery of the groove, and the flat layer which is positioned on the substrate exposed by the bottom electrode and is contacted with the side wall of the bottom electrode is formed, the top surface of the flat layer is flush with the top surface of the bottom electrode, so that a flat surface is provided for the formation of the piezoelectric layer, correspondingly, after the piezoelectric layer covering the bottom electrode and the flat layer is formed, the piezoelectric layer can not cover the side wall of the bottom electrode, the piezoelectric layer can be kept flat at the boundary of the piezoelectric layer and the bottom electrode, and can have better lattice orientation, thereby improving the performance of the resonator, and avoiding the problem of abrupt change of the boundary structure caused by bending of the, accordingly, the problem of boundary disturbance of the sound wave can be avoided, so that boundary standing waves and clutter can be eliminated, and the quality factor of the resonator can be improved.

In the alternative, the method for forming the flat layer comprises the following steps: forming a first sub-flat layer on the substrate at the periphery of the groove, wherein a gap is formed by the first sub-flat layer and the bottom electrode, and the top surface of the first sub-flat layer is flush with the top surface of the bottom electrode; by forming a gap between the bottom electrode and the first sub-planarization layer, the bottom electrode is exposed in the gap, so that the loss of transverse waves can be further prevented, thereby improving the quality factor of the resonator.

In an alternative scheme, the first sub-flat layer is made of an insulating material, so that the existence of upper and lower opposite conductive layers at the periphery of an effective resonance area can be avoided, a parasitic resonance effect is avoided, and the performance of the resonator can be better improved.

Drawings

Fig. 1 to 2 are schematic structural diagrams corresponding to respective steps in a method for manufacturing a bulk acoustic wave resonator;

fig. 3 to 12 are schematic structural diagrams corresponding to steps in an embodiment of a method for manufacturing a bulk acoustic wave resonator according to the present invention;

fig. 13 to 15 are schematic structural diagrams corresponding to steps in another embodiment of the method for manufacturing a bulk acoustic wave resonator according to the present invention.

Detailed Description

At present, the quality factor of the bulk acoustic wave resonator still needs to be improved. The reason why the quality factor of the bulk acoustic wave resonator is still to be improved is analyzed in conjunction with a method of manufacturing the bulk acoustic wave resonator. Fig. 1 to 2 are schematic structural diagrams corresponding to respective steps in a manufacturing method of a resonator.

Referring to fig. 1, a substrate 10 is provided, the substrate 10 having a sacrificial layer 30 formed therein, the substrate 10 exposing a top surface of the sacrificial layer 30. Referring to fig. 2, a piezoelectric acoustic resonance stack (not labeled) is formed on the sacrificial layer 30, the piezoelectric acoustic resonance stack including a bottom electrode 40, a piezoelectric layer 50 covering the bottom electrode 40, and a top electrode 60 covering the piezoelectric layer 50.

Wherein, part of the boundary of the bottom electrode 40 is located above the sacrificial layer 30, and part of the boundary extends to the substrate 10 at the periphery of the sacrificial layer 30, therefore, the piezoelectric layer 50 covers not only the top of the bottom electrode 40, but also the side wall of the bottom electrode 40, which in turn causes the piezoelectric layer 50 to bend at the end position of the bottom electrode 40 (as shown by the dashed circle in fig. 2), thereby generating a sudden change of the boundary structure, which in turn is easy to generate boundary disturbance to the acoustic wave, thereby generating boundary standing waves and noise waves, and in turn causing the quality factor of the resonator to decrease.

In order to solve the technical problem, in the embodiments of the present invention, a bottom electrode is formed on a sacrificial layer, a part of a boundary of the bottom electrode is located above a groove, a part of the boundary extends to a substrate at the periphery of the groove, and a flat layer is formed on the substrate exposed by the bottom electrode and in contact with a sidewall of the bottom electrode, a top surface of the flat layer is flush with a top surface of the bottom electrode, which provides a flat surface for forming a piezoelectric layer, accordingly, after the piezoelectric layer covering the bottom electrode and the flat layer is formed, the piezoelectric layer does not cover the sidewall of the bottom electrode, the piezoelectric layer can be kept flat at the boundary between the piezoelectric layer and the bottom electrode, and can have a better lattice orientation, so that the performance of a resonator can be improved, and a problem of abrupt change of a boundary structure caused by bending of the piezoelectric layer at an end position of the bottom electrode can be avoided, therefore, boundary standing waves and clutter can be eliminated, and the quality factor of the resonator can be improved.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Fig. 3 to 12 are schematic structural diagrams corresponding to steps in an embodiment of a method for manufacturing a bulk acoustic wave resonator according to the present invention.

Referring to fig. 3, including fig. 3a and 3b, fig. 3a is a cross-sectional view along a first direction, and fig. 3b is a cross-sectional view along a second direction, the first direction and the second direction being perpendicular, a substrate 100 is provided, the substrate 100 having a groove 110 formed therein.

The manufacturing method is used for forming bulk acoustic wave resonators (resonators), which refer to devices that generate a resonance frequency. Specifically, the bulk acoustic resonator is a Film Bulk Acoustic Resonator (FBAR), which is mainly composed of a bottom electrode, a top electrode, and a piezoelectric layer therebetween. The FBAR has excellent characteristics of small size, high resonant frequency, high Q value, large power capacity, good roll-off effect, and the like.

The substrate 100 is used to provide a process platform for the fabrication of bulk acoustic wave resonators. In this embodiment, the substrate 100 is a wafer-level substrate 100, and the substrate 100 is formed based on a CMOS process. By manufacturing the bulk acoustic wave resonator on the wafer, the process cost can be reduced, and the mass production can be realized, which is beneficial to improving the reliability of the bulk acoustic wave resonator and improving the manufacturing efficiency.

The substrate 100 is used for forming a piezoelectric acoustic resonance lamination, and the piezoelectric acoustic resonance lamination comprises a bottom electrode, a piezoelectric layer and a top electrode which are sequentially stacked from bottom to top, so that a full-film processing technology is realized, and the process cost is reduced. In this embodiment, the substrate 100 includes an active resonance region and an inactive region. The region on the groove 110 where the top electrode overlaps the bottom electrode is an active resonance region, and the remaining region is an inactive region.

The recess 110 serves as a cavity after subsequent formation of the piezoelectric acoustic resonance stack. Thus, the shape, location and size of the recess 110 determines the shape, location and size of the subsequent cavity, and accordingly, the recess 110 is formed according to the shape, location and size of the desired cavity. As an example, the longitudinal cross-sectional shape of the groove 110 is an inverted trapezoid, i.e., the groove 110 includes four sidewalls, and the top dimension of the groove 110 is greater than the bottom dimension. The size of the top of the groove 110 is larger than that of the bottom, so as to facilitate the filling and removal of the subsequent sacrificial layer, and the leaked sound waves are easy to realize total reflection at the junction of the bottom electrode and the air. The number of the grooves 110 is at least one.

In this embodiment, the substrate 100 includes a plurality of resonator unit regions (not shown), and each resonator unit region has a recess 110 formed therein, so that the number of the recesses 110 is plural, so as to form a plurality of bulk acoustic wave resonators on the substrate 100, thereby realizing mass production. Here, for convenience of illustration, only one resonator element region is illustrated in fig. 3.

With continued reference to fig. 3, the method of manufacturing further comprises: an etch stop layer 120 is formed on the substrate 100, the etch stop layer 120 also conformally covering the bottom and sidewalls of the recess 110.

A bottom electrode is subsequently formed on the substrate 100 and the etch stop layer 120 is used to achieve electrical isolation of the substrate 100 from the bottom electrode. Also, the process of forming the bottom electrode includes a deposition process and an etching process which are sequentially performed, and the etch stop layer 120 serves to define an etch stop position during the process of forming the bottom electrode, thereby reducing damage to the substrate 100. In addition, a sacrificial layer is formed in the groove 110, the process of forming the sacrificial layer includes a planarization process, and the etch stop layer 120 is further used for defining a stop position of the planarization process, so as to facilitate improvement of the surface flatness of the sacrificial layer.

The material of the etch stop layer 120 is an insulating material, so as to electrically isolate the substrate 100 from the bottom electrode, and the material of the etch stop layer 120 includes one or more of silicon oxide, silicon nitride, and silicon oxynitride. In this embodiment, the material of the etch stop layer 120 is silicon oxide, which enables the etch stop layer 120 to also function as a stress buffer. In particular, when a metal material is subsequently formed on the substrate 100, the etch stop layer 120 can serve as a stress buffer, thereby improving the film formation quality of the metal material.

In this embodiment, the etching stop layer 120 is formed by a deposition process, which may be a chemical vapor deposition process or an atomic layer deposition process.

The thickness of the etch stop layer 120 should not be too small, nor too large. If the thickness is too small, the above-mentioned properties of the etch stop layer 120 are difficult to be secured; if the thickness of the film is too large, the flatness of the film is difficult to ensure, and the formation quality of a subsequent film layer is influenced. Therefore, in the present embodiment, the thickness of the etch stop layer 120 is 50 nm to 1000 nm. For example, the etch stop layer 120 may have a thickness of 100 nanometers, 300 nanometers, 500 nanometers, 700 nanometers, or 900 nanometers.

Referring to fig. 4, including fig. 4a and 4b, fig. 4a is a cross-sectional view based on fig. 3a, and fig. 4b is a cross-sectional view based on fig. 3b, the groove 110 is filled, and the sacrificial layer 130 located in the groove 110 is formed.

The sacrificial layer 130 fills the recess 110 to provide a process platform for subsequent formation of the piezoelectric acoustic resonance stack. Moreover, after the groove 110 is filled with the sacrificial layer 130, a flat surface can be provided for the subsequent formation of each functional layer, thereby being beneficial to improving the formation quality of each functional layer.

The sacrificial layer 130 is subsequently removed, the sacrificial layer 130 is made of a material that is easy to remove, and the process of removing the sacrificial layer 130 has little effect on the piezoelectric acoustic resonance stack. The material of the sacrificial layer 130 includes one or more of silicon oxide, carbon-containing compound and germanium, wherein the carbon atom percentage content in the carbon-containing compound is greater than 50% to facilitate the removal of the sacrificial layer 130. For example, the carbon-containing compound includes amorphous carbon.

In this embodiment, the material of the sacrificial layer 130 is amorphous carbon. The amorphous carbon material is low in cost and can be removed through an ashing process in the follow-up process, the ashing process has little damage to the piezoelectric acoustic resonance laminated layer, and oxygen-containing gas adopted by the ashing process can oxidize the amorphous carbon into carbon dioxide, so that reaction byproducts are directly discharged from the reaction chamber, the risk of generating the residual sacrificial layer 130 is favorably reduced, the probability of the residual reaction byproducts in the cavity is reduced, and the reliability of the bulk acoustic wave resonator is correspondingly favorably improved.

Specifically, the sacrificial layer 130 having a top surface flush with the top surface of the etch stop layer 120 is formed by deposition of a corresponding material and planarization treatment (e.g., a chemical mechanical polishing process). Wherein the planarization process takes the top surface of the etch stop layer 120 as a stop location.

Referring to fig. 5, including fig. 5a and 5b, fig. 5a is a cross-sectional view based on fig. 4a, and fig. 5b is a cross-sectional view based on fig. 4b, a bottom electrode 140 is formed on the sacrificial layer 130, and a portion of the boundary of the bottom electrode 140 is located above the recess 110 (shown in fig. 3) and partially extends to the substrate 100 at the periphery of the recess 110.

Specifically, the bottom electrode 140 covers a portion of the sacrificial layer 130 and extends onto the etch stop layer 120 at the periphery of the recess 110. In this embodiment, the substrate 100 includes a plurality of resonator unit regions (not shown), and each resonator unit region has a recess 110 formed therein, so that the number of the bottom electrodes 140 is correspondingly multiple, the bottom electrodes 140 are separately disposed, and the bottom electrodes 140 and the resonator unit regions correspond to each other one by one.

The material of the bottom electrode 140 may be a conductive material such as metal, metal silicide, metal nitride, metal oxide, or conductive carbon, for example, Mo, Al, Cu, Ag, Au, Ni, Co, TiAl, TiN, or TaN. In this embodiment, the bottom electrode 140 is made of Mo. Specifically, the bottom electrode 140 is formed through a deposition process and an etching process, which are sequentially performed.

In this embodiment, the shape of the effective resonance region may be any shape, for example, a square, a circle, a pentagon, a hexagon, or an irregular polygon.

In the piezoelectric acoustic resonance stack, a portion of the three-layer stack structure having the bottom electrode 140, the piezoelectric layer, and the top electrode, which is located above the cavity, serves as an effective functional layer, an area corresponding to the effective functional layer serves as an effective resonance area, and the remaining area is an inactive area. In this embodiment, a part of the boundary of the bottom electrode 140 is located above the groove 110, the cavity medium is different from the medium of the stacked structure, the acoustic impedance is different, and the sound wave is reflected at the interface where the acoustic impedance is not matched, so that the effect of reflecting the sound wave is realized to maintain the oscillation. In which parasitic capacitance is easily generated in the piezoelectric acoustic resonance stack of the inactive region, the bottom electrode 140 is exposed to a portion of the sacrificial layer 130 to isolate the active resonance region from the inactive region, thereby reducing the influence of the parasitic capacitance on the piezoelectric acoustic resonance stack located in the active resonance region.

Referring collectively to fig. 6-8, a planarization layer 500 (shown in fig. 8) is formed on the substrate 100 where the bottom electrode 140 is exposed and in contact with the sidewalls of the bottom electrode 140, the top surface of the planarization layer 500 being flush with the top surface of the bottom electrode 140.

The piezoelectric layer covering the bottom electrode 140 and the flat layer 500 is formed subsequently, the flat layer 500 is used for covering the exposed area of the bottom electrode 140, the top surface of the flat layer 500 is flush with the top surface of the bottom electrode 140, a flat surface is provided for the formation of the piezoelectric layer, the piezoelectric layer does not cover the side wall of the bottom electrode 140 correspondingly, at the junction of the piezoelectric layer and the bottom electrode 140, the piezoelectric layer can be kept flat and smooth and can have better lattice orientation, the performance of the resonator can be improved, the problem of sudden change of the boundary structure caused by bending of the piezoelectric layer at the end position of the bottom electrode 140 can be avoided, the problem of boundary disturbance of sound waves is correspondingly avoided, the problem of boundary standing waves and clutter is favorably eliminated, and the quality factor of the bulk acoustic wave resonator is improved.

In this embodiment, the planarization layer 500 includes a first sub-planarization layer 150 and a second sub-planarization layer 160 located between the bottom electrode 140 and the first sub-planarization layer 150.

Specifically, referring to fig. 6, including fig. 6a and 6b, fig. 6a is a cross-sectional view based on fig. 5a, and fig. 6b is a cross-sectional view based on fig. 5b, a first sub-planarization layer 150 is formed on the substrate 100 at the periphery of the recess 110 (shown in fig. 3), the first sub-planarization layer 150 encloses a gap 155 with the bottom electrode 140, and the top surface of the first sub-planarization layer 150 is flush with the top surface of the bottom electrode 140.

The gap 155 is used to provide a spatial location for the formation of the second sub-planar layer. When the second sub-planarization layer is formed in the gap 155, the process of forming the second sub-planarization layer includes a planarization process, in this embodiment, the first sub-planarization layer 150 is formed first to cover most of the area, which is beneficial to improving the dishing (dishing) problem of the planarization process when the second sub-planarization layer is formed, so as to be beneficial to improving the top surface planarization of the second sub-planarization layer, and accordingly, the top surface planarization of the planarization layer is improved, and further, the planarization of the subsequent piezoelectric layer is improved.

In this embodiment, the gap 155 extends along the boundary of the effective resonance region. After a release hole penetrating through the piezoelectric acoustic resonance laminated layer is formed subsequently, the second sub-planarization layer is removed through the release hole, so that an opening (not labeled) is formed between the bottom electrode 140 and the first sub-planarization layer 150, the bottom electrode 140 is exposed in the opening, an air medium in the opening is different from the material of the bottom electrode 140, and a mismatched acoustic impedance interface can be formed, so that the transverse wave is reflected, the transverse wave loss is further prevented, and the quality factor (Q value) of the bulk acoustic wave resonator is improved. Therefore, by extending the gap 155 along the boundary of the effective resonance region, the sidewall of the bottom electrode 140 can be brought into contact with the air medium.

As an example, the first sub-planar layer 150 encloses a closed annular gap 155 with a part of the boundary of the top electrode 140, i.e. the first sub-planar layer 150 surrounds the top electrode 140 with a gap 155 with the top electrode 140. In other embodiments, the first sub-planar layer encloses a ring with a gap with a portion of the boundary of the top electrode. For example, when the shape of the effective resonance region is a pentagon, the first sub-flat layer and four sides of the top electrode enclose a ring shape with gaps.

The width of the gap 155 should not be too small, nor too large. If the width of the gap 155 is too small, it is difficult to fill the material of the second sub-planarization layer in the gap 155, which easily results in low planarization of the top surface of the second sub-planarization layer, and accordingly it is difficult to improve the planarization of the piezoelectric layer; if the width of the gap 155 is too large, the effect of improving the dishing problem is not good when the second sub-planarization layer is formed subsequently, which is not favorable for improving the flatness of the top surface of the second sub-planarization layer, and thus it is difficult to improve the flatness of the piezoelectric layer. In the present embodiment, the width of the gap 155 is 1 nm to 100 nm. For example, the gap 155 may have a width of 10 nanometers, 30 nanometers, 50 nanometers, 70 nanometers, or 90 nanometers.

In this embodiment, the first sub-planarization layer 150 is made of an insulating material, which can prevent the existence of upper and lower opposite conductive layers at the periphery of the effective resonance area, thereby preventing the generation of parasitic resonance effect. Specifically, the material of the first sub-planarization layer 150 includes one or more of silicon oxide, silicon nitride, carbon-containing compound, and germanium, wherein the carbon atom percentage in the carbon-containing compound is greater than 50%. As an example, the material of the first sub-planarization layer 150 is silicon nitride. The silicon nitride has a high dielectric constant, a good insulating effect, and a high density, and when the second sub-flat layer is subsequently removed through the release holes, the first sub-flat layer 150 has a low probability of being worn. In other embodiments, the material of the first planarization layer may also be silicon oxide. Therefore, in the present embodiment, the step of forming the first sub-planarization layer 150 includes: forming a first sub planarization film conformally covering the bottom electrode 140, and the substrate 100 and the sacrificial layer 130 where the bottom electrode 140 is exposed; the first sub planarization film is patterned to form a first sub planarization layer 15. Specifically, the first sub-planarization film is patterned using a dry etching process (e.g., an anisotropic dry etching process). The anisotropic dry etching process has anisotropic etching characteristics, and is beneficial to improving the sidewall morphology quality and the dimensional accuracy of the first sub-flat layer 150.

In other embodiments, the material of the first sub-planarization layer may also be a metal material, and accordingly, after the bottom electrode is formed, the first sub-planarization layer may also be formed through a metal lift-off (lift-off) process. By adopting the metal stripping process, the metal material is not required to be etched, so that the problem that the bottom electrode 140 is damaged by etching is avoided, and the quality of the bottom electrode 140 is ensured.

In this embodiment, the bottom electrode 140 is formed first, and then the first sub-planarization layer 150 is formed. In other embodiments, the first sub-planarization layer may be formed first, and then the bottom electrode may be formed. Accordingly, in order to improve the quality of the formation of the bottom electrode and prevent the formation of the bottom electrode in an area where the formation of the bottom electrode is not required, a metal lift off (lift off) process is used to form the bottom electrode, thereby improving the quality of the bottom electrode. In other embodiments, to simplify the process steps, the material of the bottom electrode is the same as the material of the first sub-planarization layer, and in the same step, the bottom electrode and the first sub-planarization layer are formed.

Referring to fig. 7 to 8 in combination, a second sub-planarization layer 160 is formed in the gap 155 (as shown in fig. 6), the top surface of the second sub-planarization layer 160 is flush with the top surface of the bottom electrode 140, and the second sub-planarization layer 160 and the first sub-planarization layer 150 are used to form a planarization layer 500 (as shown in fig. 8).

In this embodiment, the second sub-planarization layer 160 covers the sacrificial layer 130 exposed by the bottom electrode 140. Therefore, when the release hole is formed subsequently, the second flat layer 160 can be exposed at the bottom of the release hole, and the sacrificial layer 130 can be released continuously after the second flat layer 160 is released through the release hole, so that the process difficulty of forming the release hole is reduced, and the process time of forming the release hole is reduced.

The second sub-planarization layer 160 is an insulating material, which is beneficial to improve the parasitic resonance effect when the second sub-planarization layer 160 is remained. Specifically, the material of the second sub-planarization layer 160 includes one or more of silicon oxide, silicon nitride, carbon-containing compound, and germanium, wherein the carbon atom percentage content in the carbon-containing compound is greater than 50%. By selecting the above materials, the influence on the bottom electrode 140 is small when the second sub-planarization layer 160 is removed later. In this embodiment, the materials of the second sub-planarization layer 160 and the sacrificial layer 130 are the same, so that the second sub-planarization layer 160 and the sacrificial layer 130 can be removed in the same process, thereby simplifying the process complexity. Accordingly, the material of the second sub-planarization layer 160 is amorphous carbon. In other embodiments, the materials of the second sub-planarization layer and the sacrificial layer may also be different.

Specifically, referring to fig. 7 including fig. 7a and 7b, fig. 7a is a sectional view based on fig. 6a, fig. 7b is a sectional view based on fig. 6b, the second sub planarization film 165 is filled in the gap 155, and the second sub planarization film 165 also covers the first sub planarization layer 150 and the bottom electrode 140.

The second sub-planarization film 165 in the gap 155 is subsequently left as a second sub-planarization layer.

In the present embodiment, the second sub planarization film 165 is formed using a deposition process, and thus, after the second sub planarization film 165 is formed, the second sub planarization film 165 covers the entire top surfaces of the first planarization layer 150 and the bottom electrode 140. In this embodiment, after the second sub-planarization film 165 is formed, the second sub-planarization films 165 on both sides of the gap 155 are etched, so that the remaining second sub-planarization films 165 cover a portion of the first sub-planarization layer 150 and a portion of the bottom electrode 140 on both sides of the gap 155. By removing most of the second sub-planarization film 165 on the top surfaces of the first sub-planarization layer 150 and the bottom electrode 140, the process difficulty of the subsequent planarization process is reduced, thereby improving the top surface planarization of the second sub-planarization layer.

Specifically, the second sub planarization films 165 on both sides of the gap 155 are etched using a dry etching process (e.g., an anisotropic dry etching process). The anisotropic dry etching process is advantageous in reducing the probability of damage to the second sub-planarization film 165 in the gap 155. Moreover, the second sub-planarization layer 160 is an insulating material, and the influence of etching the insulating material on the bottom electrode 140 is small.

Referring to fig. 8, including fig. 8a and 8b, fig. 8a is a cross-sectional view based on fig. 7a, and fig. 8b is a cross-sectional view based on fig. 7b, the second sub planarization film 165 (shown in fig. 7) is planarized, the second sub planarization film 165 located on the top surfaces of the first planarization layer 150 and the bottom electrode 140 is removed, and the top surface of the remaining second sub planarization film 165 in the gap 155 is made flush with the top surface of the bottom electrode 140, and the remaining second sub planarization film 165 serves as the second sub planarization layer 160.

In this embodiment, a chemical mechanical polishing process is used to perform planarization. In other embodiments, the second sub-planarization film may not be etched before being planarized, depending on the actual situation.

Referring to fig. 9, including fig. 9a and 9b, fig. 9a is a sectional view based on fig. 8a, and fig. 9b is a sectional view based on fig. 8b, a piezoelectric layer 170 covering the bottom electrode 140 and the planarization layer 500 is formed.

During operation of the bulk acoustic wave resonator, a bulk acoustic wave is excited in the piezoelectric layer 170 by applying a radio frequency voltage across the bottom electrode 140 and the top electrode, thereby completing resonance.

The material of the piezoelectric layer 170 may be a piezoelectric crystal, a piezoelectric ceramic, a piezoelectric polymer, or the like. The piezoelectric crystal can be aluminum nitride, lead zirconate titanate, quartz crystal, lithium gallate, lithium germanate, titanium germanate, lithium niobate or lithium tantalate, and the piezoelectric polymer can be polyvinylidene fluoride, vinylidene fluoride-trifluoroethylene copolymer, nylon-11 or vinylidene cyanide-vinyl acetate alternating copolymer, and the like. In this embodiment, the piezoelectric layer 170 is made of aluminum nitride. Aluminum nitride has the advantage of exhibiting a piezoelectric coupling coefficient of about 6.5% and exhibiting low acoustic and dielectric losses, thereby causing the bulk acoustic wave resonator to exhibit a passband that matches the specifications required by most telecommunications standards.

Referring to fig. 10, including fig. 10a and 10b, fig. 10a is a cross-sectional view based on fig. 9a, and fig. 10b is a cross-sectional view based on fig. 9b, a Top electrode (Top electrode)180 is formed on a piezoelectric layer 170, and a piezoelectric acoustic resonance stack 550 includes a bottom electrode 140, a Top electrode 180, and the piezoelectric layer 170.

The bottom electrode 140, the top electrode 180 and the piezoelectric layer 170 are used to form a piezoelectric acoustic resonance stack 550, and the piezoelectric acoustic resonance stack 550 is used to realize interconversion between an electrical signal and an acoustic signal, so that the bulk acoustic wave resonator performs filtering processing on the signal.

The material of the top electrode 180 may be a conductive material such as metal, metal silicide, metal nitride, metal oxide, or conductive carbon, for example, Mo, Al, Cu, Ag, Au, Ni, Co, TiAl, TiN, or TaN. In this embodiment, the material of the top electrode 180 is Mo. Specifically, the top electrode 180 is formed by deposition and etching of the respective materials.

In this embodiment, the top electrode 180 is formed by deposition and etching of the corresponding material. In this embodiment, a part of the boundary of the top electrode 180 is located on the recess 110 (as shown in fig. 3), and a part of the boundary extends to the substrate 100 at the periphery of the recess 110, so that the top electrode 180 exposes a part of the piezoelectric layer 170 above the sacrificial layer 130, and accordingly, in the subsequent process of forming the release hole penetrating through the piezoelectric acoustic resonance stack 550, the release hole may not penetrate through three layers, namely the top electrode 180, the piezoelectric layer 170, and the bottom electrode 160, thereby being beneficial to reducing the difficulty of the process for forming the release hole. In this embodiment, the top electrode 180 and the bottom electrode 170 in the inactive area are staggered from each other, so that the parasitic capacitance generated by the piezoelectric acoustic resonance stack in the inactive area is reduced, and the parasitic resonance effect is improved.

Referring to fig. 11, including fig. 11a and 11b, fig. 11a is a sectional view based on fig. 10a, and fig. 11b is a sectional view based on fig. 10b, a relief hole 190 is formed through the piezoelectric acoustic resonance stack 550.

The release holes 190 are located on the sacrificial layer 130, and the sacrificial layer 130 can be subsequently removed through the release holes 190. In this embodiment, the number of the release holes 190 is multiple, so as to improve the efficiency of removing the sacrificial layer 130 through the release holes 190.

In this embodiment, the release holes 190 penetrate through the top electrode 180 or the bottom electrode 170, that is, the release holes 190 penetrate through the piezoelectric acoustic resonance stack 550 located in the inactive region, but do not penetrate through the piezoelectric acoustic resonance stack 550 located in the active resonance region, so that the piezoelectric acoustic resonance stack 550 located in the active resonance region is not etched in the process of forming the release holes 190, which is beneficial to reducing the influence on the piezoelectric acoustic resonance stack 550 located in the active resonance region, and is beneficial to improving the performance of the bulk acoustic wave resonator.

Specifically, depending on the formation location of the release hole 190 and the stack structure of the piezoelectric acoustic resonance stack 550 corresponding to the location, the release hole 190 may penetrate the top electrode 180 and the piezoelectric layer 170 and expose a portion of the top of the planarization layer 500; alternatively, the release hole 190 penetrates through the piezoelectric layer 170 and the planarization layer 500 and exposes a portion of the top of the sacrificial layer 130; alternatively, the release hole 190 penetrates the top electrode 180, the piezoelectric layer 170, and the planarization layer 500 and exposes a portion of the top of the sacrificial layer 130. As an example, the release hole 190 penetrates the top electrode 180, the piezoelectric layer 170, and the second sub planarization layer 160 and exposes a portion of the top of the sacrificial layer 130. The second sub-planarization layer 160 is removed later, so that the second sub-planarization layer 160 and the sacrificial layer 130 can be removed later at the same time by penetrating the release hole 190 through the second sub-planarization layer 160, thereby improving the manufacturing efficiency. In other embodiments, a portion of the release holes penetrate through the second sub-planarization layer, and the bottoms of the remaining release holes expose the second sub-planarization layer.

The step of forming the release hole 190 includes: forming a mask layer (not shown) over the piezoelectric acoustic resonance stack 550, the mask layer having an opening (not shown) formed therein over the sacrificial layer 130; the piezoelectric acoustic resonance stack 550 under the opening is etched using the mask layer as a mask to form the release holes 190. The mask layer is used as an etch mask for forming the release holes 190. In this embodiment, the material of the mask layer includes a photoresist, and the mask layer can be formed by a photolithography process such as coating, exposure, and development. In this embodiment, a dry etching process is adopted, for example: an anisotropic dry etching process etches the piezoelectric acoustic resonance stack 550 and the second planarization layer 160 on the sacrificial layer 130 to form the release holes 190.

Referring to fig. 12, including fig. 12a and 12b, fig. 12a is a sectional view based on fig. 11a, and fig. 12b is a sectional view based on fig. 11b, the sacrificial layer 130 (shown in fig. 11) is removed through the release hole 190 to form a cavity 200.

The cavity 200 is a back cavity in the resonator. Through the cavity 200, the bottom electrode 140 can be in contact with air, so that the leaked sound waves are totally reflected at the junction of the bottom electrode 140 and the air, the electromechanical coupling coefficient and the Q value of the resonator are further improved, and the performance of the bulk acoustic wave resonator is correspondingly improved.

In this embodiment, the material of the sacrificial layer 130 is amorphous carbon, and therefore, the ashing process is used to remove the sacrificial layer 130. The ashing process can release the sacrificial layer 130 under a gas phase condition, which is beneficial to reducing the residue of the sacrificial layer 130 and easily removing the sacrificial layer 130, and the ashing process has a high etching selectivity for the materials of the sacrificial layer 130 and the piezoelectric acoustic resonance stack 550, so that the sacrificial layer 130 can be removed cleanly while the influence on the piezoelectric acoustic resonance stack 550 is reduced. And the cost of the ashing process is low.

Compared with the scheme of forming the cavity in a bonding mode, the cavity 200 is directly formed in the substrate 100 in the embodiment without consuming an additional bearing substrate, which is beneficial to reducing the process cost and realizing the mass production of the bulk acoustic wave resonator; in addition, by forming the piezoelectric acoustic resonance stack 550 directly on the substrate 100, it is advantageous to realize integration of the signal processing circuit with the piezoelectric acoustic resonance stack 550, thereby contributing to reduction in reliability of the bulk acoustic wave resonator. For example, the substrate 100 has a signal processing circuit therein, and the film layers in the bulk acoustic wave resonator are formed by a semiconductor thin film covering process, so that the film layers have good bondability, which is beneficial to improving the reliability of the resonator.

In this embodiment, the gas used in the ashing process includes oxygen, and the oxygen reacts with the amorphous carbon to form carbon dioxide gas, which has less side effects and is beneficial to reducing the influence on the piezoelectric acoustic resonance stack 550 and reducing the probability of generating reaction byproduct residues or sacrificial layer 130 residues in the cavity 200. It should be noted that, by removing the sacrificial layer 130 by using the ashing process, the mask layer can be removed in the step of removing the sacrificial layer 130, which is not only beneficial to simplifying the process steps and improving the process integration degree and process compatibility, but also avoids removing the mask layer by using the wet photoresist removal process, prevents the cavity 200 from being exposed in the environment of wet etching, is further beneficial to reducing the probability of generating etching residues in the cavity 200 and reducing the influence on the cavity 200, and is correspondingly beneficial to improving the reliability of the resonator

In this embodiment, the manufacturing method further includes removing the second sub-planarization layer 160 through the release hole 190, forming an opening (not labeled) between the bottom electrode 140 and the first sub-planarization layer 150, wherein the air medium in the opening is different from the material of the bottom electrode 140, and a mismatched acoustic impedance interface can also be formed, so as to reflect the transverse wave, further prevent the transverse wave from being lost, and further improve the Q value of the bulk acoustic wave resonator.

In this embodiment, the second sub-planarization layer 160 and the sacrificial layer 130 are made of the same material, so the second sub-planarization layer 160 and the sacrificial layer 130 are removed in the same step, and the process is simple.

It should be noted that, a part of the second sub-flat layer 160 is located on the substrate 100 and is surrounded by the substrate 100, the bottom electrode 140, the first sub-flat layer 150 and the piezoelectric layer 170, so that the second sub-flat layer 160 surrounded by the substrate 100, the bottom electrode 140, the first sub-flat layer 150 and the piezoelectric layer 170 is remained in the process of removing the second sub-flat layer 160 through the release hole 190. In other embodiments, when the materials of the second sub-planarization layer and the sacrificial layer are different, different processes may be used to remove the second sub-planarization layer and the sacrificial layer, respectively. In other embodiments, when the materials of the second sub-planarization layer and the sacrificial layer are different, the second planarization layer may not be removed.

Fig. 13 to 15 are schematic structural diagrams corresponding to respective steps in another embodiment of the method for manufacturing a resonator according to the present invention.

The same points of the embodiments of the present invention as those of the previous embodiments are not described herein again, and the embodiments of the present invention are different from the previous embodiments in that: the planarization layer 350 is formed in the same step. The planarization layer 350 is formed in the same step, thereby reducing the complexity of the process of forming the planarization layer 350.

Referring to fig. 13, including fig. 13a and fig. 13b, fig. 13a is a cross-sectional view taken along a first direction, fig. 13b is a cross-sectional view taken along a second direction, the first direction and the second direction are perpendicular, after forming the sacrificial layer 330 in the groove (not labeled), the bottom electrode 340 on the sacrificial layer 330 is formed, a part of the boundary of the bottom electrode 340 is located above the groove and extends to the substrate 100 at the periphery of the groove, the flat layer 350 is formed on the substrate 100 exposed by the bottom electrode 340 and contacts with the sidewall of the bottom electrode 340, and the top surface of the flat layer 350 is flush with the top surface of the bottom electrode 340.

As an example, after forming the bottom electrode 340 on the sacrificial layer 330 and extending to cover the portion of the substrate 100 at the periphery of the groove, the planarization layer 350 is formed in the exposed area of the bottom electrode 340. In this embodiment, the bottom electrode 340 is formed by deposition and etching of the corresponding material. The planarization layer 350 may be formed through a metal lift-off process after the bottom electrode 340 is formed, or the planarization layer 350 may be formed through deposition and planarization processes of respective materials after the bottom electrode 340 is formed. Wherein, an appropriate forming process is selected according to the material of the planarization layer 350.

In this embodiment, the planarization layer 350 is made of an insulating material, which can prevent the existence of upper and lower opposite conductive layers at the periphery of the effective resonance area, thereby preventing the generation of a parasitic resonance effect and further improving the performance of the resonator. The material of the planarization layer 350 includes one or more of silicon oxide, silicon nitride, carbon-containing compound, and germanium, wherein the carbon atom percentage content in the carbon-containing compound is greater than 50%. Accordingly, the planarization layer 350 is formed through deposition and planarization processes of the respective materials.

It should be noted that after depositing the corresponding material, before performing the planarization process, the material on the top of the bottom electrode 340 may be etched to remove most of the material, thereby reducing the process difficulty of the planarization process, facilitating the improvement of the dishing problem, and further improving the top surface planarity of the planarization layer. In other embodiments, the bottom electrode may also be formed in the area exposed by the planarization layer after the planarization layer is formed.

In this embodiment, the materials of the planarization layer 350 and the sacrificial layer 330 are different, so that the loss of the planarization layer 350 due to the subsequent process of removing the sacrificial layer 330 is reduced, and the planarization layer 350 can support the piezoelectric acoustic resonance stack.

For a detailed description of the top surface of the planarization layer 350 and the bottom electrode 340, reference may be made to the corresponding description of the foregoing embodiments, and further description is omitted here.

Referring to fig. 14, including fig. 14a and 14b, fig. 14a is a sectional view based on fig. 13a, and fig. 14b is a sectional view based on fig. 13b, a piezoelectric layer 370 covering the bottom electrode 340 and the planarization layer 350 is formed; a top electrode 380 is formed on the piezoelectric layer 370 and a piezoelectric acoustic resonance stack (not labeled) includes the bottom electrode 340, the top electrode 380, and the piezoelectric layer 370. For a detailed description of the piezoelectric layer 370 and the top electrode 380, reference may be made to the corresponding description of the foregoing embodiments, which are not repeated herein.

Referring to fig. 15, including fig. 15a and 15b, fig. 15a is a sectional view based on fig. 14a, and fig. 15b is a sectional view based on fig. 14b, a release hole 390 is formed through the piezoelectric acoustic resonance stack (not labeled), and the sacrificial layer 330 (shown in fig. 14) is removed through the release hole to form a cavity 400.

In this embodiment, the material of the planarization layer 350 is different from that of the sacrificial layer 330, so that the planarization layer 350 exposed by the release hole 390 is still retained. For a detailed description of the release hole 390 and the cavity 400, reference may be made to the corresponding description of the previous embodiments, and further description is omitted here.

For a specific description of the manufacturing method in this embodiment, reference may be made to the corresponding description in the foregoing embodiments, and this embodiment is not repeated herein.

Correspondingly, the embodiment of the invention also provides the bulk acoustic wave resonator. With continued reference to fig. 12, a schematic structural diagram of an embodiment of the bulk acoustic wave resonator of the present invention is shown. Wherein fig. 12 includes fig. 12a and 12b, fig. 12a is a sectional view taken along a first direction, and fig. 12b is a sectional view taken along a second direction, the first direction and the second direction being perpendicular.

The bulk acoustic wave resonator includes: a substrate 100, the substrate 100 having a cavity 200 therein; a piezoelectric acoustic resonance stack 550 located on the substrate 100, the piezoelectric acoustic resonance stack 550 including a bottom electrode 140 partially bounded on the cavity 200 and partially extending outside the cavity 200, a piezoelectric layer 170 located on the bottom electrode 140 and having an end portion extending flat on the bottom electrode 140, and a top electrode 180 located on an upper surface of the piezoelectric layer 170; a planarization layer 500 (shown in FIG. 11) in the same layer as the bottom electrode 140, the planarization layer 500 having a top surface flush with the top surface of the bottom electrode 500 and a gap 155 (shown in FIG. 6) with the bottom electrode 500; a release hole 190 extending through the piezoelectric acoustic resonance stack 550 and communicating with the cavity 200.

The piezoelectric layer 170 extends smoothly at the end of the bottom electrode 140, the piezoelectric layer 170 does not cover the sidewall of the bottom electrode 140, at the junction of the piezoelectric layer 170 and the bottom electrode 140, the piezoelectric layer 170 can be kept smooth and can have a better lattice orientation, so that the performance of the resonator can be improved, and the problem of sudden change of the boundary structure caused by bending of the piezoelectric layer 170 at the end of the bottom electrode 140 can be avoided, and accordingly, the problem of boundary disturbance of sound waves can be avoided, so that the boundary standing waves and the noise waves can be eliminated, and the quality factor of the resonator can be improved. In this embodiment, the bulk acoustic wave resonator is a film bulk acoustic wave resonator.

In this embodiment, the substrate 100 is a wafer-level substrate 100, and the substrate 100 is formed based on a CMOS process. The substrate 100 includes an active resonance region and an inactive region. The area over the cavity 200 where the top electrode 180 overlaps the bottom electrode 140 is the active resonance area and the remaining area is the inactive area. The shape of the effective resonance region may be any shape, such as a square, a circle, a pentagon, a hexagon, or an irregular polygon.

Through the cavity 200, the bottom electrode 140 can be in contact with air, so that the leaked sound waves are totally reflected at the junction of the bottom electrode 140 and the air, the electromechanical coupling coefficient and the Q value of the bulk acoustic wave resonator are further improved, and the performance of the bulk acoustic wave resonator is correspondingly improved. As an example, the longitudinal cross-sectional shape of the cavity 200 is an inverted trapezoid, i.e. the cavity 200 comprises four sidewalls, and the top dimension of the cavity 200 is larger than the bottom dimension. The top dimension of the cavity 200 is larger than the bottom dimension, which facilitates total reflection of the leaked acoustic waves at the interface of the bottom electrode 140 and the air.

The number of cavities 200 is at least one. In the present embodiment, the substrate 100 includes a plurality of resonator unit regions (not labeled), and each resonator unit region has one cavity 200 formed therein, so that the number of the cavities 200 is plural, so as to form a bulk acoustic wave resonator on the substrate 100, thereby realizing mass production. For convenience of illustration, only one resonator element region is illustrated in the figure.

A portion of the boundary of the bottom electrode 140 is located above the cavity 200 and on the etch stop layer 120 that extends partially to the periphery of the cavity 200. In this embodiment, the substrate 100 includes a plurality of resonator unit regions (not labeled), and each resonator unit region has a cavity 200 formed therein, so that the number of the bottom electrodes 140 is correspondingly plural, the plurality of bottom electrodes 140 are separately disposed, and the bottom electrodes 140 and the resonator unit regions correspond to each other one by one.

The material of the bottom electrode 140 may be a conductive material such as a metal, a metal silicide, a metal nitride, a metal oxide, or conductive carbon. In this embodiment, the bottom electrode 140 is made of Mo.

In this embodiment, a part of the boundary of the bottom electrode 140 is located above the cavity 200, the cavity medium is different from the medium of the stacked structure, the acoustic impedance is different, and the sound wave is reflected at the interface where the acoustic impedance is not matched, so that the effect of reflecting the sound wave is realized to maintain the oscillation. The piezoelectric acoustic resonance stack 550 in the inactive region is susceptible to parasitic capacitance, and the influence of the parasitic capacitance on the piezoelectric acoustic resonance stack 550 in the active resonance region is reduced by locating a portion of the boundary of the bottom electrode 140 above the cavity 200 to isolate the active resonance region from the inactive region.

The material of the piezoelectric layer 170 may be a piezoelectric crystal, a piezoelectric ceramic, a piezoelectric polymer, or the like. The piezoelectric crystal can be aluminum nitride, lead zirconate titanate, quartz crystal, lithium gallate, lithium germanate, titanium germanate, lithium niobate or lithium tantalate, and the piezoelectric polymer can be polyvinylidene fluoride, vinylidene fluoride-trifluoroethylene copolymer, nylon-11 or vinylidene cyanide-vinyl acetate alternating copolymer, and the like. In this embodiment, the piezoelectric layer 170 is made of aluminum nitride.

The material of the top electrode 180 may be a metal, a metal silicide, a metal nitride, a metal oxide, or a conductive material such as conductive carbon. In this embodiment, the material of the top electrode 180 is Mo.

In this embodiment, a portion of the boundary of the top electrode 180 is located on the cavity 200, and a portion of the boundary extends to the periphery of the cavity 200 on the substrate 100. Therefore, in forming the release hole 190 penetrating through the piezoelectric acoustic resonance stack 550, the release hole 190 may not penetrate through the three layers of the top electrode 180, the piezoelectric layer 170, and the bottom electrode 160, thereby contributing to reducing the difficulty of the process of forming the release hole 190. In this embodiment, the top electrode 180 and the bottom electrode 170 of the inactive region are offset from each other to reduce the parasitic capacitance generated by the piezoelectric acoustic resonance stack 550 in the inactive region.

The flat layer 500 is located on the same layer as the bottom electrode 140, and the top surface of the flat layer 500 is flush with the top surface of the bottom electrode 140. in the manufacturing process of the bulk acoustic wave resonator, the flat layer 500 is used to provide a flat surface for the formation of the piezoelectric layer 170, accordingly, the piezoelectric layer does not cover the sidewall of the bottom electrode 140, and the piezoelectric layer 170 can be kept flat at the interface between the piezoelectric layer 170 and the bottom electrode 140.

In this embodiment, the planarization layer 500 is made of an insulating material, which can prevent the existence of upper and lower opposite conductive layers at the periphery of the effective resonance area, thereby preventing the generation of a parasitic resonance effect and further improving the performance of the resonator. Specifically, the material of the planarization layer 500 includes one or more of silicon oxide, silicon nitride, carbon-containing compound, and germanium, wherein the carbon atom percentage content in the carbon-containing compound is greater than 50%. As an example, the material of the planarization layer 500 is silicon nitride. The silicon nitride has higher dielectric constant and better insulating effect. In other embodiments, the material of the planarization layer may also be silicon oxide.

A gap 155 is formed between the flat layer 500 and the bottom electrode 140, and an air medium in the gap 155 is different from the material of the bottom electrode 140, so that a mismatched acoustic impedance interface can be formed, transverse waves are reflected, and the Q value of the bulk acoustic wave resonator is improved.

In this embodiment, the planarization layer 500 includes: a first sub-planarization layer 150 on the substrate 100 at the periphery of the cavity 200, the first sub-planarization layer 150 and the bottom electrode 140 enclosing a gap 155; and a second sub-planarization layer 160 located in an area enclosed by the piezoelectric layer 170, the bottom electrode 140 layer, the first sub-planarization layer 150 and the substrate 100. That is, the second sub planarization layer 160 is not present in the region communicating with the release hole 190. In the manufacturing process of the bulk acoustic wave resonator, the second sub planarization layer 160 is formed in the gap 155, and in the process of removing the sacrificial layer in the cavity 200 through the release hole 190, the second sub planarization layer 160 is removed through the release hole 190. Therefore, the first sub-planarization layer 150 is formed first to cover most of the area, which is beneficial to improve the recess problem of the planarization process when forming the second sub-planarization layer 160, so as to improve the top surface planarization of the second sub-planarization layer 160, and accordingly improve the top surface planarization of the planarization layer 500, thereby improving the planarization of the piezoelectric layer 170.

In this embodiment, the first sub-planarization layer 150 is made of an insulating material, which can prevent the existence of upper and lower opposite conductive layers at the periphery of the effective resonance area, thereby preventing the generation of parasitic resonance effect. Specifically, the material of the first sub-planarization layer 150 includes one or more of silicon oxide, silicon nitride, carbon-containing compound, and germanium, wherein the carbon atom percentage content in the carbon-containing compound is greater than 50%. As an example, the material of the first sub-planarization layer 150 is silicon nitride. In other embodiments, the material of the first planarization layer may also be silicon oxide. In other embodiments, the material of the bottom electrode and the material of the first sub-planarization layer may be the same, so that the bottom electrode and the first sub-planarization layer can be formed in the same step, thereby simplifying the process steps.

In this embodiment, the second sub-planarization layer 160 is made of an insulating material, which can prevent the existence of upper and lower opposite conductive layers at the periphery of the effective resonance region, thereby preventing the generation of parasitic resonance effect. Specifically, the material of the second sub-planarization layer 160 includes one or more of silicon oxide, silicon nitride, carbon-containing compound, and germanium, wherein the carbon atom percentage content in the carbon-containing compound is greater than 50%. By selecting the above materials, when the second sub planarization layer 160 is removed through the release hole 190, the influence on the bottom electrode 140 is small. In this embodiment, the second sub-planarization layer 160, the sacrificial layer 130 and the first sub-planarization layer 150 are made of the same material, so that the second sub-planarization layer 160 and the sacrificial layer 130 can be removed in the same process, thereby simplifying the process complexity and reducing the damage to the first sub-planarization layer 150. Accordingly, the material of the second sub-planarization layer 160 is amorphous carbon. In other embodiments, the materials of the second sub-planarization layer and the sacrificial layer may also be different.

In this embodiment, the gap 155 extends along the boundary of the effective resonance region, thereby enabling the sidewall of the bottom electrode 140 to be in contact with the air medium. As an example, the planar layer 500 encloses a closed annular gap 155 with a portion of the boundary of the top electrode 140, i.e., the planar layer 500 surrounds the top electrode 140 with the gap 155 with the top electrode 140. In other embodiments, the planar layer surrounds a portion of the boundary with the top electrode in a ring shape with a gap. For example, when the shape of the effective resonance region is a pentagon, the flat layer and the four sides of the top electrode enclose a ring shape with a gap.

The width of the gap 155 should not be too small, nor too large. If the width of the gap 155 is too small, it is difficult to fill the material of the second sub planarization layer 160 in the gap 155, which easily results in a low degree of planarization of the top surface of the second sub planarization layer 160, and accordingly it is difficult to improve the planarization of the piezoelectric layer 170; if the width of the gap 155 is too large, the effect of improving the dishing problem is not good when forming the second sub planarization layer 160, which is not good for improving the planarity of the top surface of the second sub planarization layer 160, and thus it is difficult to improve the planarity of the piezoelectric layer 170. For this reason, in the present embodiment, the width of the gap 155 is 1 nm to 100 nm.

In the manufacturing process of the bulk acoustic wave resonator, the sacrificial layer in the cavity 200 is removed through the release holes 190. In this embodiment, the number of the release holes 190 is plural, so that the efficiency of removing the sacrificial layer is improved. In this embodiment, the release holes 190 penetrate through the top electrode 180 or the bottom electrode 170, that is, the release holes 190 penetrate through the piezoelectric acoustic resonance stack 550 located in the inactive region, but do not penetrate through the piezoelectric acoustic resonance stack 550 located in the active resonance region, so that the piezoelectric acoustic resonance stack 550 located in the active resonance region is not etched in the process of forming the release holes 190, which is beneficial to reducing the influence on the piezoelectric acoustic resonance stack 550 located in the active resonance region, and thus beneficial to improving the reliability of the bulk acoustic wave resonator.

Specifically, depending on the formation location of the release hole 190 and the stack structure of the piezoelectric acoustic resonance stack 550 corresponding to the location, the release hole 190 may penetrate the top electrode 180 and the piezoelectric layer 170 and communicate with the cavity 200; alternatively, the release holes 190 extend through the piezoelectric layer 170 and the planarization layer 500 and communicate with the cavity 200; alternatively, the release hole 190 penetrates the top electrode 180, the piezoelectric layer 170, and the planarization layer 500 and communicates with the cavity 200; alternatively, the release holes 190 extend through the piezoelectric layer 170 and communicate with the cavity 200.

In this embodiment, the bulk acoustic wave resonator further includes: and an etch stop layer 120 located between the planarization layer 500 and the substrate 100 and extending to cover the sidewalls and bottom of the cavity 200. The etch stop layer 120 is used to achieve electrical isolation of the substrate 100 and the bottom electrode 140; moreover, the process of forming the bottom electrode 140 includes a deposition process and an etching process which are sequentially performed, the etch stop layer 120 is used to define an etching stop position during the process of forming the bottom electrode 140, so as to reduce damage to the substrate 100, and accordingly, the etch stop layer 120 is also used to protect the substrate 100. In addition, in the manufacturing process of the bulk acoustic wave resonator, the position of the cavity 200 is filled with a sacrificial layer, the process of forming the sacrificial layer includes a planarization process, and the etch stop layer 120 is also used for defining the stop position of the planarization process, so that the surface flatness of the sacrificial layer is favorably improved.

The material of the etch stop layer 120 is an insulating material, so as to electrically isolate the substrate 100 from the bottom electrode, and the material of the etch stop layer 120 includes one or more of silicon oxide, silicon nitride, and silicon oxynitride. In this embodiment, the material of the etch stop layer 120 is silicon oxide, which enables the etch stop layer 120 to also function as a stress buffer.

It should be noted that the thickness of the etch stop layer 120 is not too small, nor too large. If the thickness is too small, the above-mentioned properties of the etch stop layer 120 are difficult to be secured; if the thickness of the film is too large, the flatness of the film is difficult to ensure, and the formation quality of a subsequent film layer is influenced. Therefore, in the present embodiment, the thickness of the etch stop layer 120 is 50 nm to 1000 nm.

The resonator described in this embodiment may be formed by the manufacturing method described in the foregoing embodiment, or may be formed by another manufacturing method. For specific description of the resonator in this embodiment, reference may be made to corresponding description in the foregoing embodiments, and details of this embodiment are not repeated herein.

Correspondingly, the embodiment of the invention also provides another bulk acoustic wave resonator. With continued reference to fig. 15, a schematic structural diagram of an embodiment of the bulk acoustic wave resonator of the present invention is shown. Wherein fig. 15a is a sectional view taken along a first direction, and fig. 15b is a sectional view taken along a second direction, the first direction and the second direction being perpendicular.

The same points of the embodiments of the present invention as those of the previous embodiments are not described herein again, and the embodiments of the present invention are different from the previous embodiments in that: there is no gap between the planar layer 350 and the bottom electrode 340.

Specifically, the bulk acoustic wave resonator includes: a substrate 300, the substrate 300 having a cavity 400 therein; a piezoelectric acoustic resonance stack (not labeled) on the substrate 100, the piezoelectric acoustic resonance stack including a bottom electrode 340 partially bounded on the cavity 400 and partially extending outside the cavity 400, a piezoelectric layer 370 on the bottom electrode 340 and having a flat extension at the end of the bottom electrode 340, and a top electrode 380 on the upper surface of the piezoelectric layer 370; a planarization layer 350, which is located at the same layer as the bottom electrode 340, wherein the top surface of the planarization layer 350 is flush with the top surface of the bottom electrode 340, the planarization layer 350 contacts the bottom electrode 340, and covers the substrate 100 exposed from the bottom electrode 340; a release hole extending through the piezoelectric acoustic resonance stack and communicating with the cavity 400.

In this embodiment, the planarization layer 350 is a unitary structure, that is, the planarization layer is formed in the same step during the manufacturing process of the bulk acoustic wave resonator. Accordingly, the planarization layer 350 of the present embodiment is located on the bottom surface of the piezoelectric layer where the bottom electrode is exposed. The material of the planarization layer 350 is an insulating material, so that a parasitic resonance effect is prevented from being generated at the periphery of the effective resonance region, and the performance of the resonator can be better improved. Specifically, the material of the planarization layer 350 includes one or more of silicon oxide, silicon nitride, carbon-containing compounds, and germanium.

For specific description of the bulk acoustic wave resonator in this embodiment, reference may be made to corresponding description in the foregoing embodiments, and details of this embodiment are not repeated herein.

Correspondingly, the embodiment of the invention also provides a filter, which comprises the bulk acoustic wave resonator provided by the foregoing embodiment. The bulk acoustic wave resonators of the foregoing embodiments have a higher quality factor, which correspondingly improves the performance of the filter.

Correspondingly, the embodiment of the invention also provides electronic equipment, which comprises the filter provided by the embodiment. The filter may be incorporated into various electronic devices. From the foregoing analysis, it can be seen that the performance of the filter is high, which in turn enables a high performance electronic device. The electronic device can be a personal computer, a mobile terminal such as a smart phone, a media player, a navigation device, an electronic game device, a game controller, a tablet computer, a wearable device, an access control prevention electronic system, a POS terminal, a medical device, a flight simulator and the like.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A method of manufacturing a bulk acoustic wave resonator, comprising:

providing a substrate, wherein a groove is formed in the substrate;

filling the groove to form a sacrificial layer positioned in the groove;

forming a bottom electrode on the sacrificial layer, wherein part of the boundary of the bottom electrode is positioned above the groove, and part of the boundary extends to the substrate on the periphery of the groove;

forming a flat layer which is positioned on the substrate exposed by the bottom electrode and is contacted with the side wall of the bottom electrode, wherein the top surface of the flat layer is flush with the top surface of the bottom electrode;

forming a piezoelectric layer overlying the bottom electrode and the planarization layer;

forming a top electrode on the piezoelectric layer, the piezoelectric acoustic resonance stack comprising a bottom electrode, the piezoelectric layer, and the top electrode;

forming a release hole through the piezoelectric acoustic resonance stack;

and removing the sacrificial layer through the release hole to form a cavity.

2. The manufacturing method according to claim 1, wherein the method of forming the planarization layer includes: forming a first sub-flat layer on the substrate at the periphery of the groove, wherein a gap is formed by the first sub-flat layer and the bottom electrode, and the top surface of the first sub-flat layer is flush with the top surface of the bottom electrode;

and forming a second sub-flat layer in the gap, wherein the top surface of the second sub-flat layer is flush with the top surface of the bottom electrode.

3. The manufacturing method according to claim 2, further comprising: removing the second sub-planarization layer through the release hole.

4. The manufacturing method according to claim 3, wherein the second sub-planarization layer and the sacrificial layer are made of the same material.

5. The manufacturing method according to claim 2, wherein the material of the bottom electrode is the same as the material of the first sub-planarization layer, and in the same step, the bottom electrode and the first sub-planarization layer are formed;

or, the material of the first sub-flat layer is an insulating material.

6. The method of manufacturing of claim 1, wherein a portion of the boundary of the top electrode is located on the recess and extends partially onto the substrate at the periphery of the recess.

7. The manufacturing method according to claim 1, wherein after the formation of the planarization layer, a bottom electrode is formed in a region where the planarization layer is exposed;

or after forming a bottom electrode which is positioned on the sacrificial layer and extends to cover part of the substrate at the periphery of the groove, forming a flat layer in the exposed area of the bottom electrode.

8. The manufacturing method according to claim 1, wherein the planarization layer is formed by a metal lift-off process after the bottom electrode is formed, or by deposition and planarization treatment of a corresponding material after the bottom electrode is formed.

9. The method of manufacturing of claim 1, wherein the top electrode and the bottom electrode of the inactive area are staggered with respect to each other.

10. The method of manufacturing of claim 2, wherein the gap extends along a boundary of the effective resonance region.

11. The method of manufacturing of claim 10, wherein the first sub-planar layer encloses a closed annular gap with a portion of a boundary of the top electrode; alternatively, the first sub-flat layer and a part of the boundary of the top electrode enclose a ring shape with a gap.

12. The manufacturing method according to claim 1, wherein after forming the groove in the substrate and before forming the sacrificial layer located in the groove, the manufacturing method further comprises: and forming an etching stop layer on the substrate, wherein the etching stop layer also conformally covers the bottom and the side wall of the groove.

13. The method of claim 1, wherein the material of the sacrificial layer comprises one or more of silicon oxide, carbon, a carbon-containing compound, and germanium, wherein the carbon atom percent content of the carbon-containing compound is greater than 50%.

14. The method of claim 1, wherein the material of the planarization layer comprises one or more of silicon oxide, silicon nitride, carbon, a carbon-containing compound, and germanium, wherein the carbon atom percent content of the carbon-containing compound is greater than 50%.

15. The method of manufacturing of claim 2, wherein the gap has a width of 1 nm to 100 nm.

16. A bulk acoustic wave resonator, comprising:

a substrate having a cavity therein;

a piezoelectric acoustic resonance stack located on the substrate, the piezoelectric acoustic resonance stack including a bottom electrode partially bounded on the cavity and extending partially outside the cavity, a piezoelectric layer located on the bottom electrode and having a flat extension at an end of the bottom electrode, and a top electrode located on an upper surface of the piezoelectric layer;

the flat layer and the bottom electrode are positioned on the same layer, the top surface of the flat layer is flush with the top surface of the bottom electrode, and a gap is formed between the flat layer and the bottom electrode;

a release aperture extending through the piezoelectric acoustic resonance stack and communicating with the cavity.

17. The bulk acoustic wave resonator according to claim 16, wherein a portion of the boundary of the top electrode is located on the cavity and extends partially onto the substrate at the periphery of the cavity.

18. The bulk acoustic wave resonator according to claim 16, wherein the top electrode and the bottom electrode of the inactive region are staggered with respect to each other.

19. The bulk acoustic wave resonator according to claim 16, wherein the gap extends along a boundary of the effective resonance region.

20. The bulk acoustic wave resonator according to claim 19, wherein the planar layer encloses a closed annular gap with a portion of a boundary of the top electrode; alternatively, the planar layer and a portion of the boundary of the top electrode enclose a ring shape having a gap.

21. The bulk acoustic wave resonator according to claim 16, wherein a region on the cavity where the top electrode overlaps the bottom electrode is an effective resonance region, and the effective resonance region has an irregular polygonal shape.

22. The bulk acoustic wave resonator of claim 16, wherein the material of the planar layer comprises one or more of silicon oxide, silicon nitride, carbon-containing compounds, and germanium, wherein the carbon atomic percent content of the carbon-containing compounds is greater than 50%.

23. The bulk acoustic wave resonator according to claim 16, wherein the width of the gap is 1 nm to 100 nm.

24. The bulk acoustic wave resonator of claim 16, wherein the resonator further comprises: and the etching stop layer is positioned between the flat layer and the substrate and extends to cover the side wall and the bottom of the cavity.

25. The bulk acoustic wave resonator according to claim 24, wherein the etch stop layer has a thickness of 50 nm to 1000 nm.

26. A bulk acoustic wave resonator, comprising:

a substrate having a cavity therein;

the flat layer and the bottom electrode are positioned on the same layer, the top surface of the flat layer is flush with the top surface of the bottom electrode, and the flat layer is in contact with the bottom electrode and covers the substrate exposed by the bottom electrode;

27. A filter comprising a bulk acoustic wave resonator according to any of claims 16 to 25.

28. A filter comprising the bulk acoustic wave resonator of claim 26.

29. An electronic device comprising the filter of claim 27.

30. An electronic device comprising the filter of claim 28.