WO2021248866A1

WO2021248866A1 - Bulk acoustic resonator and manufacturing method therefor, filter and electronic device

Info

Publication number: WO2021248866A1
Application number: PCT/CN2020/137219
Authority: WO
Inventors: 黄河
Original assignee: 中芯集成电路（宁波）有限公司上海分公司
Priority date: 2020-06-09
Filing date: 2020-12-17
Publication date: 2021-12-16
Also published as: CN112117988B; CN112117988A

Abstract

A bulk acoustic resonator and a manufacturing method therefor, a filter and an electronic device. The manufacturing method comprises: providing a substrate (100), a groove (110) being formed in the substrate (100); forming a sacrificial layer (130) located in the groove (110); forming a bottom electrode (140) located on the sacrificial layer (130), part of the boundary of the bottom electrode (140) being located above the groove (110), and part thereof extending onto the substrate (100) on the periphery of the groove (110); forming a planarization layer (500) that is located on the substrate (100) exposed from the bottom electrode (140) and is in contact with the side wall of the bottom electrode (140), the top face of the planarization layer (500) being flush with the top face of the bottom electrode (140); forming a piezoelectric layer (170) that covers the bottom electrode (140) and the planarization layer (500); forming a top electrode (180) on the piezoelectric layer (170), a piezoelectric acoustic resonance lamination layer (550) comprising the bottom electrode (140), the piezoelectric layer (170) and the top electrode (180); forming release holes (190) penetrating through the piezoelectric acoustic resonance lamination layer (550); and removing the sacrificial layer (130) via the release holes (190), so as to form a cavity (200). The bottom electrode (140) and the planarization layer (500) are formed to provide a flat face for the formation of the piezoelectric layer (170), such that the piezoelectric layer (170) can be kept flat, thereby eliminating boundary standing waves and clutters, and thus improving the quality factor of the resonator.

Description

Bulk acoustic wave resonator and its manufacturing method, filter and electronic equipment

Technical field

The embodiments of the present invention relate to the field of semiconductor manufacturing, and in particular, to a bulk acoustic wave resonator, a manufacturing method thereof, a filter, and an electronic device.

Background technique

With the development of wireless communication technology, traditional single-band single-standard equipment can no longer meet the diversified requirements of communication systems. At present, communication systems are becoming more and more multi-frequency bands, which requires communication terminals to be able to accept various frequency bands to meet the requirements of different communication service providers and different regions.

RF (Radio Frequency) filters are usually used to pass or block specific frequencies or frequency bands in RF signals. In order to meet the development needs of wireless communication technology, RF filters used in communication terminals are required to achieve multi-band and multi-standard communication technology requirements. At the same time, RF filters in communication terminals are required to continue to develop in the direction of miniaturization and integration. Each frequency band uses one or more RF filters.

The most important indicators of RF filters include quality factor Q and insertion loss. As the frequency difference between different frequency bands becomes smaller and smaller, the RF filter needs to be very selective, allowing signals in the frequency band to pass and blocking signals outside the frequency band. The larger the Q value, the narrower the passband bandwidth of the RF filter can be achieved, thereby achieving better selectivity.

technical problem

The problem solved by the embodiments of the present invention is to provide a bulk acoustic wave vibrator, a manufacturing method thereof, a filter, and an electronic device, so as to improve the quality factor of the bulk acoustic wave resonator.

Technical solutions

In order to solve the above-mentioned problems, an embodiment of the present invention provides a method for manufacturing a bulk acoustic wave resonator, including: providing a substrate with a groove formed in the substrate; filling the groove to form a bulk acoustic wave resonator A sacrificial layer; forming a bottom electrode located on the sacrificial layer, a part of the boundary of the bottom electrode is located above the groove, and part of the boundary of the bottom electrode extends to the substrate on the periphery of the groove; forming a bottom electrode exposed A flat layer on the substrate and in contact with the sidewall of the bottom electrode, the top surface of the flat layer and the top surface of the bottom electrode are flush; forming a piezoelectric layer covering the bottom electrode and the flat layer Layer; forming a top electrode on the piezoelectric layer, the piezoelectric acoustic resonance stack includes a bottom electrode, a piezoelectric layer and a top electrode; forming a release hole through the acoustic transducer; through the release hole to remove the The sacrificial layer forms a cavity.

Correspondingly, an embodiment of the present invention also provides a bulk acoustic wave resonator, including: a substrate with a cavity therein; a piezoelectric acoustic resonance stack located on the substrate, the piezoelectric acoustic resonance The laminate includes a bottom electrode with a part boundary on the cavity, a bottom electrode partly extending outside the cavity, a piezoelectric layer on the bottom electrode and having a piezoelectric layer extending flatly at the end of the bottom electrode, and a bottom electrode on the bottom electrode. The top electrode on the upper surface of the piezoelectric layer; is located in 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 there is a gap between the bottom electrode; a release hole penetrates The acoustic transducer is in communication with the cavity.

Correspondingly, an embodiment of the present invention also provides another bulk acoustic wave resonator, including: a substrate with a cavity in the substrate; a piezoelectric acoustic resonance stack located on the substrate, and the piezoelectric acoustic resonator The resonant stack includes a bottom electrode with a part boundary on the cavity, a part extending outside the cavity, a piezoelectric layer on the bottom electrode and a piezoelectric layer extending flat on the end of the bottom electrode, and The top electrode on the upper surface of the piezoelectric layer; a flat layer, which is located in the same layer as the bottom electrode, the top surface of the flat layer is flat with the top surface of the bottom electrode, the flat layer is in contact with the bottom electrode, and Covering the exposed substrate of the bottom electrode; a release hole, penetrating the piezoelectric acoustic resonance stack and communicating with the cavity.

Correspondingly, an embodiment of the present invention also provides a filter, including the bulk acoustic wave resonator provided in the first embodiment of the present invention.

Correspondingly, the embodiment of the present invention also provides another filter, including the bulk acoustic wave resonator provided in the second embodiment of the present invention.

Correspondingly, an embodiment of the present invention also provides an electronic device, including the filter provided in the first embodiment of the present invention.

Correspondingly, an embodiment of the present invention also provides another electronic device, including the filter provided in the second embodiment of the present invention.

Beneficial effect

Compared with the prior art, the technical solution of the embodiment of the present invention has the following advantages: in the method for manufacturing a bulk acoustic wave resonator provided by the embodiment of the present invention, after the sacrificial layer is filled in the groove in the substrate, the sacrificial layer is formed Part of the boundary of the bottom electrode is located above the groove and partly extends to the substrate on the periphery of the groove, and forms a flat layer on the substrate exposed by the bottom electrode and in contact with the sidewall of the bottom electrode. The top surface and the top surface of the bottom electrode are flush, which provides a flat surface 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 will not cover the sidewall of the bottom electrode. At the junction of the piezoelectric layer and the bottom electrode, the piezoelectric layer can be kept flat and can have a better lattice orientation, which can improve the performance of the resonator, and can avoid the piezoelectric layer at the end of the bottom electrode. The sudden change of the boundary structure caused by the bending can avoid the boundary disturbance problem of the acoustic wave, thereby helping to eliminate the boundary standing waves and clutter, thereby improving the quality factor of the resonator.

In an alternative solution, the method for forming the flat layer includes: forming a first sub-flat layer on the substrate on the outer periphery of the groove, the first sub-flat layer and the bottom electrode enclose a gap, the top surface and the bottom electrode of the first sub-flat layer The top surface is flush with each other; by forming a gap between the bottom electrode and the first sub-flat layer, the bottom electrode is exposed in the gap, which can further prevent the loss of transverse waves, thereby improving the quality factor of the resonator.

In an alternative solution, the material of the first sub-flat layer is an insulating material, which can avoid the existence of upper and lower conductive layers facing the periphery of the effective resonance region, thereby avoiding parasitic resonance effects, and thus can better improve the performance of the resonator.

Description of the drawings

Figures 1 to 2 are schematic diagrams of the structure corresponding to each step in a method for manufacturing a bulk acoustic wave resonator.

3 to 12 are schematic diagrams of the structure corresponding to each step in an embodiment of the method for manufacturing a bulk acoustic wave resonator of the present invention.

13 to 15 are schematic diagrams of the structure corresponding to each step in another embodiment of the method of manufacturing a bulk acoustic wave resonator of the present invention.

Embodiments of the present invention

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 still needs to be improved is analyzed in conjunction with a manufacturing method of the bulk acoustic wave resonator. 1 to 2 are schematic diagrams of the structure corresponding to each step in a method of manufacturing a resonator.

1, a substrate 10 is provided, a sacrificial layer 30 is formed in the substrate 10, and the top surface of the sacrificial layer 30 is exposed from the substrate 10. 2, a piezoelectric acoustic resonance stack (not labeled) is formed on the sacrificial layer 30. The piezoelectric acoustic resonance stack includes a bottom electrode 40, a piezoelectric layer 50 covering the bottom electrode 40, and a top portion of the piezoelectric layer 50.极60。 Electrode 60.

Part of the boundary of the bottom electrode 40 is located above the sacrificial layer 30 and partly extends to the substrate 10 on the periphery of the sacrificial layer 30. Therefore, the piezoelectric layer 50 not only covers the top of the bottom electrode 40, but also covers the sidewalls of the bottom electrode 40. This correspondingly 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), resulting in a sudden change in the boundary structure. The sudden change in the boundary structure is likely to cause boundary disturbances on the sound wave, and then produce boundary stationary Waves and clutter, correspondingly cause the quality factor of the resonator to decrease.

In order to solve the technical problem, the embodiment of the present invention forms a bottom electrode on the sacrificial layer, part of the boundary of the bottom electrode is located above the groove, and partly extends to the substrate on the periphery of the groove, and forms the substrate where the bottom electrode is exposed The top surface of the flat layer and the top surface of the bottom electrode are flush, which provides a flat surface for the formation of the piezoelectric layer, correspondingly, a piezoelectric layer covering the bottom electrode and the flat layer is formed Later, the piezoelectric layer will not cover the sidewall of the bottom electrode. At the junction of the piezoelectric layer and the bottom electrode, the piezoelectric layer can remain flat and have a better lattice orientation, which can improve the performance of the resonator. And it can avoid the boundary structure mutation problem caused by the bending of the piezoelectric layer at the end position of the bottom electrode, which can correspondingly avoid the boundary disturbance problem of the acoustic wave, thereby helping to eliminate the boundary standing wave and clutter, thereby improving the resonator The quality factor.

In order to make the above objectives, features and advantages of the present invention more obvious and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Referring to Figure 3, including Figures 3a and 3b, Figure 3a is a cross-sectional view along a first direction, and Figure 3b is a cross-sectional view along a second direction, the first direction and the second direction are perpendicular to provide a substrate 100, the substrate A groove 110 is formed in 100.

The manufacturing method is used to form bulk acoustic wave resonators, and bulk acoustic wave resonators refer to devices that generate resonant frequencies. Specifically, the bulk acoustic wave resonator is a film bulk acoustic resonator (film bulk acoustic resonator). Acoustic resonator, FBAR), FBAR is mainly composed of a bottom electrode, a top electrode, and a piezoelectric layer located between the two. FBAR has excellent characteristics such as small size, high resonance frequency, high Q value, large power capacity, and good roll-off effect.

The substrate 100 is used to provide a process platform for the manufacture of a 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. By fabricating the bulk acoustic wave resonator on a wafer, the process cost can be reduced and mass production can be realized, which is beneficial to improve the reliability of the bulk acoustic wave resonator and increase the manufacturing efficiency.

The upper part of the substrate 100 is used to form a piezoelectric acoustic resonance stack. The piezoelectric acoustic resonance stack includes a bottom electrode, a piezoelectric layer, and a top electrode stacked sequentially from bottom to top, thereby realizing a full-film processing process and reducing process costs. In this embodiment, the substrate 100 includes an effective resonance area and an ineffective area. Among them, the area on the groove 110 where the top electrode and the bottom electrode overlap is the effective resonance area, and the remaining area is the ineffective area.

After the piezoelectric acoustic resonance laminate is subsequently formed, the groove 110 is used as a cavity. Therefore, the shape, position, and size of the groove 110 determine the shape, position, and size of the subsequent cavity, and accordingly, the groove 110 is formed according to the shape, position, and size of the required cavity. As an example, the longitudinal cross-sectional shape of the groove 110 is an inverted trapezoid, that is, the groove 110 includes four side walls, and the top dimension of the groove 110 is larger than the bottom dimension. The top size of the groove 110 is larger than the bottom size to facilitate subsequent filling and removal of the sacrificial layer, and it is easy for leaked sound waves to achieve total reflection at the interface between the bottom electrode and the air. The number of the groove 110 is at least one.

In this embodiment, the substrate 100 includes a plurality of resonator unit regions (not labeled), and each resonator unit region is formed with a groove 110. Therefore, the number of the grooves 110 is multiple, so that the substrate A plurality of bulk acoustic wave resonators are formed on 100, thereby realizing mass production. Among them, for ease of illustration, only one resonator unit area is shown in FIG. 3.

Continuing to refer to FIG. 3, the manufacturing method further includes: forming an etch stop layer 120 on the substrate 100, and the etch stop layer 120 also conformally covers the bottom and sidewalls of the groove 110.

Subsequently, a bottom electrode is formed on the substrate 100, and the etch stop layer 120 is used to realize electrical isolation between the substrate 100 and the bottom electrode. Moreover, the process of forming the bottom electrode includes a deposition process and an etching process in sequence, and the etch stop layer 120 is used to define a stop position for etching during the process of forming the bottom electrode, thereby reducing damage to the substrate 100. In addition, a sacrificial layer is subsequently formed in the groove 110, and the process of forming the sacrificial layer includes a planarization process. The etch stop layer 120 is also used to define the stop position of the planarization process, thereby helping to improve the surface flatness of the sacrificial layer.

The material of the etch stop layer 120 is an insulating material to realize electrical isolation between the substrate 100 and the bottom electrode. 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 the metal material is subsequently formed on the substrate 100, the etch stop layer 120 can serve as a stress buffer, thereby improving the film quality of the metal material.

In this embodiment, a deposition process is used to form the etch stop layer 120, and the deposition process 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 or too large. If the thickness is too small, the above-mentioned performance of the etch stop layer 120 is difficult to be guaranteed; if the thickness is too large, the flatness of the etch stop layer 120 is difficult to ensure, thereby affecting the quality of the subsequent film formation. For this reason, in this embodiment, the thickness of the etch stop layer 120 is 50 nanometers to 1000 nanometers. For example, the thickness of the etch stop layer 120 is 100 nanometers, 300 nanometers, 500 nanometers, 700 nanometers, or 900 nanometers.

4, including FIGS. 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 to form the sacrificial layer 130 in the groove 110.

The sacrificial layer 130 fills the groove 110 so as to provide a process platform for the subsequent formation of the piezoelectric acoustic resonance stack. Moreover, after the sacrificial layer 130 fills the groove 110, it can provide a flat surface for the subsequent formation of each functional layer, thereby helping to improve the formation quality of each functional layer.

The sacrificial layer 130 will be removed later. The sacrificial layer 130 is made of materials that can be easily removed, 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, carbon-containing compounds, 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, carbon-containing compounds include amorphous carbon.

In this embodiment, the material of the sacrificial layer 130 is amorphous carbon. The cost of amorphous carbon material is low, and it can be removed by an ashing process later. The ashing process does little damage to the piezoelectric acoustic resonance laminate. The oxygen-containing gas used in the ashing process can oxidize the amorphous carbon to carbon dioxide, thereby reducing The reaction by-products are directly excluded from the reaction chamber, which is beneficial to reduce the risk of residual sacrificial layer 130 and the probability of residual reaction by-products in the cavity, which is correspondingly beneficial to improve the reliability of the bulk acoustic wave resonator.

Specifically, the sacrificial layer 130 whose top surface is flush with the top surface of the etch stop layer 120 is formed through the deposition and planarization treatment of the corresponding material (for example, a chemical mechanical polishing process). Wherein, the planarization process takes the top surface of the etching stop layer 120 as a stop position.

Referring to FIG. 5, including FIGS. 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. It is located above the groove 110 (as shown in FIG. 3) and partially extends to the substrate 100 on the periphery of the groove 110.

Specifically, the bottom electrode 140 covers a part of the sacrificial layer 130 and extends to the etch stop layer 120 on the periphery of the groove 110. In this embodiment, the substrate 100 includes a plurality of resonator unit regions (not labeled), and each resonator unit region is formed with a groove 110. Therefore, the number of bottom electrodes 140 is correspondingly multiple, and the number of bottom electrodes The electrodes 140 are arranged separately, and the bottom electrode 140 corresponds to the resonator unit area one to one.

The material of the bottom electrode 140 can 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 bottom electrode 140 is Mo. Specifically, the bottom electrode 140 is formed by sequentially performing a deposition process and an etching process.

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

In the piezoelectric acoustic resonance laminate, the part with the three-layer structure of the bottom electrode 140, the piezoelectric layer and the top electrode located above the cavity serves as the effective functional layer, and the area corresponding to the effective functional layer serves as the effective resonance region, and the remaining The area is invalid. In this embodiment, part of the boundary of the bottom electrode 140 is located above the groove 110. The cavity medium is different from the laminated structure, and the acoustic impedance is different. The acoustic wave will be reflected at the interface where the acoustic impedance does not match, thereby realizing the effect of reflecting the acoustic wave. To maintain the shock. Among them, the piezoelectric acoustic resonance stack in the ineffective region is prone to generate parasitic capacitance. By exposing part of the sacrificial layer 130 of the bottom electrode 140 to isolate the effective resonance region and the ineffective region, the effect of parasitic capacitance on the piezoelectricity in the effective resonance region is reduced. The effect of acoustic resonance stacking.

With reference to FIGS. 6 to 8, a flat layer 500 (as shown in FIG. 8) is formed on the substrate 100 where the bottom electrode 140 is exposed and is in contact with the sidewall of the bottom electrode 140. The top surface of the flat layer 500 and the top surface of the bottom electrode 140 are formed. Face to face.

Subsequently, a piezoelectric layer covering the bottom electrode 140 and the flat layer 500 is formed. The flat layer 500 is used to cover the exposed area of the bottom electrode 140, and the top surface of the flat layer 500 and the top surface of the bottom electrode 140 are flush, which is the formation of the piezoelectric layer Provide a flat surface, and the piezoelectric layer will not cover the sidewall of the bottom electrode 140. At the junction of the piezoelectric layer and the bottom electrode 140, the piezoelectric layer can be kept flat, and can have a better lattice orientation, which can improve The performance of the resonator can avoid the sudden change of the boundary structure caused by the bending of the piezoelectric layer at the end position of the bottom electrode 140, and correspondingly avoid the boundary disturbance problem of the acoustic wave, thereby helping to eliminate the boundary standing wave and clutter. In turn, the quality factor of the bulk acoustic wave resonator is improved.

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

Specifically, referring to Figure 6, including Figures 6a and 6b, Figure 6a is a cross-sectional view based on Figure 5a, and Figure 6b is a cross-sectional view based on Figure 5b, formed on the substrate 100 on the periphery of the groove 110 (shown in Figure 3) The first sub-flat layer 150, the first sub-flat layer 150 and the bottom electrode 140 enclose a gap 155, and the top surface of the first sub-flat layer 150 and the top surface of the bottom electrode 140 are flush.

The gap 155 is used to provide a space for the formation of the second sub-flat layer. When the second sub-planar layer is subsequently formed in the gap 155, the process of forming the second sub-planar layer includes a planarization process. In this embodiment, the first sub-planar layer 150 is first formed to cover most of the area, which is beneficial to the formation of the second sub-planar layer. In the case of two sub-flat layers, the problem of dishing in the planarization process is improved, thereby helping to improve the flatness of the top surface of the second sub-flat layer, and correspondingly improve the flatness of the top surface of the flat layer, thereby improving the subsequent piezoelectric layer's flatness. Flatness.

In this embodiment, the gap 155 extends along the boundary of the effective resonance region. After subsequent formation of the release hole penetrating the piezoelectric acoustic resonance stack, the second sub-flat layer will be removed through the release hole, thereby forming an opening (not labeled) between the bottom electrode 140 and the first sub-flat layer 150, so that the bottom electrode 140 is exposed to the opening. The air medium in the opening is different from the bottom electrode 140. It can also form a mismatched acoustic impedance interface to reflect the transverse wave to further prevent the loss of the transverse wave, thereby improving the quality factor (Q value) of the bulk acoustic wave resonator. ). Therefore, by extending the gap 155 along the boundary of the effective resonance region, the sidewall of the bottom electrode 140 can be in contact with the air medium.

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

The width of the gap 155 should not be too small or too large. If the width of the gap 155 is too small, it will be difficult to fill the gap 155 with the material of the second sub-flat layer, which will easily lead to the low flatness of the top surface of the second sub-flat layer, and accordingly it is difficult to improve the flatness of the piezoelectric layer; If the width of the gap 155 is too large, when the second sub-flat layer is subsequently formed, the effect of improving the recession problem is not good, which is not conducive to improving the flatness of the top surface of the second sub-flat layer, thereby making it difficult to improve the flatness of the piezoelectric layer . In this embodiment, the width of the gap 155 is 1 nanometer to 100 nanometers. For example, the width of the gap 155 is 10 nanometers, 30 nanometers, 50 nanometers, 70 nanometers, or 90 nanometers.

In this embodiment, the first sub-flat layer 150 is made of insulating material, which can avoid the presence of upper and lower conductive layers at the periphery of the effective resonance region, thereby avoiding parasitic resonance effects. Specifically, the material of the first sub-planar layer 150 includes one or more of silicon oxide, silicon nitride, carbon, carbon-containing compounds, and germanium, wherein the percentage of carbon atoms in the carbon-containing compound is greater than 50%. %. As an example, the material of the first sub-planar layer 150 is silicon nitride. Silicon nitride has a high dielectric constant and a good insulating effect. Moreover, silicon nitride has a high density. When the second sub-planar layer is subsequently removed through the release hole, the first sub-planar layer 150 is damaged. The probability is low. In other embodiments, the material of the first flat layer may also be silicon oxide. Therefore, in this embodiment, the step of forming the first sub-flat layer 150 includes: forming a first sub-flat film that conformally covers the bottom electrode 140 and the exposed substrate 100 and the sacrificial layer of the bottom electrode 140. Layer 130; the first sub-flat film is patterned to form the first sub-flat layer 15. Specifically, a dry etching process (for example, an anisotropic dry etching process) is used to pattern the first sub-flat film. The anisotropic dry etching process has anisotropic etching characteristics, which is beneficial to improve the sidewall topography quality and dimensional accuracy of the first sub-flat layer 150.

In other embodiments, the material of the first sub-planar layer may also be a metal material. Correspondingly, after the bottom electrode is formed, the first sub-planar layer may also be formed by a metal liftoff process. By adopting the metal stripping process, the metal material does not need to be etched, thereby avoiding the problem of the bottom electrode 140 being damaged by etching, and thereby ensuring the quality of the bottom electrode 140.

In this embodiment, the bottom electrode 140 is formed first, and then the first sub-planar layer 150 is formed. In other embodiments, the first sub-planar layer may be formed first, and then the bottom electrode may be formed. Correspondingly, in order to improve the formation quality of the bottom electrode and prevent the formation of the bottom electrode in a region where the bottom electrode is not required to be formed, a metal liftoff process is used to form the bottom electrode, thereby improving the quality of the bottom electrode. In other embodiments, in order to simplify the process steps, the material of the bottom electrode is the same as the material of the first sub-flat layer, and in the same step, the bottom electrode and the first sub-flat layer are formed.

With reference to FIGS. 7 to 8, a second sub-flat layer 160 is formed in the gap 155 (as shown in FIG. 6). The top surface of the second sub-flat layer 160 is flush with the top surface of the bottom electrode 140, and the second sub-flat layer 160 And the first sub-flat layer 150 are used to form the flat layer 500 (as shown in FIG. 8).

In this embodiment, the second sub-planar layer 160 covers the sacrificial layer 130 exposed by the bottom electrode 140. Therefore, when the release hole is subsequently formed, the second flat layer 160 can be exposed at the bottom of the release hole. After the second flat layer 160 is released through the release hole, the sacrificial layer 130 can be released continuously, thereby reducing the process difficulty of forming the releasing hole and reducing the formation Process time of the release hole.

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

Specifically, referring to FIG. 7, including FIGS. 7a and 7b, FIG. 7a is a cross-sectional view based on FIG. 6a, and FIG. 7b is a cross-sectional view based on FIG. The first sub-planar layer 150 and the bottom electrode 140 are also covered.

The second sub-flat film 165 in the gap 155 is subsequently reserved as the second sub-flat layer.

In this embodiment, a deposition process is used to form the second sub-flat film 165. Therefore, after the second sub-flat film 165 is formed, the second sub-flat film 165 covers the entire top surface of the first flat layer 150 and the bottom electrode 140. In this embodiment, after the second sub-flat film 165 is formed, the second sub-flat film 165 on both sides of the gap 155 is etched so that the remaining second sub-flat film 165 covers a part of the first sub-flat layer 150 on both sides of the gap 155 And part of the bottom electrode 140. By first removing most of the second sub-flat film 165 on the top surface of the first sub-flat layer 150 and the bottom electrode 140, the process difficulty of the subsequent planarization process is reduced, thereby improving the flatness of the top surface of the second sub-flat layer.

Specifically, a dry etching process (for example, an anisotropic dry etching process) is used to etch the second sub-flat film 165 on both sides of the gap 155. The anisotropic dry etching process is beneficial to reduce the probability of damage to the second sub-flat film 165 in the gap 155. Moreover, the second sub-planar layer 160 is made of an insulating material, and etching of the insulating material has little effect on the bottom electrode 140.

Referring to FIG. 8, including FIGS. 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. The top surface of the first flat layer 150 and the second sub-flat film 165 of the bottom electrode 140, and the top surface of the remaining second sub-flat film 165 in the gap 155 and the top surface of the bottom electrode 140 are flush, and the remaining second sub-flat film 165 As the second sub-flat layer 160.

In this embodiment, a chemical mechanical polishing process is used for planarization. In other embodiments, according to actual conditions, etching may not be performed before the planarization process is performed on the second sub-flat film.

9, including FIGS. 9 a and 9 b, FIG. 9 a is a cross-sectional view based on FIG. 8 a, and FIG. 9 b is a cross-sectional view based on FIG. 8 b, forming a piezoelectric layer 170 covering the bottom electrode 140 and the flat layer 500.

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

The material of the piezoelectric layer 170 may be piezoelectric crystal, piezoelectric ceramic, or piezoelectric polymer. Wherein, the piezoelectric crystal may be aluminum nitride, lead zirconate titanate, quartz crystal, lithium gallate, lithium germanate, titanium germanate, lithium niobate or lithium tantalate, etc., and the piezoelectric polymer may be Polyvinylidene fluoride, vinylidene fluoride-trifluoroethylene copolymer, nylon-11 or vinylidene cyanide-vinyl acetate alternating copolymer, etc. In this embodiment, the material of the piezoelectric layer 170 is aluminum nitride. Aluminum nitride has the advantages of exhibiting a piezoelectric coupling coefficient of approximately 6.5% and exhibiting lower acoustic and dielectric losses, so that the bulk acoustic wave resonator exhibits a passband that matches the specifications required by most telecommunication standards.

Referring to FIG. 10, including FIGS. 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. 550 includes a bottom electrode 140, a top electrode 180, and a 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. The piezoelectric acoustic resonance stack 550 is used to achieve mutual conversion between electrical signals and acoustic signals, thereby making a bulk acoustic wave resonator Filter the signal.

The material of the top electrode 180 can 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 through deposition and etching of corresponding materials.

In this embodiment, the top electrode 180 is formed by deposition and etching of corresponding materials. In this embodiment, part of the boundary of the top electrode 180 is located on the groove 110 (as shown in FIG. 3), and partly extends to the substrate 100 on the periphery of the groove 110. Therefore, the top electrode 180 exposes the partial pressure on the sacrificial layer 130. The electrical layer 170, correspondingly, in the subsequent process of forming the release hole penetrating the piezoelectric acoustic resonance laminate 550, the release hole may not penetrate the three layers of the top electrode 180, the piezoelectric layer 170 and the bottom electrode 160, which is beneficial to reduce the formation Difficulty of the process of the release hole. In this embodiment, the top electrode 180 and the bottom electrode 170 of the ineffective region are staggered from each other, thereby reducing the parasitic capacitance generated by the piezoelectric acoustic resonance stack in the ineffective region, thereby improving the parasitic resonance effect.

Referring to FIG. 11, including FIGS. 11a and 11b, FIG. 11a is a cross-sectional view based on FIG. 10a, and FIG. 11b is a cross-sectional view based on FIG.

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

In this embodiment, the release hole 190 penetrates the top electrode 180 or the bottom electrode 170, that is, the release hole 190 penetrates the piezoelectric acoustic resonance laminate 550 located in the invalid region, but does not penetrate the piezoelectric acoustic resonance laminate in the effective resonance region. 550. Therefore, in the process of forming the release hole 190, the piezoelectric acoustic resonance laminate 550 in the effective resonance area is not etched, which is beneficial to reduce the influence on the piezoelectric acoustic resonance laminate 550 located in the effective resonance area. It is beneficial to improve the performance of the bulk acoustic wave resonator.

Specifically, according to the formation position of the release hole 190 and the laminated structure of the piezoelectric acoustic resonance laminate 550 corresponding to the position, the release hole 190 may penetrate the top electrode 180 and the piezoelectric layer 170 and expose a portion of the flat layer 500 Top; or, the release hole 190 penetrates the piezoelectric layer 170 and the flat layer 500 and exposes part of the top of the sacrificial layer 130; or, the release hole 190 penetrates the top electrode 180, the piezoelectric layer 170 and the flat layer 500 and exposes the part of the sacrificial layer 130 top. As an example, the release hole 190 penetrates the top electrode 180, the piezoelectric layer 170, and the second sub-flat layer 160 and exposes a part of the top of the sacrificial layer 130. The second sub-planar layer 160 will be removed later. Therefore, the release hole 190 penetrates through the second sub-planar layer 160 so that the second sub-planar layer 160 and the sacrificial layer 130 can be removed at the same time, thereby improving the manufacturing efficiency. In other embodiments, part of the release hole penetrates the second sub-flat layer, and the bottom of the remaining release hole exposes the second sub-flat layer.

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

Referring to FIG. 12, including FIGS. 12a and 12b, FIG. 12a is a cross-sectional view based on FIG. 11a, and FIG. 12b is a cross-sectional view based on FIG. .

The cavity 200 is the back cavity in the resonator. Through the cavity 200, the bottom electrode 140 can be in contact with the air, so that the leaked sound waves are totally reflected at the interface between the bottom electrode 140 and the air, thereby increasing the electromechanical coupling coefficient and Q value of the resonator, and correspondingly improving the bulk acoustic wave resonator Performance.

In this embodiment, the material of the sacrificial layer 130 is amorphous carbon, therefore, the sacrificial layer 130 is removed by an ashing process. The ashing process can release the sacrificial layer 130 under gas phase conditions, which is beneficial to reduce the residue of the sacrificial layer 130, and is easy to remove the sacrificial layer 130. The ashing process affects the sacrificial layer 130 and the piezoelectric acoustic resonance stack 550. The choice of material for etching is relatively high, so that the sacrificial layer 130 can be removed cleanly while reducing the impact on the piezoelectric acoustic resonance laminate 550. And the cost of the ashing process is lower.

Compared with the solution of forming the cavity by bonding, this embodiment directly forms the cavity 200 in the substrate 100 without consuming an additional carrier substrate, which is beneficial to reduce the process cost and realize the mass production of the bulk acoustic wave resonator. In addition, by directly forming the piezoelectric acoustic resonant laminate 550 on the substrate 100, it is beneficial to realize the integration of the signal processing circuit and the piezoelectric acoustic resonant laminate 550, thereby helping to reduce the reliability of the bulk acoustic wave resonator. For example, the substrate 100 has a signal processing circuit, and each film layer in the bulk acoustic wave resonator is formed by a semiconductor film covering process, and the bonding between the film layers is better, which is beneficial to improve the reliability of the resonator.

In this embodiment, the gas used in the ashing process includes oxygen, which reacts with amorphous carbon to form carbon dioxide gas. A probability of residual reaction by-products or residual sacrificial layer 130 in the cavity 200 is generated. It should be noted that by using the ashing process to remove the sacrificial layer 130, the mask layer can be removed in the step of removing the sacrificial layer 130, which not only helps simplify the process steps, improve process integration and process compatibility, Moreover, it also avoids the process of wet stripping to remove the mask layer, preventing the cavity 200 from being exposed to the wet etching environment, thereby helping to reduce the probability of etching residues in the cavity 200 and reduce The influence on the cavity 200 is correspondingly beneficial to improve the reliability of the resonator.

In this embodiment, the manufacturing method further includes removing the second sub-flat layer 160 through the release hole 190, forming an opening (not labeled) between the bottom electrode 140 and the first sub-flat layer 150, and the air medium in the opening and the bottom electrode 140 Different materials can also form a mismatched acoustic impedance interface to reflect the transverse wave to further prevent the loss of the transverse wave, thereby increasing the Q value of the bulk acoustic wave resonator.

In this embodiment, the materials of the second sub-planar layer 160 and the sacrificial layer 130 are the same. Therefore, the second sub-planar layer 160 and the sacrificial layer 130 are removed in the same step, and the process is simple.

It should be noted that 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. Therefore, the second sub-flat layer 160 is removed through the release hole 190. During the process of the sub-flat layer 160, 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 retained. In other embodiments, when the materials of the second sub-planar layer and the sacrificial layer are different, different processes may be used to remove the second sub-planar layer and the sacrificial layer respectively. In other embodiments, when the materials of the second sub-flat layer and the sacrificial layer are different, the second flat layer may not be removed.

13 to 15 are schematic diagrams of the structure corresponding to each step in another embodiment of the manufacturing method of the resonator of the present invention.

The similarities between the embodiment of the present invention and the foregoing embodiment will not be repeated here. The difference between the embodiment of the present invention and the foregoing embodiment is that the flat layer 350 is formed in the same step. The flat layer 350 is formed in the same step, thereby reducing the complexity of the process of forming the flat layer 350.

Referring to Figure 13, including Figures 13a and 13b, Figure 13a is a cross-sectional view along the first direction, Figure 13b is a cross-sectional view along the second direction, the first direction and the second direction are perpendicular to each other and are formed in a groove (not labeled) After the sacrificial layer 330 is formed, a bottom electrode 340 is formed on the sacrificial layer 330. Part of the boundary of the bottom electrode 340 is located above the groove and partly extends to the substrate 100 on the periphery of the groove, forming the substrate 100 where the bottom electrode 340 is exposed. The flat layer 350 above and in contact with the sidewall of the bottom electrode 340 has the top surface of the flat layer 350 flush with the top surface of the bottom electrode 340.

As an example, after the bottom electrode 340 is formed on the sacrificial layer 330 and extends to cover a portion of the substrate 100 on the outer periphery of the groove, a flat layer 350 is formed in a region where the bottom electrode 340 is exposed. In this embodiment, the bottom electrode 340 is formed by deposition and etching of corresponding materials. After the bottom electrode 340 is formed, the flat layer 350 may be formed by a metal lift-off process, or, after the bottom electrode 340 is formed, the flat layer 350 may be formed by deposition and flattening of corresponding materials. Among them, according to the material of the flat layer 350, an appropriate forming process is selected.

In this embodiment, the flat layer 350 is made of an insulating material, which can avoid the presence of upper and lower conductive layers facing the periphery of the effective resonance area, thereby avoiding parasitic resonance effects, and thus can better improve the performance of the resonator. The material of the flat layer 350 includes one or more of silicon oxide, silicon nitride, carbon, carbon-containing compounds, and germanium, wherein the carbon atom percentage content in the carbon-containing compound is greater than 50%. Correspondingly, the planarization layer 350 is formed by the deposition and planarization of the corresponding material.

It should be noted that after the corresponding material is deposited, before the planarization process, the material on the part of the top of the bottom electrode 340 can also be etched to remove most of the material and reduce the process difficulty of the planarization chemical process, thereby helping to improve the recession problem. , Thereby improving the flatness of the top surface of the flat layer. In other embodiments, after forming the flat layer, the bottom electrode may be formed in the exposed area of the flat layer.

In this embodiment, the materials of the flat layer 350 and the sacrificial layer 330 are different, so as to reduce the loss of the flat layer 350 in the subsequent process of removing the sacrificial layer 330, so that the flat layer 350 can play the role of supporting the piezoelectric acoustic resonance stack. .

For the specific description of the top surface of the flat layer 350 and the bottom electrode 340, reference may be made to the corresponding description of the foregoing embodiment, and details are not repeated here.

Referring to Figure 14, including Figures 14a and 14b, Figure 14a is a cross-sectional view based on Figure 13a, and Figure 14b is a cross-sectional view based on Figure 13b, forming a piezoelectric layer 370 covering the bottom electrode 340 and the flat layer 350; on the piezoelectric layer 370 A top electrode 380 is formed, and the piezoelectric acoustic resonance stack (not labeled) includes a bottom electrode 340, a top electrode 380, and a piezoelectric layer 370. For the specific description of the piezoelectric layer 370 and the top electrode 380, reference may be made to the corresponding description of the foregoing embodiment, and details are not repeated here.

Referring to FIG. 15, including FIGS. 15a and 15b, FIG. 15a is a cross-sectional view based on FIG. 14a, and FIG. 15b is a cross-sectional view based on FIG. The sacrificial layer 330 (as shown in FIG. 14) is removed to form a cavity 400.

In this embodiment, the materials of the flat layer 350 and the sacrificial layer 330 are different, and therefore, the flat layer 350 exposed by the release hole 390 is still retained. For the specific description of the release hole 390 and the cavity 400, reference may be made to the corresponding description of the foregoing embodiment, which will not be repeated here.

For the specific description of the manufacturing method in this embodiment, reference may be made to the corresponding description in the foregoing embodiment, and this embodiment will not be repeated here.

Correspondingly, the embodiment of the present invention also provides a bulk acoustic wave resonator. Continuing to refer to FIG. 12, a schematic structural diagram of an embodiment of a bulk acoustic wave resonator of the present invention is shown. Wherein, Fig. 12 includes Fig. 12a and Fig. 12b, Fig. 12a is a cross-sectional view along the first direction, and Fig. 12b is a cross-sectional view along the second direction, the first direction and the second direction are perpendicular.

The bulk acoustic wave resonator includes: a substrate 100 with a cavity 200 in the substrate 100; a piezoelectric acoustic resonance stack 550 located on the substrate 100, and the piezoelectric acoustic resonance stack 550 includes a partial boundary located on the cavity 200 , The bottom electrode 140 that partially extends outside the cavity 200, the piezoelectric layer 170 that is located on the bottom electrode 140 and has a flat extension at the end of the bottom electrode 140, and the top electrode 180 that is located on the upper surface of the piezoelectric layer 170; a flat layer 500 (shown in Figure 11), located on the same layer as the bottom electrode 140, the top surface of the flat layer 500 is flush with the top surface of the bottom electrode 500, and there is a gap 155 between the bottom electrode 500 (shown in Figure 6); release The hole 190 penetrates the piezoelectric acoustic resonance stack 550 and communicates 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 sidewalls 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 flat and smooth. It has a good crystal lattice orientation, which can improve the performance of the resonator, and can avoid the problem of abrupt boundary structure caused by the bending of the piezoelectric layer 170 at the end position of the bottom electrode 140, which can correspondingly avoid the boundary of acoustic waves. Disturbance problem, which helps to eliminate boundary standing waves and clutter, thereby improving the quality factor of the resonator. In this embodiment, the bulk acoustic wave resonator is a thin-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 effective resonance region and an ineffective region. The area on the cavity 200 where the top electrode 180 and the bottom electrode 140 overlap is the effective resonance area, and the remaining area is the ineffective area. Among them, the shape of the effective resonance region can be any shape, for example, 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 the air, so that the leaked sound waves are totally reflected at the interface between the bottom electrode 140 and the air, thereby increasing the electromechanical coupling coefficient and Q value of the bulk acoustic wave resonator, and correspondingly increasing the bulk acoustic wave The performance of the resonator. As an example, the longitudinal cross-sectional shape of the cavity 200 is an inverted trapezoid, that is, the cavity 200 includes four side walls, and the top dimension of the cavity 200 is larger than the bottom dimension. The size of the top of the cavity 200 is larger than the size of the bottom, and it is easy for the leaked sound wave to achieve total reflection at the junction of the bottom electrode 140 and the air.

The number of the cavity 200 is at least one. In this embodiment, the substrate 100 includes a plurality of resonator unit regions (not labeled), and each resonator unit region is formed with a cavity 200. Therefore, the number of cavities 200 is more than A bulk acoustic wave resonator is formed on 100, thereby realizing mass production. Among them, for ease of illustration, only one resonator unit area is shown in the figure.

Part of the boundary of the bottom electrode 140 is located on the cavity 200 and partially extends to the etch stop layer 120 on 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 is formed with a cavity 200. Therefore, the number of bottom electrodes 140 is correspondingly multiple, and the multiple bottom electrodes 140 is arranged separately, and the bottom electrode 140 corresponds to the unit area of the resonator one-to-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. In this embodiment, the material of the bottom electrode 140 is 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 laminated structure, and the acoustic impedance is different. The acoustic wave will be reflected at the interface where the acoustic impedance does not match, thereby realizing the effect of reflecting the acoustic wave. To maintain the shock. Among them, the piezoelectric acoustic resonance laminate 550 in the ineffective region is prone to generate parasitic capacitance. By making a part of the boundary of the bottom electrode 140 above the cavity 200 to isolate the effective resonance region and the ineffective region, the parasitic capacitance pair is located in the effective resonance region. The effect of the piezoelectric acoustic resonance laminate 550.

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

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

In this embodiment, part of the boundary of the top electrode 180 is located on the cavity 200 and partly extends to the substrate 100 on the periphery of the cavity 200. Therefore, in the process of forming the release hole 190 penetrating the piezoelectric acoustic resonance stack 550, the release hole 190 may not penetrate the three layers of the top electrode 180, the piezoelectric layer 170 and the bottom electrode 160, which is beneficial to reduce the formation of the release hole 190. The difficulty of the process. In this embodiment, the top electrode 180 and the bottom electrode 170 in the ineffective area are staggered from each other, thereby reducing the parasitic capacitance generated by the piezoelectric acoustic resonance laminate 550 in the ineffective area.

The flat layer 500 and the bottom electrode 140 are located in the same layer, and the top surface of the flat layer 500 is flush with the top surface of the bottom electrode 140. During 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 will not cover the sidewall of the bottom electrode 140, and the piezoelectric layer 170 can be kept flat at the junction of the piezoelectric layer 170 and the bottom electrode 140.

In this embodiment, the flat layer 500 is made of an insulating material, which can avoid the existence of upper and lower conductive layers facing the periphery of the effective resonance region, thereby avoiding parasitic resonance effects, and thus can better improve the performance of the resonator. Specifically, the material of the flat layer 500 includes one or more of silicon oxide, silicon nitride, carbon, carbon-containing compounds, and germanium, wherein the carbon atom percentage content in the carbon-containing compound is greater than 50%. As an example, the material of the flat layer 500 is silicon nitride. Silicon nitride has a high dielectric constant and has a good insulating effect. In other embodiments, the material of the flat layer may also be silicon oxide.

There is a gap 155 between the flat layer 500 and the bottom electrode 140. The air medium in the gap 155 and the bottom electrode 140 are made of different materials, which can also form a mismatched acoustic impedance interface, thereby reflecting transverse waves, thereby increasing the Q value of the bulk acoustic wave resonator.

In this embodiment, the flat layer 500 includes: a first sub-flat layer 150 on the substrate 100 on the outer periphery of the cavity 200, the first sub-flat layer 150 and the bottom electrode 140 enclose a gap 155; and a second sub-flat layer 160, It is located in the area enclosed by the piezoelectric layer 170, the bottom electrode 140 layer, the first sub-flat layer 150 and the substrate 100. In other words, the area communicating with the release hole 190 does not have the second sub-flat layer 160. During the manufacturing process of the bulk acoustic wave resonator, the second sub-flat 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-flat layer is removed through the release hole 190 160. The process of forming the second sub-planar layer 160 includes a planarization process. Therefore, in this embodiment, the first sub-planar layer 150 is first formed to cover most of the area, which is beneficial to improve the planarization when the second sub-planar layer 160 is formed. In order to improve the flatness of the top surface of the second sub-flat layer 160, the flatness of the top surface of the flat layer 500 is correspondingly improved, thereby improving the flatness of the piezoelectric layer 170.

In this embodiment, the first sub-flat layer 150 is made of insulating material, which can avoid the presence of upper and lower conductive layers at the periphery of the effective resonance region, thereby avoiding parasitic resonance effects. Specifically, the material of the first sub-planar layer 150 includes one or more of silicon oxide, silicon nitride, carbon, carbon-containing compounds, 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-planar layer 150 is silicon nitride. In other embodiments, the material of the first flat layer may also be silicon oxide. In other embodiments, the material of the bottom electrode and the material of the first sub-flat layer can also be the same, so that the bottom electrode and the first sub-flat layer can be formed in the same step, thereby simplifying the process steps.

In this embodiment, the second sub-flat layer 160 is made of an insulating material, which can avoid the presence of upper and lower conductive layers facing the effective resonance region, thereby avoiding parasitic resonance effects. Specifically, the material of the second sub-planar layer 160 includes one or more of silicon oxide, silicon nitride, carbon, carbon-containing compounds, and germanium, wherein the carbon atom percentage content in the carbon-containing compound is greater than 50%. By selecting the above-mentioned materials, when the second sub-flat layer 160 is removed through the release hole 190, the influence on the bottom electrode 140 is small. In this embodiment, the material of the second sub-planar layer 160 is the same as that of the sacrificial layer 130 and the first sub-planar layer 150, so that the second sub-planar layer 160 and the sacrificial layer 130 can be removed in the same manufacturing process, thereby simplifying the process complexity. Moreover, damage to the first sub-flat layer 150 can be reduced. Correspondingly, the material of the second sub-flat layer 160 is amorphous carbon. In other embodiments, the materials of the second sub-planar layer and the sacrificial layer may also be different.

In this embodiment, the gap 155 extends along the boundary of the effective resonance region, so that the sidewall of the bottom electrode 140 can be in contact with the air medium. As an example, a part of the boundary between the flat layer 500 and the top electrode 140 encloses a closed annular gap 155, that is, the flat layer 500 surrounds the top electrode 140 and has a gap 155 between the flat layer 500 and the top electrode 140. In other embodiments, a part of the boundary between the flat layer and the top electrode forms a ring 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 with gaps.

The width of the gap 155 should not be too small or too large. If the width of the gap 155 is too small, it will be difficult to fill the gap 155 with the material of the second sub-flat layer 160, which will easily lead to low flatness of the top surface of the second sub-flat layer 160, and accordingly it is difficult to improve the flatness of the piezoelectric layer 170. Degree; if the width of the gap 155 is too large, when the second sub-flat layer 160 is formed, the effect of improving the recession problem is not good, which is not conducive to improving the flatness of the top surface of the second sub-flat layer 160, and it is difficult to improve the piezoelectric layer 170 flatness. For this reason, in this embodiment, the width of the gap 155 is 1 nanometer to 100 nanometers.

During the manufacturing process of the bulk acoustic wave resonator, the sacrificial layer in the cavity 200 is removed through the release hole 190. In this embodiment, the number of release holes 190 is multiple, thereby improving the efficiency of removing the sacrificial layer. In this embodiment, the release hole 190 penetrates the top electrode 180 or the bottom electrode 170, that is, the release hole 190 penetrates the piezoelectric acoustic resonance laminate 550 located in the invalid region, but does not penetrate the piezoelectric acoustic resonance laminate in the effective resonance region. 550. Therefore, in the process of forming the release hole 190, the piezoelectric acoustic resonance laminate 550 in the effective resonance area is not etched, which is beneficial to reduce the influence on the piezoelectric acoustic resonance laminate 550 located in the effective resonance area. It is beneficial to improve the reliability of the bulk acoustic wave resonator.

Specifically, according to the formation position of the release hole 190 and the laminated structure of the piezoelectric acoustic resonance laminate 550 corresponding to the position, the release hole 190 may penetrate the top electrode 180 and the piezoelectric layer 170 and communicate with the cavity 200; or , The release hole 190 penetrates the piezoelectric layer 170 and the flat layer 500 and communicates with the cavity 200; or, the release hole 190 penetrates the top electrode 180, the piezoelectric layer 170, and the flat layer 500 and communicates with the cavity 200; or, release The hole 190 penetrates the piezoelectric layer 170 and communicates with the cavity 200.

In this embodiment, the bulk acoustic wave resonator further includes an etch stop layer 120, which is located between the flat layer 500 and the substrate 100 and extends to cover the sidewall and bottom of the cavity 200. The etch stop layer 120 is used to achieve electrical isolation between the substrate 100 and the bottom electrode 140; moreover, the process of forming the bottom electrode 140 includes sequential deposition and etching processes. The etch stop layer 120 is used to form the bottom electrode 140. During the process, the etching stop position is defined, thereby reducing damage to the substrate 100. Correspondingly, the etching stop layer 120 is also used to protect the substrate 100. In addition, during 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 to define the stop position of the planarization process, thereby It is beneficial to improve the surface flatness of the sacrificial layer.

The material of the etch stop layer 120 is an insulating material to realize electrical isolation between the substrate 100 and the bottom electrode. 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 should not be too small or too large. If the thickness is too small, the above-mentioned performance of the etch stop layer 120 is difficult to be guaranteed; if the thickness is too large, the flatness of the etch stop layer 120 is difficult to ensure, thereby affecting the quality of the subsequent film formation. For this reason, in this embodiment, the thickness of the etch stop layer 120 is 50 nanometers to 1000 nanometers.

The resonator described in this embodiment may be formed by the manufacturing method described in the foregoing embodiments, or may be formed by other manufacturing methods. For the specific description of the resonator in this embodiment, reference may be made to the corresponding description in the foregoing embodiment, and this embodiment will not be repeated here.

Correspondingly, the embodiment of the present invention also provides another bulk acoustic wave resonator. Continuing to refer to FIG. 15, there is shown a schematic structural diagram of an embodiment of a bulk acoustic wave resonator of the present invention. Wherein, FIG. 15a is a cross-sectional view along the first direction, and FIG. 15b is a cross-sectional view along the second direction, and the first direction and the second direction are perpendicular.

The similarities between the embodiment of the present invention and the foregoing embodiment will not be repeated here. The difference between the embodiment of the present invention and the foregoing embodiment is that there is no gap between the flat layer 350 and the bottom electrode 340.

Specifically, the bulk acoustic wave resonator includes: a substrate 300 with a cavity 400 in the substrate 300; a piezoelectric acoustic resonance stack (not labeled), located on the substrate 100, the piezoelectric acoustic resonance stack includes a part of the boundary in the cavity A bottom electrode 340 on the cavity 400 that partially extends outside the cavity 400, a piezoelectric layer 370 on the bottom electrode 340 and a piezoelectric layer 370 extending flat on the end of the bottom electrode 340, and a top electrode 380 on the upper surface of the piezoelectric layer 370 The flat layer 350 is located in the same layer as the bottom electrode 340, the top surface of the flat layer 350 is flat with the top surface of the bottom electrode 340, and the flat layer 350 is in contact with the bottom electrode 340 and covers the exposed substrate 100 of the bottom electrode 340; a release hole penetrates The piezoelectric acoustic resonant layer is laminated and communicated with the cavity 400.

In this embodiment, the flat layer 350 is an integral structure, that is, the same step is used to form the flat layer during the manufacturing process of the bulk acoustic wave resonator. Correspondingly, the flat layer 350 of this embodiment is located on the bottom surface of the piezoelectric layer exposed by the bottom electrode. The material of the flat layer 350 is an insulating material, so as to avoid the occurrence of parasitic resonance effects at the periphery of the effective resonance region, and thus can better improve the performance of the resonator. Specifically, the material of the planarization layer 350 includes one or more of silicon oxide, silicon nitride, carbon, carbon-containing compounds, and germanium.

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

Correspondingly, an embodiment of the present invention also provides a filter including the bulk acoustic wave resonator provided in the foregoing embodiment. The bulk acoustic wave resonator of the foregoing embodiment has a higher quality factor, which correspondingly improves the performance of the filter.

Correspondingly, an embodiment of the present invention also provides an electronic device, including the filter provided in the foregoing embodiment. The filter can be assembled into various electronic devices. From the foregoing analysis, it can be seen that the filter has a higher performance, which correspondingly can obtain a higher performance electronic device. Among them, electronic equipment can be personal computers, smart phones and other mobile terminals, media players, navigation equipment, electronic game equipment, game controllers, tablet computers, wearable devices, anti-access electronic systems, POS terminals, medical equipment, flying Simulator etc.

Although the present invention is disclosed as above, the present invention is not limited to this. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

A method for manufacturing a bulk acoustic wave resonator, which is characterized in that it comprises:

Providing a substrate with a groove formed in the substrate;

Filling the groove to form a sacrificial layer in the groove;

Forming a bottom electrode on the sacrificial layer, a part of the boundary of the bottom electrode is located above the groove and partly extends to the substrate on the periphery of the groove;

Forming a flat layer on the substrate exposed by the bottom electrode and in contact with the sidewall of the bottom electrode, and the top surface of the flat layer is flush with the top surface of the bottom electrode;

Forming a piezoelectric layer covering the bottom electrode and the flat layer;

Forming a top electrode on the piezoelectric layer, and the piezoelectric acoustic resonance stack includes a bottom electrode, a piezoelectric layer and a top electrode;

Forming a release hole penetrating the piezoelectric acoustic resonance laminate;

The sacrificial layer is removed through the release hole to form a cavity.
The manufacturing method of claim 1, wherein the method for forming the flat layer comprises: forming a first sub-flat layer on the substrate on the outer periphery of the groove, the first sub-flat layer and The bottom electrode encloses a gap, and the top surface of the first sub-flat layer is flush with the top surface of the bottom electrode;

A second sub-flat layer is formed in the gap, and the top surface of the second sub-flat layer is flush with the top surface of the bottom electrode.
The manufacturing method according to claim 2, wherein the manufacturing method further comprises: removing the second sub-flat layer through the release hole.
The manufacturing method according to claim 3, wherein the material of the second sub-flat layer and the sacrificial layer are the same.
The manufacturing method of claim 2, wherein the material of the bottom electrode is the same as the material of the first sub-flat layer, and in the same step, the bottom electrode and the first sub-flat layer are formed ；

Alternatively, the material of the first sub-flat layer is an insulating material.
The manufacturing method according to claim 1, wherein part of the boundary of the top electrode is located on the groove, and partly extends to the substrate on the periphery of the groove.
8. The manufacturing method according to claim 1, wherein after forming the flat layer, a bottom electrode is formed in the exposed area of the flat layer;

Alternatively, after forming the bottom electrode of the substrate located on the sacrificial layer and extending to cover a part of the outer periphery of the groove, a flat layer is formed in the exposed area of the bottom electrode.
The manufacturing method according to claim 1, wherein after forming the bottom electrode, the flat layer is formed by a metal lift-off process, or, after the bottom electrode is formed, the deposition and flattening of corresponding materials are performed, The flat layer is formed.
8. The manufacturing method of claim 1, wherein the top electrode and the bottom electrode in the ineffective area are staggered from each other.
The manufacturing method according to claim 2, wherein the gap extends along the boundary of the effective resonance region.
The manufacturing method of claim 10, wherein a part of the boundary between the first sub-flat layer and the top electrode forms a closed annular gap; or, the first sub-flat layer and the top electrode Part of the boundary of is enclosed in a ring with gaps.
The manufacturing method according to claim 1, wherein after forming the groove in the substrate, before forming the sacrificial layer in the groove, the manufacturing method further comprises: forming the substrate on the substrate An etch stop layer is formed, and the etch stop layer also conformally covers the bottom and sidewalls of the groove.
The manufacturing method of claim 1, wherein the material of the sacrificial layer includes one or more of silicon oxide, carbon, carbon-containing compound, and germanium, wherein the carbon atoms in the carbon-containing compound The percentage content is greater than 50%.
The manufacturing method according to claim 1, wherein the material of the flat layer includes one or more of silicon oxide, silicon nitride, carbon, carbon-containing compound, and germanium, wherein the carbon-containing compound The carbon atom percentage content in is greater than 50%.
The manufacturing method according to claim 2, wherein the width of the gap is 1 nanometer to 100 nanometers.
A bulk acoustic wave resonator, characterized in that it comprises:

A substrate having a cavity therein;

A piezoelectric acoustic resonant laminate is located on the substrate, and the piezoelectric acoustic resonant laminate includes a bottom electrode partly bordered on the cavity, partly extending outside the cavity, and located on the bottom electrode And having a piezoelectric layer extending flatly at the end of the bottom electrode, and a top electrode located on the upper surface of the piezoelectric layer;

A flat layer located 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 there is a gap between the bottom electrode;

The release hole penetrates the piezoelectric acoustic resonance stack and communicates with the cavity.
The bulk acoustic wave resonator according to claim 16, wherein part of the boundary of the top electrode is located on the cavity, and partly extends to the substrate on the periphery of the cavity.
The bulk acoustic wave resonator according to claim 16, wherein the top electrode and the bottom electrode of the ineffective area are staggered from each other.
The bulk acoustic wave resonator according to claim 16, wherein the gap extends along the boundary of the effective resonance region.
The bulk acoustic wave resonator according to claim 19, wherein a part of the boundary between the flat layer and the top electrode forms a closed annular gap; or, a part of the boundary between the flat layer and the top electrode surrounds Into a ring with gaps.
The bulk acoustic wave resonator according to claim 16, wherein the area on the cavity where the top electrode and the bottom electrode overlap is an effective resonance region, and the shape of the effective resonance region is an irregular polygon.
The bulk acoustic wave resonator according to claim 16, wherein the material of the flat layer includes one or more of silicon oxide, silicon nitride, carbon, carbon-containing compounds, and germanium, wherein the material containing The carbon atom percentage content in the carbon compound is greater than 50%.
The bulk acoustic wave resonator of claim 16, wherein the width of the gap is 1 nanometer to 100 nanometers.
The bulk acoustic wave resonator of claim 16, wherein the resonator further comprises: an etch stop layer, located between the flat layer and the substrate, and extending to cover the side of the cavity Wall and bottom.
The bulk acoustic wave resonator of claim 24, wherein the thickness of the etch stop layer is 50 nanometers to 1000 nanometers.
A bulk acoustic wave resonator, characterized in that it comprises:

A substrate having a cavity therein;

A piezoelectric acoustic resonant laminate is located on the substrate, and the piezoelectric acoustic resonant laminate includes a bottom electrode partly bordered on the cavity, partly extending outside the cavity, and located on the bottom electrode And having a piezoelectric layer extending flatly at the end of the bottom electrode, and a top electrode located on the upper surface of the piezoelectric layer;

The flat layer is located in the same layer as the bottom electrode, the top surface of the flat layer is flat 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 ；

The release hole penetrates the piezoelectric acoustic resonance stack and communicates with the cavity.
A filter characterized by comprising the bulk acoustic wave resonator according to any one of claims 16 to 25.
A filter characterized by comprising the bulk acoustic wave resonator according to claim 26.
An electronic device, characterized by comprising the filter according to claim 27.
An electronic device, characterized by comprising the filter according to claim 28.