JP7138988B2 - Bulk acoustic wave resonator, manufacturing method thereof, filter, radio frequency communication system - Google Patents

Description

TECHNICAL FIELD The present invention relates to the technical field of radio frequency communication, and more particularly to a bulk acoustic wave resonator and its manufacturing method and filter, radio frequency communication system.

Radio frequency (RF) communications, such as those used in cell phones, require the use of radio frequency filters, each of which transmits desired frequencies and limits all other frequencies. can be done. With the development of mobile communication technology, the amount of mobile data transferred is also increasing rapidly. Therefore, on the premise that frequency resources are limited and the need to use as few mobile communication devices as possible, it is difficult to improve the transmission power of wireless power transmission devices such as radio base stations, micro base stations or repeaters. , becomes a matter of consideration and also means that the filter power requirements in the front-end circuits of mobile communication devices are also high.

Conventionally, high-power filters in devices such as wireless base stations are mainly cavity filters, whose power reaches 100 watts, but the size of such filters is too large. Some devices use dielectric filters, the average power of which can reach 5 Watts or more, and the size of this filter is also large. Due to their large size, these two filters cannot be integrated into a radio frequency front-end chip.

As MEMS technology matures, filters composed of bulk acoustic wave (BAW) resonators can successfully overcome the existing deficiencies of the above two filters. Bulk acoustic wave resonators have volume advantages incomparable with ceramic dielectric filters, operating frequency and power capacity advantages incomparable with surface acoustic wave (SAW) resonators, and are a trend of current wireless communication systems. It has become.

The main body of the bulk acoustic wave resonator has a “sandwich” structure consisting of a bottom electrode, a piezoelectric thin film, and a top electrode. A standing wave is formed in the form of an acoustic wave in a filter composed of acoustic wave resonators. Since the speed of acoustic waves is five orders of magnitude smaller than that of electromagnetic waves, the size of filters composed of bulk acoustic wave resonators is smaller than that of conventional dielectric filters.

The working principle of one type of cavity bulk acoustic wave resonator is to use acoustic waves to reflect at the interface between the bottom electrode or support layer and the air, confining the acoustic waves to the piezoelectric layer to achieve resonance. It has advantages such as high Q factor, low insertion loss, and integrability, and is widely adopted.

However, conventionally fabricated cavity-type bulk acoustic wave resonators cannot further improve their quality factor (Q) and meet the demands of high-performance radio frequency systems.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bulk acoustic wave resonator, a method for manufacturing the same, a filter, and a radio frequency communication system that can improve the quality factor and the performance of the device.

In order to achieve the above object, according to the present invention,
a substrate;
A bottom electrode layer provided on the substrate, wherein a cavity is formed between the bottom electrode layer and the substrate, and a portion of the bottom electrode layer located above the cavity extends flat. a bottom electrode layer;
a piezoelectric resonance layer formed on the bottom electrode layer in an upper portion of the cavity;
a top electrode layer formed on the piezoelectric resonance layer, the top electrode layer being located in the region of the cavity on the outer circumference of the piezoelectric resonance layer and recessed in a direction close to the bottom surface of the cavity; and a top electrode layer having a peripherally extending top electrode recess surrounding the piezoelectric resonant layer.

The invention further provides a filter comprising at least one bulk acoustic wave resonator according to the invention.

The invention further provides a radio frequency communication system comprising at least one filter according to the invention.

Also according to the present invention, providing a substrate and forming a first sacrificial layer having a flat top surface on a portion of said substrate;
forming a bottom electrode layer on a portion of the first sacrificial layer, the portion located on the top surface of the first sacrificial layer extending flatly;
forming a piezoelectric resonance layer on the bottom electrode layer exposing a portion of the first sacrificial layer and a portion of the bottom electrode layer;
forming a second sacrificial layer having a first groove in an exposed area around the piezoelectric resonance layer;
A top electrode layer is formed on the piezoelectric resonance layer and a portion of the second sacrificial layer around the piezoelectric resonance layer, and a portion of the top electrode layer covering the first groove is used as a top electrode recess. forming;
removing the second sacrificial layer and the first sacrificial layer and forming a cavity at the location of the second sacrificial layer and the first sacrificial layer, wherein the top electrode recess is the piezoelectric located in the region of the cavity at the perimeter of a resonant layer and extending in a circumferential direction surrounding the piezoelectric resonant layer.

Compared with the prior art, the technical solution of the present invention has the following beneficial effects.
1. When electrical energy is applied to the bottom electrode and the top electrode, the piezoelectric phenomenon induced in the piezoelectric resonance layer produces a desired longitudinal wave propagating in the thickness direction and an undesirable transverse wave propagating along the plane of the piezoelectric resonance layer. Then, the transverse wave is blocked by the recessed portion of the top electrode on the cavity floating on the outer circumference of the piezoelectric resonance layer, reflected by the area corresponding to the piezoelectric resonance layer, and propagated to the film layer on the outer circumference of the cavity. This can improve the acoustic loss, improve the quality factor of the resonator, and ultimately improve the performance of the device.

2. The periphery of the piezoelectric resonance layer and the periphery of the cavity are separated from each other, that is, the piezoelectric resonance layer does not extend continuously above the substrate at the periphery of the cavity, and the effective operation of the bulk acoustic wave resonator The area can be completely confined to the cavity area, with both the bottom and top electrode bridges extending to only some sides of the cavity (i.e., the bottom and top electrode layers ), which reduces the influence of the membrane layer around the cavity on longitudinal vibrations induced in the piezoelectric resonant layer, improving performance.

3. Even if the top electrode recess and the bottom electrode layer have overlapping portions, there is a gap structure between the overlapping portions, which can greatly reduce the parasitic parameters, and the top electrode layer and the bottom electrode layer Problems such as electrical contact in the cavity region of the bottom electrode layer can be avoided and device reliability can be improved.

4. The overlapping portions of the bottom electrode bridge portion and the top electrode bridge portion with the cavity are all floating, and the bottom electrode bridge portion and the top electrode bridge portion are mutually displaced from the region of the cavity (that is, both , do not overlap in the cavity region), which can greatly reduce the parasitic parameters, avoid problems such as leakage and short circuits caused by contact between the bottom electrode bridge and the top electrode bridge, and make the device reliability can be improved.

5. The bottom electrode bridge completely covers the cavity above the portion of the cavity in which it is located, thereby using a large area bottom electrode bridge to strongly attach to the membrane layer above it. provide good mechanical support, thereby avoiding the problem of device failure due to cavity collapse.

6. The top electrode recess surrounds the entire periphery of the top electrode resonator, blocking transverse waves from the periphery of the piezoelectric resonance layer in all directions, and obtaining a better quality factor.

7. The bottom electrode resonance part and the bottom electrode bridge part are formed of the same film layer and have a uniform film thickness, and the top electrode recess part, the top electrode resonance part and the top electrode bridge part are formed of the same film layer, The film thickness is uniform, which simplifies the process and reduces the cost, and the thickness of the top electrode recess is approximately the same as the rest of the top electrode layer, so that the top electrode recess is Device reliability can be improved without disconnection situations.

8. The part of the bottom electrode layer located in the cavity area is flat, which can contribute to improving the thickness uniformity of the thin film in the effective area, and the etching process when forming the piezoelectric resonance layer. and avoids the problem of not completely etching the piezoelectric material because the top surface of the bottom electrode layer is not flat, thereby reducing the parasitic parameters.

1 is a top structural schematic diagram of a bulk acoustic wave resonator according to an embodiment of the present invention; FIG. FIG. 2 is a schematic cross-sectional view taken along lines XX' and YY' in FIG. 1; FIG. 2 is a schematic cross-sectional view taken along lines XX' and YY' in FIG. 1; FIG. 4 is a top structural schematic diagram of a bulk acoustic wave resonator according to another embodiment of the present invention; FIG. 4 is a top structural schematic diagram of a bulk acoustic wave resonator according to another embodiment of the present invention; FIG. 4 is a top structural schematic diagram of a bulk acoustic wave resonator according to another embodiment of the present invention; FIG. 5 is a schematic cross-sectional view of a bulk acoustic wave resonator according to another embodiment of the present invention; 1 is a flow chart of a method for manufacturing a bulk acoustic wave resonator according to one embodiment of the present invention; It is a cross-sectional schematic diagram along XX' in FIG. 1A in the manufacturing method of the bulk acoustic wave resonator of one Example of this invention. It is a cross-sectional schematic diagram along XX' in FIG. 1A in the manufacturing method of the bulk acoustic wave resonator of one Example of this invention. It is a cross-sectional schematic diagram along XX' in FIG. 1A in the manufacturing method of the bulk acoustic wave resonator of one Example of this invention. It is a cross-sectional schematic diagram along XX' in FIG. 1A in the manufacturing method of the bulk acoustic wave resonator of one Example of this invention. It is a cross-sectional schematic diagram along XX' in FIG. 1A in the manufacturing method of the bulk acoustic wave resonator of one Example of this invention. It is a cross-sectional schematic diagram along XX' in FIG. 1A in the manufacturing method of the bulk acoustic wave resonator of one Example of this invention. 1B is a schematic cross-sectional view along XX' in FIG. 1A in the method for manufacturing a bulk acoustic wave resonator according to another embodiment of the present invention; FIG.

The technical solutions of the present invention are further described in detail below with reference to the drawings and specific embodiments. Based on the following description, the effects and features of the present invention will become clearer. It should be noted that the drawings are all in a greatly simplified form, imprecise proportions, and are merely for the purpose of providing an easy, clear and supplemental explanation of the embodiments of the present invention. Similarly, to the extent that the methods described herein include a series of steps, the order of these steps presented herein is not the only order in which these steps may be performed, and some said steps may include: Some other steps may be omitted and/or not described herein may be added to the method. Further, what is meant herein by "relatively offset" is that they do not overlap in the cavity area, ie their projections at the bottom of the cavity do not overlap.

1A to 1C, FIG. 1A is a top structural schematic diagram of a bulk acoustic wave resonator of one embodiment of the present invention, and FIG. 1B is a cross-sectional structural schematic diagram along XX' in FIG. FIG. 1C is a schematic cross-sectional view along line YY' in FIG. and layer 108 .

The substrate includes a base 100 and an etching protection layer 101 coated on the base 100 . The base 100 may be any suitable substrate known to those skilled in the art, such as silicon (Si), germanium (Ge), silicon germanium (SiGe), silicon carbide (SiC), silicon germanium carbide (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP), or other III/V compound semiconductors, multilayer structures composed of these semiconductors, etc. May be one or Silicon on Insulator (SOI), Stacked Silicon on Insulator (SSOI), Stacked Silicon Germanium on Insulator (S-SiGeOI), Stacked Silicon Germanium on Insulator (SiGeOI) and Germanium on Insulator (GeOI), or Double Side Polished Wafers (DSP), ceramic-based such as aluminum oxide, Sekiei , or may be a glass base or the like. The material of the etching protection layer 101 may be any suitable dielectric material, including but not limited to at least one of silicon oxide, silicon nitride, silicon nitrogen oxide, silicon carbonitride, and the like. can't The etching protection layer, on the other hand, improves the structural stability of the finally manufactured bulk acoustic wave resonator, strengthens the isolation between the bulk acoustic wave resonator and the base 100, and reduces the resistivity requirements for the base 100. can be reduced while protecting other areas of the substrate from being etched during fabrication of the bulk acoustic wave resonator, thereby improving device performance and reliability.

A cavity 102 is formed between the bottom electrode layer 104 and the substrate. 1A-1C, in this embodiment, the cavity 102 may be formed by sequentially etching the thickness of the etching protection layer 101 and part of the base 100 by an etching process, and the bottom The whole becomes a second groove structure recessed in the substrate. However, the technique of the present invention is not limited to this, and referring to FIG. 2D, in another embodiment of the present invention, the cavity 102 is followed by a sacrificial layer protruding from the surface of the etching protection layer 101 . Through the process of removing using a removing method, it may be formed above the top surface of the etching protection layer 101 , resulting in a cavity structure that protrudes over the surface of said etching protection layer 101 as a whole. Also, in this embodiment, the shape of the bottom surface of the cavity 102 may be rectangular, but in other embodiments of the present invention, the shape of the bottom surface of the cavity 102 may also be circular, elliptical, or other than rectangular. polygon (eg, pentagon, hexagon).

The piezoelectric resonant layer 1051, which may be called a piezoelectric resonant part, is located in the upper region of the cavity 102 (i.e., located within the region of the cavity 102) and corresponds to the effective working area of the bulk acoustic wave resonator. and is provided between the bottom electrode layer 104 and the top electrode layer 108 . The bottom electrode layer 104 includes a bottom electrode bridge portion 1040 and a bottom electrode resonance portion 1041 which are connected in sequence, and the portion of the bottom electrode layer 104 located above the cavity 102 extends flatly, that is, The top surface of the portion of the bottom electrode bridge portion 1040 located above the cavity and the top surface of the bottom electrode resonance portion 1041 are flush with each other, and the bottom surface of the portion of the bottom electrode bridge portion 1040 located above the cavity and the top surface of the bottom electrode resonance portion 1041 are flush with each other. The bottom surface of the bottom electrode resonance portion 1041 is flush with the bottom surface. The top electrode layer 108 includes a top electrode bridge portion 1080, a top electrode recess portion 1081, and a top electrode resonance portion 1082, which are connected in order. , the bottom electrode resonator 1041, the piezoelectric resonator layer 1051, and the top electrode resonator 1082, which form an effective operating area 102A of the bulk acoustic wave resonator. A portion other than 102A is an ineffective region 102B, and the piezoelectric resonance layer 1051 is located in the effective operating region 102A and is separated from the film layers surrounding the cavity 102 to make the effective operating region of the bulk acoustic wave resonator into the cavity 102A. to reduce the influence of the film layers around the cavity on the longitudinal vibrations induced in the piezoelectric resonant layer, reduce the parasitic parameters induced in the dead region 102B, and improve the performance of the device. can be improved. The bottom electrode resonance part 1041, the piezoelectric resonance layer 1051, and the top electrode resonance part 1082 are all flat structures with flat upper and lower surfaces, and the 1081 is positioned above the cavity 102B on the outer periphery of the effective operation area 102A. and is electrically connected to the top electrode resonant portion 1082 and is recessed in a direction approaching the bottom surface of the cavity 102 , and the entire top electrode recessed portion 1081 is downward with respect to the top surface of the top electrode resonant portion 1082 . It is recessed and located in the cavity region (ie 102B) at the outer circumference of the piezoelectric resonance layer 1051 . The top electrode recess 1081 may have a solid structure or a hollow structure, preferably a hollow structure. It avoids the collapsing deformation of the top electrode resonance part 1082 and the piezoelectric resonance layer 1051 and the bottom electrode resonance part 1041 caused by the actual top electrode recess 1081, and further improves the resonance coefficient. Both the bottom electrode resonance portion 1041 and the top electrode resonance portion 1082 are polygonal (the top surface and the bottom surface are both polygonal), and the shapes of the bottom electrode resonance portion 1041 and the top electrode resonance portion 1082 may be similar (shown in FIGS. 2A-2C and 2D) or completely identical (shown in FIGS. 1A and 2B). The piezoelectric resonance layer 1051 has a polygonal structure similar to the shapes of the bottom electrode resonance part 1041 and the top electrode resonance part 1082 .

1A to 1C, in this embodiment, the bottom electrode layer 104, the piezoelectric resonance layer 1051 and the top electrode layer 108 constitute a "watch"-like film layer structure, and the bottom electrode bridge portion 1040 is the bottom electrode resonance layer. Aligned with one corner of portion 1041, with top electrode bridge portion 1080 aligned with one corner of top electrode resonator portion 1082, bottom electrode bridge portion 1040 and top electrode bridge portion 1080 form two bands of a "watch". and the top electrode recessed portion 1081 is provided along the side of the top electrode resonant portion 1082 and provided only in a region where the top electrode bridge portion 1080 and the top electrode resonant portion 1082 are aligned. The top electrode recess 1081 corresponds to the connection structure between the dial of a "watch" and one band, and includes the bottom electrode resonance part 1041, the piezoelectric resonance layer 1051, and the top electrode resonance part in the effective area 102A. The laminated structure of 1082 corresponds to the dial of a wrist watch, in which the band part is connected to the film layer on the substrate around the cavity, and the remaining parts are all connected to the cavity around the cavity through the cavity. Separated from the membrane layer on the substrate. That is, in this embodiment, the top electrode recessed portion 1081 extends around the piezoelectric resonance layer 1051 in the peripheral direction, and the top electrode recessed portion 1081 extends along the peripheral direction of the piezoelectric resonance layer 1051. , surrounded only by some sides of the piezoelectric resonance layer 1051, referring to the plane where the piezoelectric resonance layer 1051 is located, the top electrode recess 1081 and the bottom electrode bridge 1040 are formed on both sides of the piezoelectric resonance layer 1051, respectively. located and facing each other, thereby achieving a certain transverse wave blocking effect and contributing to a reduction in the area of the dead region 102B not covered by the top electrode bridge portion 1080 and the bottom electrode bridge portion 1040, further improving the device. It contributes to size reduction and contributes to a reduction in the area of the top and bottom electrode bridges 1080 and 1040, further reducing parasitic parameters and improving the electrical performance of the device. The bottom electrode bridge part 1040 is electrically connected to one side of the bottom electrode resonance part 1041 and is a cavity (ie, 102B) floating above the bottom electrode resonance part 1041 to the outside of the bottom electrode resonance part 1041 . , and extends to above a portion of the etching protection layer 101 on the outer periphery of the cavity 102 , and the top electrode bridge portion 1080 extends to the top electrode resonance portion 1082 of the top electrode recess portion 1081 . is electrically connected to the opposite side of the cavity 102, and after passing above the cavity (that is, 102B) floating outside the top electrode recess 1081 from above the top electrode recess 1081, Extending above a portion of the etching protection layer 101 at the perimeter, the bottom electrode bridge portion 1040 and the top electrode bridge portion 1080 extend above the substrate outside two opposite sides of the cavity 102. At this time, the bottom electrode bridge portion 1040 and the top electrode bridge portion 1080 are mutually offset (i.e., do not overlap) in the cavity 102 region, thereby reducing parasitic parameters and reducing the bottom electrode Problems such as leaks and short circuits due to contact between the bridge portion and the top electrode bridge portion can be avoided, and the performance of the device can be improved. The bottom electrode bridge portion 1040 is used to transfer the corresponding signal to the bottom electrode resonance portion 1041 by connecting the corresponding signal line, and the top electrode bridge portion 1080 connects the corresponding signal line. is used to transfer a corresponding signal to the top electrode resonator 1082 via the top electrode recess 1081, thereby allowing the bulk acoustic wave resonator to operate normally, specifically, the bottom By applying a time-varying voltage to the bottom electrode resonance portion 1041 and the top electrode resonance portion 1082 via the electrode bridge portion 1040 and the top electrode bridge portion 1080, respectively, a longitudinal extension mode or a “piston” mode is excited. , the piezoelectric resonant layer 1051 converts energy in the form of electrical energy into longitudinal waves, generating parasitic transverse waves in the process, and the top electrode recesses 1081 allow these transverse waves to propagate to the membrane layers at the periphery of the cavity. It can be blocked and confined to the region of the cavity 102, thereby avoiding energy losses due to shear waves and improving the quality factor.

Preferably, the line width of the top electrode recess 1081 is the minimum line width allowed for the corresponding process, and the horizontal distance between the top electrode recess 1081 and the piezoelectric resonance layer 1051 is the same as the corresponding process. This is the minimum distance allowed for the top electrode recess 1081, which allows the top electrode recess 1081 to achieve a desired transverse wave blocking effect and contributes to the reduction of the device area.

Also, the side wall of the top electrode recess 1081 is a side wall inclined with respect to the top surface of the piezoelectric resonance layer, and as shown in FIG. has a trapezoidal or trapezoidal-like shape, and the angles α1 and α2 between the two sidewalls of the top electrode recess 1081 and the top surface of the piezoelectric resonance layer 1051 are both 45 degrees or less. This avoids that the side wall of the top electrode recess 1081 is too vertical, causing the top electrode recess 1081 to be cut and further affecting the effect of transferring the signal to the top electrode resonance part 1082, Also, the thickness uniformity of the entire top electrode layer 108 can be further improved.

In one preferred embodiment of the present invention, the bottom electrode resonator portion 1041 and the bottom electrode bridge portion 1040 are formed in the same film layer manufacturing process (that is, the same film layer manufacturing process), and the top electrode resonator portion 1082 and the top electrode bridge portion 1082 are formed in the same film layer manufacturing process. The electrode recess portion 1081 and the top electrode bridge portion 1080 are formed in the same film layer manufacturing process (that is, the same film layer manufacturing process), that is, the bottom electrode resonance portion 1041 and the bottom electrode bridge portion 1040 are integrally manufactured. The top electrode resonator portion 1082, the top electrode recess portion 1081 and the top electrode bridge portion 1080 are integrally fabricated film layers, which simplifies the process, reduces the cost, and reduces the cost of the bottom electrode. The film layer materials for fabricating the resonator portion 1041 and the bottom electrode bridge portion 1040, and the film layer materials for fabricating the top electrode resonator portion 1082, the top electrode recess portion 1081, and the top electrode bridge portion 1080 are Any suitable conductive or semiconductor material known in the art may be used, and the conductive material may be a metallic material having electrical conductivity, such as aluminum (Al), copper (Cu) , platinum (Pt), gold (Au), molybdenum (Mo), tungsten (W), iridium (Ir), osmium (Os), rhenium (Re), palladium (Pd), rhodium (Rh) and ruthenium (Ru) and the semiconductor material is, for example, Si, Ge, SiGe, SiC, SiGeC, or the like. In other embodiments of the present invention, the bottom electrode resonator portion 1041 and the bottom electrode bridge portion 1040 may be formed by different film layer manufacturing processes, subject to process cost and process technology permitting, and the top electrode resonator portion 1082, the top electrode recess 1081 and the top electrode bridge 1080 may be formed by different film layer fabrication processes.

2A-2C, the top electrode recess 1081 extends to more continuous sides of the top electrode resonator 1082 to further improve the shear wave blocking effect. For example, referring to FIG. 2A, the piezoelectric resonance layer 1051, the top electrode resonance part 1082 and the bottom electrode resonance part 1041 are all pentagonal planar structures, the area of the piezoelectric resonance layer 1051 is the smallest, and the top electrode resonance part 1082 is larger than that, and the area of the bottom electrode resonant portion 1041 is the largest, and the top electrode recessed portion 1081 is provided along a plurality of sides of the top electrode resonant portion 1082 and is connected to these sides so that the bottom electrode The projection of the connection portion between the electrode resonance portion 1041 and the bottom electrode bridge portion 1040 on the bottom surface of the cavity 102 is exposed from the projection of the top electrode recess portion 1081 on the bottom surface of the cavity 102 . and the bottom electrode bridge portion 1040 are prevented from overlapping each other, and the parasitic parameter can be further reduced. For example, referring to FIG. 2B, the piezoelectric resonance layer 1051, the top electrode resonance section 1082, and the bottom electrode resonance section 1041 all have a pentagonal planar structure, the area of the piezoelectric resonance layer 1051 is the smallest, and the top electrode resonance section 1082 and the bottom electrode resonance part 1041 have the same or substantially the same area, shape, etc. The bottom electrode resonance portion 1041 and the projection on the bottom surface of the cavity 102 are superimposed, whereby the transverse wave generated by the piezoelectric resonance layer 1051 can be omnidirectionally blocked by the top electrode recess portion 1081 presenting a closed annular shape. .

2A-2C, in these embodiments of the present invention, the bottom electrode bridge portion 1040 is electrically connected to at least one side or at least one corner of the bottom electrode resonant portion 1041, After passing above the cavity (that is, 102B) floating outside the bottom electrode resonance part 1041 from the corresponding side of the bottom electrode resonance part 1041, part of the etching protection layer 101 on the outer periphery of the cavity 102 is etched. The top electrode bridge portion 1080 is electrically connected to at least one side or at least one corner of the top electrode recess portion 1081 facing away from the top electrode resonance portion 1082 . After passing above the cavity (that is, 102B) floating outside the top electrode recess 1081 from the top electrode recess 1081, it extends to above a part of the etching protection layer 101 on the outer periphery of the cavity 102. , and the projections of the top electrode bridge portion 1080 and the bottom electrode bridge portion 1040 on the bottom surface of the cavity 102 may just be connected or separated from each other, thereby allowing the top electrode The bridge portion 1080 and the bottom electrode bridge portion 1040 are offset from each other in the region of the cavity 102 without overlapping. For example, as shown in FIGS. 1A and 2A-2B, the bottom electrode bridge portion 1040 extends above a portion of the substrate at the perimeter of only one side of the cavity 102 to provide the top electrode bridge. A portion 1080 extends above a portion of the substrate at the perimeter of only one side of the cavity 102 , and at the bottom surface of the cavity 102 between the top electrode bridge portion 1080 and the bottom electrode bridge portion 1040 . are separated from each other, thereby avoiding the introduction of parasitic parameters and problems such as leaks and shorts that can be caused when the top electrode bridge portion 1080 and the bottom electrode bridge portion 1040 overlap. However, preferably, referring to FIG. 2C, the bottom electrode bridge portion 1040 is provided along all sides of the bottom electrode resonance portion 1041 and continuously extends to the substrate at the outer periphery of the cavity 102. , which allows the bottom electrode bridge portion 1040 to extend above some substrates in more directions at the perimeter of the cavity 102, i.e., when the bottom electrode bridge The portion 1040 completely covers the cavity 102 over the part of the cavity in which it is located, so that the laying of the large area bottom electrode bridge portion 1040 provides the effective working area 102A with a supporting force to the membrane layer. to prevent the cavity 102 from collapsing. More preferably, when the bottom electrode bridge portion 1040 extends above a portion of the substrate in more directions at the outer periphery of the cavity 102, the top electrode bridge portion 1080 extends from the outer periphery of the cavity 102. For example, if the top surface shape of the cavity 102 is rectangular, the top electrode bridge portion 1080 extends to the outer periphery of only one side of the cavity 102. , and the bottom electrode bridge portion 1040 extends to the other three sides of the cavity 102, where the top electrode bridge portion 1080 and the bottom electrode bridge portion 1040 and are just connected or separated from each other, i.e., the bottom electrode bridge portion 1040 is then above the portion of the cavity in which it is located. , completely covers the cavity 102 and does not overlap the top electrode bridge portion 1080 in the width direction of the top electrode bridge portion 1080 . Thus, when the top electrode bridge portion 1080 is provided in a large area, it vertically overlaps structures such as the bottom electrode bridge portion 1040, thereby avoiding introducing too many parasitic parameters and improving the electrical performance and reliability of the device. can be further improved.

In each embodiment of the present invention, when the top surface shape of the cavity 102 is polygonal, at least one side of the cavity is exposed from each of the bottom electrode bridge portion 1040 and the top electrode bridge portion 1080, thereby: At least one end of each of the bottom electrode resonance portion 1041 to which the bottom electrode bridge portion 1040 is connected and the top electrode resonance portion 1082 to which the top electrode recess portion 1081 is connected is completely floating. It contributes to the reduction of the area, and also reduces the parasitic parameters such as the parasitic capacitance generated in the invalid area 102B, thereby improving the performance of the device. Preferably, the top electrode recess 1081 is offset from at least the bottom electrode bridge 1040 above the cavity 102 (i.e., they do not overlap in the cavity area), thereby reducing the parasitic Further reduce parasitic parameters such as capacitors to improve device performance.

It should be noted that, in order to achieve an optimal transverse wave blocking effect and contribute to the fabrication of small-sized devices, it is preferable that the top electrode recess 1081 is closer to the effective operating area 102A, and the line width of the top electrode recess 1081 is smaller. , preferably the line width of the top electrode recess 1081 is the minimum line width allowed for the corresponding process, and the top electrode recess 1081 and the effective operating area 102A (that is, the piezoelectric resonance layer 1051) is the minimum distance allowed for the corresponding process.

In each of the above embodiments, the top electrode resonance portion 1082 and the bottom electrode resonance portion 1041 have similar or the same shape and have the same area, or the area of the bottom electrode resonance portion 1041 is the same as that of the top electrode. Although the area of the resonator 1082 is larger, the technical solution of the present invention is not limited to this. In other embodiments of the present invention, the shape of the top electrode resonant portion 1082 and the bottom electrode resonant portion 1041 may not be similar, but the shape of the top electrode recessed portion 1081 may match the shape of the piezoelectric resonant layer 1051 . It is preferable that it matches and can extend along at least one side of the piezoelectric resonance layer 1051 . Furthermore, research has found that most of the parasitic transverse waves in bulk acoustic wave resonators are transmitted through the connecting structure between the film layers on the effective working area 102A and the substrate at the periphery of the cavity, thus , in each embodiment of the present invention, the area (i.e., line width) of the top electrode bridge portion 1080 is minimized, and the area (i.e., line width) of the bottom electrode bridge portion 1040 is minimized, provided that the membrane layers of the effective active area 102A can be effectively supported. The area (ie line width) can be controlled as much as possible.

An embodiment of the invention further provides a filter comprising at least one bulk acoustic wave resonator as described in any of the embodiments of the invention above.

An embodiment of the invention further provides a radio frequency communication system comprising at least one filter according to an embodiment of the invention.

Referring to FIG. 3, one embodiment of the present invention is a method of manufacturing a bulk acoustic wave resonator of the present invention (eg, the bulk acoustic wave resonator shown in FIGS. 1A-2C) comprising:
Step S1 of providing a substrate and forming a first sacrificial layer with a flat top surface on a portion of said substrate;
step S2 of forming a bottom electrode layer on a portion of the first sacrificial layer, the portion positioned on the top surface of the first sacrificial layer extending flatly;
a step S3 of forming a piezoelectric resonance layer on the bottom electrode layer and exposing a portion of the first sacrificial layer and a portion of the bottom electrode layer from the piezoelectric resonance layer;
step S4 of forming a second sacrificial layer having a first groove in a region exposed from the periphery of the piezoelectric resonance layer;
A top electrode layer is formed on the piezoelectric resonance layer and a portion of the second sacrificial layer surrounding the piezoelectric resonance layer, the portion of the top electrode layer covered by the first groove forming a top electrode recess. a step S5 to
removing the second sacrificial layer with the first groove and the first sacrificial layer and forming a cavity at the location of the second sacrificial layer with the first groove and the first sacrificial layer; wherein the top electrode recess is located in the cavity area at the outer circumference of the piezoelectric resonance layer and extends around the piezoelectric resonance layer in the peripheral direction. do.

1A, 1B and 4A-4B, in step S1 of the present embodiment, a process of etching the substrate to form second trenches and filling the second trenches with material forms a first sacrificial layer. A layer is formed on a substrate, and the specific realization process includes the following.

First, referring to FIGS. 1A and 4A, a substrate is provided, specifically a base 100 is provided, and the base 100 is coated with an etching protection layer 101 . The etching protection layer 101 is formed by any suitable process method, such as thermal treatment methods such as thermal oxidation, thermal nitridation, thermal oxynitridation, or deposition methods such as chemical vapor deposition, physical vapor deposition or atomic layer deposition. , may be formed on the base 100 . Moreover, the etching thickness of the protective layer 101 may be reasonably set according to the actual device process needs, and is not specifically limited here.

Subsequently, referring to FIGS. 1A, 1B and 4A, the substrate is etched by a photoetching and etching process to form at least one second groove 102'. The etching process may be a wet etching process or a dry etching process, preferably using a dry etching process, the dry etching process being reactive ion etching (RIE), ion beam etching, plasma etching, or laser cutting. Including but not limited to: The depth and shape of the second groove 102' are all determined by the depth and shape of the cavity required for the bulk acoustic wave resonator to be manufactured, and the cross-sectional shape of the second groove 102' is rectangular. Yes, and in other embodiments of the present invention, the cross-section of the second groove 102' can also be any other suitable shape, such as circular, elliptical, or other polygonal shapes other than rectangular (pentagons, hexagons, etc.). shape.

1A, 1B and 4B, a first sacrificial layer 103 may be filled into the second grooves 102' by a process such as vapor deposition, thermal oxidation, spin coating or epitaxial growth. , the first sacrificial layer 103 may choose a semiconductor material, a dielectric material or a photoresist material different from the base 100 and the etching protection layer 101, for example, if the base 100 is Si-based, the first The sacrificial layer 103 of may be Ge, in which case the first sacrificial layer 103 formed is further covered with the etching protection layer 101 at the periphery of the second groove or the top surface may be higher than the top surface of the etching protection layer 101 around the second trench, and then a chemical mechanical planarization (CMP) process is performed to remove the top of the first sacrificial layer 103 from the etching protection layer 101 , so that the first sacrificial layer 103 is located only in the second groove 102', and the top surface of the first sacrificial layer 103 is aligned with the top surface of the surrounding etching protection layer 101. , thereby providing a flat process surface for subsequent formation of bottom electrode layer 104 having a flat surface.

Referring to FIGS. 1A, 1B and 4C, in step S2, first, an appropriate method is selected according to the material of the bottom electrode to be formed in advance, and the surfaces of the etching protection layer 101 and the first sacrificial layer 103 are etched. A bottom electrode material layer (not shown) may be coated, for example by physical vapor deposition such as magnetron sputtering, evaporation, or chemical vapor deposition methods to form the bottom electrode material layer and then the bottom electrode. A photoresist layer (not shown) in which a pattern is defined is formed on the bottom electrode material layer by a lithographic process, and the bottom electrode material layer is etched using the photoresist layer as a mask to form the bottom electrode layer (i.e., the bottom electrode layer). The remaining bottom electrode material layer) 104 is formed, after which the photoresist layer is removed. The bottom electrode material layer can use any suitable conductive or semiconductor material known in the art, and the conductive material can be a metallic material having electrical conductivity, such as aluminum ( Al), copper (Cu), platinum (Pt), gold (Au), molybdenum (Mo), tungsten (W), iridium (Ir), osmium (Os), rhenium (Re), palladium (Pd), rhodium ( Rh) and ruthenium (Ru), and the semiconductor material is, for example, Si, Ge, SiGe, SiC, SiGeC, or the like. In this embodiment, the bottom electrode layer (remaining bottom electrode material layer) 104 includes a bottom electrode resonance portion 1041 covered by an effective operating region 102A to be formed later, and a first electrode layer from one side of the bottom electrode resonance portion 1041 . The bottom electrode bridge portion 1040 extends to a portion of the etching protection layer 101 outside the second groove 102' via the surface of the sacrificial layer 103, and the bottom electrode resonance portion 1041 is separated from the bottom electrode bridge portion 1040. The outer peripheral portion 1042 of the bottom electrode serves as one metal contact of the bulk acoustic wave resonator to be formed in the region, and the bottom electrode resonant portion 1041 of the bottom electrode bridge portion 1040. It may be connected on the opposite side or may be separate from the bottom electrode bridge portion 1040 as part of the bottom electrode bridge portion of an adjacent bulk acoustic wave resonator, in another embodiment of the invention, The outer periphery 1042 of the bottom electrode may be omitted. The shape of the top surface of the bottom electrode resonance part 1041 may be a pentagon, and in another embodiment of the present invention, it may be a square or a hexagon. is electrically connected to at least one side or at least one corner of the bottom electrode resonance part 1041 via the top surface of the first sacrificial layer 103 outside the bottom electrode resonance part 1041 from the corresponding side of the bottom electrode resonance part 1041 After that, it extends to the top surface of a portion of the etching protection layer 101 on the outer periphery of the second groove 102', and in this embodiment, the top surface of the first sacrificial layer 103 and the etching protection layer Since the top surface of the bottom electrode layer 101 is flush with the top surface of the bottom electrode layer 101, the bottom surface of the bottom electrode layer 104 to be formed can be flush, and the top surface can also be flush. It extends flat in range, ie the bottom electrode resonator portion 1041 and the bottom electrode bridge portion 1040 have a flush bottom surface and a flush top surface. Preferably, as shown in FIG. 2C, the bottom electrode bridge portion 1040 completely covers the cavity 102 above the portion of the cavity in which it is located, and across the width of the top electrode bridge portion 1080: The non-overlapping of the top electrode bridge portion 1080 improves the supporting capacity for subsequent membrane layers, and the overlap of the top electrode bridge portion 1080 avoids introducing unnecessary parasitic parameters as much as possible. The bottom electrode resonator 1041 may be used as an input electrode to receive or provide an electrical signal, such as a radio frequency (RF) signal, or as an output electrode.

1A, 1B and 4C, in step S3, first, piezoelectric material layer 105 is deposited by any suitable method known to those skilled in the art, such as chemical vapor deposition, physical vapor deposition, or atomic layer deposition. Alternatively, a photoresist layer (not shown) having a piezoelectric thin film pattern defined thereon is formed on the piezoelectric material layer 105 by a lithography process, and the photoresist layer is used as a mask to form the piezoelectric material layer 105. is etched to form the piezoelectric resonance layer 1051, after which the photoresist layer is removed. Materials of the piezoelectric material layer 105 are aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), lithium niobate (LiNbO ₃ ), quartz, and potassium niobate (KNbO ₃ ). Alternatively, piezoelectric materials having a wurtzite crystal structure, such as lithium tantalate (LiTaO ₃ ), and combinations thereof may be used. The piezoelectric material layer 105 includes aluminum nitride (AlN) and may also include rare earth metals, such as at least one of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La). Seeds. In addition, the piezoelectric material layer 105 contains aluminum nitride (AlN) and transition metal (eg, at least one of zirconium (Zr), titanium (Ti), manganese (Mn), and hafnium (Hf)). may include After patterning, the remaining piezoelectric material layer 105 includes a piezoelectric resonant layer 1051 and a piezoelectric outer peripheral portion 1050 that are separated from each other, the piezoelectric resonant layer 1051 being positioned on the bottom electrode resonant portion 1041 and the bottom electrode bridge portion 1040 . is exposed and may be completely or partially covered by the bottom electrode resonator 1041 . The shape of the piezoelectric resonance layer 1051 may be the same as or different from the shape of the bottom electrode resonance portion 1041, and the shape of the upper surface thereof may be a pentagon, a quadrangle, a hexagon, a heptagon, or Other polygons such as octagons are also possible. By forming a gap between the piezoelectric outer peripheral portion 1050 and the piezoelectric resonance layer 1051, a part of the first sacrificial layer 103 above the bottom electrode bridge portion 1040 and around the bottom electrode resonance portion 1041 is exposed, The gap that is formed limits the formation area of the subsequent first sacrificial layer and also provides a flat process surface for the subsequent formation of the second groove, the piezoelectric perimeter 1050 being subsequently formed. Provides separation between the top electrode perimeter and the previously formed bottom electrode perimeter 1042 and also provides a flat process surface for subsequent formation of the second sacrificial layer and the top electrode layer. can do.

Referring to FIGS. 1A, 1B and 4D, in step S4, first, the piezoelectric outer peripheral portion 1050, the piezoelectric resonant layer 1051, and the piezoelectric outer peripheral portion 1050 and the piezoelectric resonant layer are subjected to a suitable process such as a coating process or a vapor deposition process. 1051 may be coated with a second sacrificial layer 106, and the second sacrificial layer 106 can fill the gap between the piezoelectric outer peripheral portion 1050 and the piezoelectric resonance layer 1051, The material of the second sacrificial layer 106 can be amorphous carbon, photoresist, dielectric material (e.g. silicon nitride, silicon oxycarbide, porous material, etc.), or semiconductor material (e.g. polycrystalline silicon, amorphous silicon, germanium ), and the material of the second sacrificial layer 106 is preferably different from that of the first sacrificial layer 103. In the subsequent etching process for forming the first groove 107, The top surface of the first sacrificial layer 103 can be used as an etch stop to further control the depth of the subsequently formed first trenches 107, and then the second sacrificial layer 106 by a CMP process. On the other hand, by performing top planarization, the second sacrificial layer 106 is filled only in the gap between the piezoelectric outer peripheral portion 1050 and the piezoelectric resonant layer 1051, and the piezoelectric outer peripheral portion 1050, the piezoelectric resonant layer 1051 and the second sacrificial layer 1051 are filled. Layer 106 constitutes the flat top surface. In another embodiment of the present invention, the second sacrificial layer 106 on the top surface of the piezoelectric outer periphery 1050 and the piezoelectric resonant layer 1051 is removed by an etch back process, thereby removing the piezoelectric outer periphery 1050 and the piezoelectric resonant layer 1051 . Only the interstices may be filled. Next, the second sacrificial layer 106 is patterned by a lithography process or a combined process of photoetching and etching to form the first grooves 107, and the shape, size and position of the first grooves 107 are determined. , the shape, size, position, etc. of the recessed portion of the top electrode to be formed later are determined. Preferably, the sidewalls of the first groove 107 are sloped sidewalls with respect to the plane in which the piezoelectric resonance layer 1051 lies, and the angle between the sidewalls of the first groove 107 and the top surface of the piezoelectric resonance layer 1051 is Both θ1 and θ2 are less than 45 degrees, which contributes to covering the top electrode recess 1081 with material later, avoiding the occurrence of cuts, and improving thickness uniformity. More preferably, the line width of the first groove 107 is the minimum line width allowed for the corresponding process, and the horizontal distance between the first groove 107 and the piezoelectric resonance layer 1051 is It is the minimum distance allowed, which achieves a favorable shear wave blocking effect and contributes to a reduction in the size of the device. In another embodiment of the present invention, the first groove 107 formed after etching the second sacrificial layer 106 when the first groove 107 and the bottom electrode bridge portion do not overlap vertically at all. The bottom surface is stopped up to a predetermined thickness of the first sacrificial layer 103, and transverse waves in the thickness direction of the piezoelectric resonance layer 1051 can be cut off.

In another embodiment of the present invention, the second sacrificial layer 106 consists of a first sub-sacrificial layer (not shown) and a second sub-sacrificial layer (not shown) which are made of different materials and stacked from bottom to top. (not shown), and by providing the first sub-sacrificial layer and the second sub-sacrificial layer, it is possible to precisely control the etch stop point when subsequently etching and forming the first trench. Furthermore, the recess depth of the subsequently formed top electrode recess 1081 can be precisely controlled, and as can be seen from the above, the thickness of the second sub-sacrificial layer determines the depth of the subsequently formed top electrode recess 1081. The recess depth of the recess 1081 is determined. The following steps may form a second sacrificial layer 106 with a first sub-sacrificial layer, a second sub-sacrificial layer and a first trench 107 . First, a first sub-sacrificial layer is filled in the gap between the piezoelectric resonance layer 1051 and the piezoelectric outer peripheral portion 1050 by vapor deposition or epitaxial growth process, and the material selected as the first sub-sacrificial layer is can be converted to other materials after being processed by some process, in this example, said first sub-sacrificial layer may be a semiconductor material and is processed by a chemical vapor deposition process. At this time, the first sub sacrificial layer not only fills the gap between the piezoelectric resonance layer 1051 and the piezoelectric outer circumference 1050 but also fills the upper surfaces of the piezoelectric resonance layer 1051 and the piezoelectric outer circumference 1050 . and then planarize the top of the first sub-sacrificial layer to the top surfaces of the piezoelectric resonant layer 1051 and the piezoelectric outer perimeter 1050 by a chemical mechanical planarization (CMP) process to form the first sub-sacrificial layer. is positioned only in the gap between the piezoelectric resonance layer 1051 and the piezoelectric outer peripheral portion 1050, and then, based on the material of the first sub-sacrificial layer, one of oxidation treatment, nitridation treatment and ion implantation is performed. By selecting an appropriate surface modification treatment process including at least one type and performing the surface modification treatment on a predetermined thickness of the top portion of the first sub-sacrificial layer, the partial thickness of the first sub-sacrificial layer is converting one sub-sacrificial layer into a second sub-sacrificial layer made of another material, the second sub-sacrificial layer and the rest of the first sub-sacrificial layer therebelow which are not subjected to surface modification treatment, The second sacrificial layer 106 that fills the gap between the piezoelectric resonance layer 1051 and the piezoelectric outer peripheral portion 1050 is formed, and the thickness of the second sub-sacrificial layer is equal to the thickness of the top electrode that needs to be formed later. The depth of the recess 1081 is determined by the depth of the recess, after which the top surface of the filled second sacrificial layer 106 and the top surface of the surrounding piezoelectric resonance layer 1051 may not be flush due to the surface treatment process. Therefore, a chemical mechanical planarization (CMP) process further planarizes the top of the second sub-sacrificial layer to the top surface of the piezoelectric resonance layer 1051. so that the top surface of the second sacrificial layer 106 and the top surface of the surrounding piezoelectric resonant layer 1051 are again flush, thereby providing a flat operating surface for subsequent processes. do. Next, a combined photo-etching and etching process is used to remove a second sub-sacrificial layer at the periphery of the effective operating area (102A in FIG. 4F) of the bulk acoustic wave resonator to be fabricated corresponding to the second sacrificial layer 106. The etching may be stopped to the top surface of the first sub-sacrificial layer, and the etching may be stopped to the first sub-sacrificial layer and then to form the first grooves 107 . Overetching may be present.

1A, 1B and 4E, in step S5, first, based on the material of the pre-formed top electrode, select an appropriate method, and A top electrode material layer (not shown) may be coated on the sacrificial layer 106 and the surfaces of the first grooves 107, for example, by physical vapor deposition, such as magnetron sputtering deposition, or by chemical vapor deposition methods. An electrode material layer may be formed, the top electrode material layer may be uniform in thickness at each location, and then a photoresist layer (not shown) having a top electrode pattern defined thereon is subjected to a lithography process. on the top electrode material layer, and using the photoresist layer as a mask, etching the top electrode material layer to form the top electrode layer (i.e., the patterned top electrode material layer or the remaining top electrode material layer ) 108, after which the photoresist layer is removed. The top electrode material layer may use any suitable conductive or semiconducting material known in the art, and the conductive material may be a metallic material having electrical conductivity, such as Al, Cu, Pt, Au, Mo, W, Ir, Os, Re, Pd, Rh and Ru, etc., and the semiconductor material is, for example, Si, Ge, SiGe, SiC, SiGeC, etc. is. In this embodiment, the top electrode layer 108 includes a top electrode resonant portion 1082 coated on the piezoelectric resonant layer 1051, a top electrode recessed portion 1081 coated on the first groove 107, and a top electrode recessed portion 1081. , a top electrode bridge portion 1080 extending through the top surface of a portion of the second sacrificial layer 106 and onto the piezoelectric outer peripheral portion 1050 outside the top electrode recess portion 1081, a top electrode resonance portion 1082, and It includes a top electrode recess 1081 and a top electrode perimeter 1083 which are both separated, the top electrode perimeter 1083 serving as one metal contact for the bulk acoustic wave resonator to be formed in the region. It may be connected to one side of the bridge portion 1080 facing away from the top electrode resonator portion 1082, or may be separated from the top electrode bridge portion 1080 as part of the top electrode bridge portion of the adjacent bulk acoustic wave resonator. However, in other embodiments of the invention, the perimeter 1083 of the top electrode may be omitted. The shape of the top surface of the top electrode resonance part 1082 may be the same as or different from the shape of the piezoelectric resonance layer 1051. The shape of the top surface is, for example, a pentagon. The area of the top electrode resonator 1082 is preferably larger than the piezoelectric resonator layer 1051 so as to be completely sandwiched between the electrode resonator 1041, thereby contributing to the reduction of device size and parasitic parameters. In other embodiments of the present invention, the shape of the top electrode resonator 1082 may also be polygonal, such as square, hexagon, heptagon, or octagon. The top electrode layer 108 may be used as an input electrode for receiving or providing electrical signals, such as radio frequency (RF) signals, or as an output electrode. For example, when bottom electrode layer 104 is used as an input electrode, top electrode layer 108 may be used as an output electrode, and when bottom electrode layer 104 is used as an output electrode, top electrode layer 108 may be used as an input electrode. The piezoelectric resonance layer 1051 converts an electrical signal input via the top electrode resonance section 1082 or the bottom electrode resonance section 1041 into a bulk acoustic wave. For example, the piezoelectric resonant layer 1051 converts electrical signals into bulk acoustic waves by physical vibration. The top electrode recessed portion 1081 is provided along at least one side of the top electrode resonant portion 1082 and connected to the corresponding side of the top electrode resonant portion 1082. It is provided along the side of the top electrode resonance portion 1082 and is provided at least in a region where the top electrode bridge portion 1080 and the top electrode resonance portion 1082 are aligned. A closed ring structure is formed around the entire perimeter of the electrode resonator 1082 (shown in FIGS. 2B and 2C), and for example, the top electrode recess 1081 extends in a plurality of continuous sides of the top electrode resonator 1082. This constitutes an open ring structure (shown in FIG. 2A). The top electrode bridge portion 1080 is electrically connected to the side of the top electrode recess portion 1081 facing away from the top electrode resonance portion 1082, and the top electrode recess portion 1081 is partially connected to the second sacrificial layer. 106 to the top surface of a portion of the etching protection layer 101 outside the second groove 102', and the top electrode bridge portion 1080 and the bottom electrode bridge portion 1040 are separated from each other. , offset from each other (i.e., they do not overlap in the region of the cavity 102), and at least one side of the second groove 102' is exposed from each of the top electrode bridge portion 1080 and the bottom electrode bridge portion 1040. . In one embodiment of the present invention, referring to FIGS. 1A and 2A, in a direction perpendicular to the bottom surface of the second groove 102′, the top electrode recess 1081 is aligned with the bottom electrode resonance of the bottom electrode bridge portion 1040. It does not overlap with the side facing the part 1041 . The projections of the top electrode bridge portion 1080 and the bottom electrode bridge portion 1040 on the bottom surface of the second groove 102' are just connected or separated from each other, and the top electrode bridge portion 1080 is: The second groove 102' may extend above a part of the substrate at the outer circumference of only one side.

1A, 1B and 4F, in step S6, the side facing the second groove 102' of the piezoelectric outer periphery 1050 or the bulk is etched by a combined process of photoetching and etching or laser cutting. An open hole that can expose at least one of a portion of the first sacrificial layer 103 or a portion of the second sacrificial layer 106, which may be perforated in the outer periphery of the device region of the acoustic wave resonator. (not shown) are formed, and then the second sacrificial layer 106 and the first sacrificial layer 103 are removed by introducing a gas and/or a chemical solution into the open holes, and further a second sacrificial layer is formed. Re-emptying the trench creates a cavity 102 which was originally occupied by the second sacrificial layer 106 in the space of the second trench 102' and below the top electrode recess 1081. including space. The bottom electrode resonance part 1041, the piezoelectric resonance layer 1051, and the top electrode resonance part 1082, which float above the cavity 102 and are stacked in order, constitute an independent bulk acoustic thin film. The portion where the top electrode resonator 1082 and the cavity 102 overlap each other along the vertical direction is the effective area, defined as the effective actuation area 102A, which allows electrical energy, such as radio frequency signals, to pass through the bottom electrode. When the voltage is applied to the resonance part 1041 and the top electrode resonance part 1082 , due to the piezoelectric phenomenon occurring in the piezoelectric resonance layer 1051 , vibration and resonance occur in the thickness direction (that is, the longitudinal direction) of the piezoelectric resonance layer 1051 , and the cavity 102 The other area of is the ineffective area 102B, which is an area that does not resonate due to the piezoelectric phenomenon even when electrical energy is applied to the top electrode layer 108 and the bottom electrode layer 104 . The bulk acoustic thin film floating above the effective operating area 102A and composed of the bottom electrode resonance part 1041, the piezoelectric resonance layer 1051 and the top electrode resonance part 1082, which are stacked in order, corresponds to the vibration of the piezoelectric phenomenon of the piezoelectric resonance layer 1051. can output a radio frequency signal with a resonance frequency that Specifically, when electrical energy is applied to the top electrode resonance portion 1082 and the bottom electrode resonance portion 1041, the piezoelectric phenomenon occurring in the piezoelectric resonance layer 1051 generates bulk acoustic waves. In this case, the bulk acoustic waves generated are not only the desired longitudinal waves, but also parasitic transverse waves, which are intercepted by the top electrode recess 1081, confined to the effective active area 102A, and propagated to the membrane layers at the periphery of the cavity. , thereby improving the acoustic wave loss due to the propagation of transverse waves to the film layers at the periphery of the cavity, thereby improving the quality factor of the resonator and ultimately improving the performance of the device. be able to.

It should be noted that step S6 may be performed after all membrane layers above the cavity 102 to be formed have been fabricated, thereby subsequently forming the first sacrificial layer 103 and the second sacrificial layer 106. can be used to protect the space where the cavity 102 is located and the film layer structure stacked with the bottom electrode layer 104 to the top electrode layer 108 formed thereon, and after the cavity 102 is formed, subsequent To avoid the risk of cavity collapse caused when performing the process of Also, the open hole formed in step S6 may be left so that subsequent packaging processes such as bonding two substrates can seal the open hole and also seal the cavity 102 .

In addition, in step S1 of the method for manufacturing the bulk acoustic wave resonator of each of the above embodiments, the substrate is etched to form the second groove 102', and the second groove 102' is filled with the first groove 102'. By forming the sacrificial layer 103 on a portion of the substrate, the cavity 102 formed in step S6 is a groove structure whose entire bottom is recessed into the substrate. Not limited. In step S1 of another embodiment of the present invention, by further forming a first sacrificial layer 103 protruding entirely above the substrate by a combined process of film layer deposition and photo-etching and etching, step S6 The cavity 102 formed in the step S1 has a cavity structure protruding from the substrate surface. Specifically, referring to FIGS. First, the etching protection layer 101 on the surface of the base 100 is coated with the first sacrificial layer 103 without forming the grooves 102′ in the provided substrate, and then the first sacrificial layer 103 is formed by a combined photoetching and etching process. The sacrificial layer 103 is patterned to leave only the first sacrificial layer 103 covered on the region 102, and further the first sacrificial layer 103 is formed on a portion of the substrate, the first sacrificial layer 103 comprising: It may be a stepped structure that widens from top to bottom, the top surface of the first sacrificial layer 103 is flat, and the thickness of the first sacrificial layer 103 allows the depth of the cavity 102 to be formed later. be decided. In this embodiment, the corresponding sidewalls of the bottom electrode perimeter 1042, the bottom electrode bridge 1040, the piezoelectric perimeter 1050, the top electrode perimeter 1083, and the top electrode bridge 1080 are formed as protruding first sacrificial layers. 103, and the vertical cross-section must all be a "Z"-shaped structure, and the subsequent steps are the manufacturing method of the bulk acoustic wave resonator of the embodiment shown in FIGS. 4A-4F. are exactly the same as their counterparts in , and will not be described in detail here. At this time, the portion of the bottom electrode layer 104 located above the cavity 102 extends flatly, that is, the portion above the cavity of the bottom electrode bridge portion 1040 (the portion corresponding to the side wall of the first sacrificial layer 103). ) and the top surface of the bottom electrode resonance portion 1041 are flush with each other, and above the cavity of the bottom electrode bridge portion 1040 (not including the portion corresponding to the side wall of the first sacrificial layer 103). and the bottom surface of the bottom electrode resonance portion 1041 are flush with each other.

In the bulk acoustic wave resonator of the present invention, preferably, the bottom electrode bridge portion and the bottom electrode resonator portion are manufactured in the same process by using the manufacturing method of the bulk acoustic wave resonator of the present invention, and the top electrode bridge portion, The top electrode recess and the top electrode resonator are manufactured by the same process, further simplifying the process and reducing the manufacturing cost.

Of course, those skilled in the art can make various changes and modifications to this invention without departing from the spirit and scope of this invention. Thus, it is intended that the present invention include these modifications and variations of the present invention as they fall within the scope of the claims of the present invention and their equivalents.

100 base 101 etch protection layer 102 cavity 102' second groove 102A active active area 102B inactive area 103 first sacrificial layer 104 bottom electrode layer (i.e. remaining bottom electrode material layer)
1040 Bottom electrode bridge portion 1041 Bottom electrode resonance portion 1042 Bottom electrode outer peripheral portion 105 Piezoelectric material layer 1050 Piezoelectric outer peripheral portion 1051 Piezoelectric resonance layer (or referred to as piezoelectric resonance portion)
106 second sacrificial layer 107 first groove 108 top electrode layer (i.e. remaining top electrode material layer)
1080 top electrode bridge portion 1081 top electrode recess portion 1082 top electrode resonance portion 1083 top electrode outer peripheral portion

Claims (17)

A bulk acoustic wave resonator,
a substrate;
A bottom electrode layer provided on the substrate, wherein a cavity is formed between the bottom electrode layer and the substrate, and a portion of the bottom electrode layer located above the cavity extends flat. a bottom electrode layer;
a piezoelectric resonance layer formed on the bottom electrode layer in an upper portion of the cavity;
a top electrode layer formed on the piezoelectric resonance layer, the top electrode layer being located in the region of the cavity on the outer circumference of the piezoelectric resonance layer and recessed in a direction close to the bottom surface of the cavity; a top electrode layer having a top electrode recess extending in a peripheral direction surrounding the piezoelectric resonance layer ;
a piezoelectric outer peripheral portion provided between the bottom electrode layer and the top electrode layer so as to be separated from the piezoelectric resonant layer and positioned on the outer periphery of the piezoelectric resonant layer;
the top electrode recess is a recess positioned between the piezoelectric resonance layer and the piezoelectric outer peripheral portion;
A bulk acoustic wave resonator characterized by: the bottom electrode layer includes a bottom electrode resonance portion and a bottom electrode bridge portion;
the bottom electrode resonant portion has a flat top surface and overlaps the piezoelectric resonant layer;
the bottom electrode bridge portion flatly extends from one side of the bottom electrode resonance portion to above a portion of the substrate on the outer circumference of the cavity,
the top electrode layer further includes a top electrode resonance portion and a top electrode bridge portion;
the top electrode resonant portion has a flat top surface and overlaps the piezoelectric resonant layer;
the top electrode recess extends in a peripheral direction surrounding the top electrode resonance portion and is connected to the top electrode resonance portion;
one end of the top electrode bridge portion is connected to the top electrode recess portion and the other end abuts on the substrate at the outer periphery of the cavity;
2. The bulk acoustic wave resonator of claim 1, wherein the bottom electrode bridge portion and the top electrode bridge portion are offset from each other. 3. The bulk acoustic wave resonator according to claim 2, wherein both the bottom electrode resonator and the top electrode resonator are polygonal. The top electrode recessed portion is provided along a side of the top electrode resonant portion and is provided at least in a region where the top electrode bridge portion and the top electrode resonant portion are aligned. Item 4. The bulk acoustic wave resonator according to item 3. the top electrode recess is mutually offset from at least the bottom electrode bridge above the cavity; or
5. The bulk acoustic wave resonator according to claim 4, wherein said top electrode recess surrounds the entire periphery of said top electrode resonator. the bottom electrode bridge portion and the bottom electrode resonance portion are formed of the same film layer,
3. The bulk acoustic wave resonator according to claim 2, wherein said top electrode recess, said top electrode bridge and said top electrode resonator are formed of the same film layer. Above the portion of the cavity in which the bottom electrode bridge portion is located, the bottom electrode bridge portion completely covers the cavity and does not overlap the top electrode bridge portion in the width direction of the top electrode bridge portion. 4. The bulk acoustic wave resonator according to claim 3, wherein sidewalls of the top electrode recess are inclined with respect to the top surface of the piezoelectric resonance layer;
8. The bulk acoustic wave resonator according to claim 1, wherein the angle between the side wall of said top electrode recess and the top surface of said piezoelectric resonance layer is 45 degrees or less. . 8. The cavity according to any one of claims 1 to 7, wherein the cavity has a second groove structure whose entire bottom is recessed into the substrate, or a cavity structure whose entire protrusion is provided on the surface of the substrate. 2. The bulk acoustic wave resonator according to item 1. A filter comprising at least one bulk acoustic wave resonator according to any one of claims 1-9 . A radio frequency communication system comprising at least one filter according to claim 10. A method of manufacturing a bulk acoustic wave resonator, comprising:
providing a substrate and forming a first sacrificial layer having a flat top surface on a portion of the substrate;
forming a bottom electrode layer on a portion of the first sacrificial layer, the portion located on the top surface of the first sacrificial layer extending flatly;
forming a piezoelectric resonance layer on the bottom electrode layer exposing a portion of the first sacrificial layer and a portion of the bottom electrode layer;
forming a second sacrificial layer having a first groove in an exposed area around the piezoelectric resonance layer;
A top electrode layer is formed on the piezoelectric resonance layer and a portion of the second sacrificial layer around the piezoelectric resonance layer, and a portion of the top electrode layer covering the first groove is used as a top electrode recess. forming;
removing the second sacrificial layer and the first sacrificial layer and forming a cavity at the location of the second sacrificial layer and the first sacrificial layer, wherein the top electrode recess is the piezoelectric located in the region of the cavity at the perimeter of a resonant layer and extending in a peripheral direction surrounding the piezoelectric resonant layer. Forming the first sacrificial layer with a flat top surface on a portion of the substrate comprises etching the substrate to form a second groove in the substrate; forming a layer to fill the second trench to planarize the top surface of the first sacrificial layer; or
Forming the first sacrificial layer on a portion of the substrate comprises coating the first sacrificial layer on the substrate to planarize a top surface of the first sacrificial layer; and forming the first sacrificial layer to protrude from a portion of the substrate by patterning one sacrificial layer. A method for manufacturing a resonator. removing the second sacrificial layer and the first sacrificial layer,
forming at least one open hole exposing at least a portion of the first sacrificial layer or a portion of the second sacrificial layer after forming a top electrode layer;
and removing the second sacrificial layer and the first sacrificial layer by introducing gas and/or chemicals into the open holes. A method for manufacturing a wave resonator. Forming the bottom electrode layer comprises:
depositing a bottom electrode material layer overlying the first sacrificial layer and the substrate at the perimeter of the first sacrificial layer; patterning the bottom electrode material layer to in turn connect bottoms; forming an electrode bridge portion and a bottom electrode resonance portion, wherein the bottom electrode resonance portion and the piezoelectric resonance layer overlap each other, one end of the bottom electrode bridge portion abuts the substrate on the outer periphery of the cavity, and the Bulk acoustic wave according to claim 12 , characterized in that the top surface of the portion of the bottom electrode bridge portion located in the region of the cavity and the bottom electrode resonator portion are made flush with each other. A method for manufacturing a resonator. Forming the top electrode layer comprises:
depositing a top electrode material layer overlying the second sacrificial layer having the first groove and the piezoelectric resonance layer; forming an electrode bridge portion, the top electrode recessed portion, and a top electrode resonant portion, wherein the top electrode resonant portion and the piezoelectric resonant layer overlap, and one end of the top electrode bridge portion is located at the outer periphery of the cavity; 6. The bulk acoustic wave resonator of claim 15 , wherein said top electrode bridge portion and said bottom electrode bridge portion extend above a substrate and are offset from each other. Production method. Both the bottom electrode resonance portion and the top electrode resonance portion are polygonal,
The top electrode recessed portion is provided along a side of the top electrode resonant portion and is provided at least in a region where the top electrode bridge portion and the top electrode resonant portion are aligned. Item 16. A method for manufacturing a bulk acoustic wave resonator according to Item 16 .

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