WO2023173900A1

WO2023173900A1 - Bulk acoustic resonator, filter, and manufacturing methods therefor

Info

Publication number: WO2023173900A1
Application number: PCT/CN2022/143752
Authority: WO
Inventors: 吴明; 杨清华
Original assignee: 苏州汉天下电子有限公司
Priority date: 2022-03-18
Filing date: 2022-12-30
Publication date: 2023-09-21
Also published as: CN114614789A

Abstract

The present invention provides a bulk acoustic resonator, comprising a cavity formed in a substrate or formed in a support layer on the substrate; and a lower electrode, a piezoelectric layer, and an upper electrode. An overlapping region of the lower electrode, the piezoelectric layer, and the upper electrode forms a sandwich structure; the upper surface of the substrate is used as a projection surface, and in the sandwich structure, the projection shape of the lower electrode on the projection surface is not completely overlapped with the projection shape of the cavity on the projection surface; and at least two mutually independent regions are present within the shape of the composite projection of the cavity and the lower electrode on the upper surface of the substrate, the outer contour line of each independent region is formed by part of the contour line of the cavity, and the inner contour line of the independent region is formed by part of the contour line of the lower electrode. According to the resonator, the performance of a device can be improved, the process difficulty is reduced, the product yield is improved, and then the performance of communication equipment is improved.

Description

A bulk acoustic wave resonator, filter and manufacturing method thereof

This application requires the priority of the Chinese patent application submitted to the China Patent Office on March 18, 2022, with the application number 202210268917.4 and the invention title "A bulk acoustic wave resonator, filter, communication equipment and manufacturing method", which The entire contents are incorporated herein by reference.

Technical field

The present disclosure relates to a filter and a manufacturing method thereof, and more particularly, to a communication device with a film bulk acoustic resonator (FBAR) and a manufacturing method thereof.

Background technique

With the development of communication technology, portable and other types of communication equipment include filters for transmitting and/or receiving signals. The filter can use many different types of acoustic resonators depending on the application, such as film bulk acoustic resonators (FBAR), solid-state resonators (SMR), coupled resonator filters (CRF), bulk acoustic resonators ( SBAR) and two-body acoustic resonator (DBAR), etc.

Among existing technologies, thin film bulk acoustic resonators (FBAR) are more suitable for portable communication devices and are compatible with standard integrated manufacturing technologies. Existing thin film bulk acoustic resonators generally include a substrate, a cavity formed in the substrate, a lower electrode, an upper electrode, and a piezoelectric layer sandwiched between the upper and lower electrodes. When an input electrical signal is applied between the upper and lower electrodes, the reverse piezoelectric effect causes the piezoelectric layer to mechanically expand or contract due to polarization of the piezoelectric material. As the input electrical signal changes over time, the expansion and contraction of the piezoelectric layer generates sound waves that propagate in various directions and are converted into electrical signals through the piezoelectric effect.

The development of thin film bulk acoustic resonator structures with high performance, low process difficulty and high yield is expected by the industry.

Contents of the invention

The following provides a brief summary of the disclosure in order to provide a basic understanding of certain aspects of the disclosure. It should be understood that this summary is not an exhaustive overview of the disclosure. It is not intended to identify key or critical parts of the disclosure or to delineate the scope of the disclosure. The purpose is merely to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

According to an aspect of the present disclosure, a bulk acoustic wave resonator is provided, which includes a cavity formed in a substrate or in a support layer formed on the substrate; a lower electrode, a piezoelectric layer and an upper electrode; the overlapping area of the lower electrode, the piezoelectric layer and the upper electrode forms a sandwich structure; with the upper surface of the substrate as the projection surface, in the sandwich structure, the lower electrode is in the The projected shape on the projection surface does not completely coincide with the projected shape of the cavity on the projection surface, and there are at least two of the cavity and the lower electrode within the composite projected shape of the upper surface of the substrate. The independent areas are independent of each other. The outer outline of the independent area is constituted by the partial outline of the cavity, and the inner outline of the independent area is constituted by the partial outline of the lower electrode.

Further, the projection shapes of the shapes of the cavity and the lower electrode on the projection surface are selected from irregular graphics or regular graphics.

Further, the projected shape of the cavity and the projected shape of the lower electrode are both polygonal.

Further, each side of the polygon formed by the projection of the lower electrode intersects two sides of the polygon formed by the projection of the cavity.

Further, each side of the lower electrode has a portion of the upper surface of the substrate that is erected outside the cavity or a portion that is erected outside the cavity on any plane possible on the upper surface of the cavity. part of the upper surface of the support layer.

Further, the regular graphics are selected from triangles, rectangles, pentagons, hexagons and octagons.

Furthermore, compared with the projected shape of the cavity, the projected shape of the lower electrode is rotated clockwise or counterclockwise about its center position as an axis to form a partially covered shape.

Further, each side of the projection shape of the lower electrode and each side of the cavity projection shape form an included angle θ on the projection plane, and its value range is 90°<θ<180°.

Further, the range of the included angle θ is 110°<θ<160°.

Further, the piezoelectric layer has a release hole at a position corresponding to the cavity not covered by the lower electrode.

Further, the projection shapes of the upper electrode and the lower electrode are the same or different.

Further, a passivation layer is further formed on the upper electrode.

According to another aspect of the present disclosure, a method for manufacturing a bulk acoustic wave resonator is provided, which includes: providing a substrate, etching to form a cavity in the substrate, and depositing a sacrificial layer in the cavity, or in the A support layer is deposited on the substrate, a cavity is formed in the support layer by etching, a sacrificial layer is deposited in the cavity, and the sacrificial layer is planarized; a lower electrode layer is deposited, and the lower electrode layer is etched. The electrode layer forms the lower electrode as described in any one of the above: depositing a piezoelectric layer and an upper electrode layer.

Further, deposit a passivation layer, form the passivation layer on the upper electrode, and etch the passivation layer and the upper electrode; or etch the passivation layer, upper electrode layer, and piezoelectric layer. and lower electrode layer.

Further, etching is performed on the piezoelectric layer or the sacrificial layer corresponding to the position of the sacrificial layer that is not covered by the lower electrode to form a release hole, and then the sacrificial layer is removed through the release hole.

According to another aspect of the present disclosure, a filter is provided, which includes at least one bulk acoustic wave resonator as described above.

Further, a mass loading layer is adaptively formed on the upper electrode of at least one of the resonators. Further, a bonding layer is formed.

Further, a cover sheet is bonded to the bonding layer to form a package.

According to another aspect of the present disclosure, a method of manufacturing a filter is provided, wherein the filter includes at least one resonator, and the at least one resonator includes the aforementioned method of manufacturing a resonator.

Further, before depositing the passivation layer, a mass loading layer is further deposited on the upper electrode layer of at least one of the resonators, and a mass loading layer is adaptively formed on the upper electrode layer through a lift-off process.

Further, the mass-loading layer of the multi-layer composite structure is formed through repeated deposition and peeling processes.

Further, the bonding material is deposited and a bonding layer is formed through a lift-off process.

Further, the method includes bonding the bonding layer with a cover sheet.

Further steps include grinding and thinning to complete the package.

According to another aspect of the present disclosure, a communication device is provided, which includes the filter as described above.

The solution of the present disclosure can at least help achieve one of the following effects: reduce the transverse and longitudinal energy leakage of the thin film bulk acoustic resonator (FBAR) during the working process, improve the quality factor and performance of the product, and improve the electromechanical coupling coefficient Kt value. Reduce process difficulty, improve product yield, and reduce manufacturing costs.

Description of the drawings

The specific contents of the present disclosure will be described below with reference to the accompanying drawings, which will help to understand the above and other objects, features and advantages of the present disclosure more easily. The drawings are merely intended to illustrate the principles of the disclosure. The dimensions and relative positions of the elements in the drawings are not necessarily drawn to scale.

Figures 1-3 show a schematic structural diagram of a thin film bulk acoustic resonator (FBAR) in the prior art;

4-6 show schematic diagrams of the structure and process flow of the resonator according to the first embodiment;

Figures 7a-16 show schematic diagrams of the structure and process flow of the resonator according to the first embodiment;

Figures 17-18 show schematic structural diagrams of the resonator according to the second embodiment.

Detailed ways

Figure 1 shows the structure of an existing thin film bulk acoustic resonator, which includes a substrate 1, a cavity 2 formed in the substrate, a lower electrode 3, an upper electrode 5, and a piezoelectric layer 4 sandwiched between the upper and lower electrodes. . The upper and lower electrodes and the piezoelectric layer form a "sandwich" structure. As shown in Figure 2, in the "sandwich" structure, the lower electrode 3 fully covers the cavity 2, resulting in a larger contact area between the "sandwich" structure and the substrate outside the cavity 2 of the thin film bulk acoustic resonator. During the operation of the bulk acoustic wave resonator, a considerable amount of energy leaks outward along the boundary overlap, thus affecting the quality factor and performance of the product.

Further, in order to release the sacrificial layer to form the cavity 2, and in order to reduce the impact of the release hole on the sandwich structure, the release hole 7 needs to be set slightly away from the cavity, as shown in Figure 3, and an additional release channel 6 needs to be added. To extend the release hole 7 into the cavity, this not only increases the difficulty of the process, but also causes the cavity material to be uncleanly released.

In view of the above technical problems, the present disclosure has designed a novel thin film bulk acoustic resonator structure, which can better solve the harmful effects of existing device structure designs on the performance of thin film bulk acoustic resonators, improve filter performance; and reduce process difficulty and improve product yield.

Exemplary disclosures of the present disclosure will be described below with reference to the accompanying drawings. In the interests of clarity and conciseness, not all features that implement the disclosure are described in this specification. It should be understood, however, that many decisions specific to the present disclosure may be made in the development of any such implementation of the present disclosure in order to achieve the developer's specific goals, and that these decisions may vary from one implementation to another. .

Here, it should also be noted that, in order to avoid obscuring the present disclosure with unnecessary details, only device structures closely related to the solutions according to the present disclosure are shown in the drawings, and omitted components not related to the present disclosure. Great other details.

It should be understood that the present disclosure is not limited to the described implementation forms due to the following description with reference to the accompanying drawings. Herein, where feasible, features may be substituted or borrowed between different embodiments, and one or more features may be omitted in an embodiment.

First embodiment

A first embodiment of an acoustic wave filter structure of the present disclosure is shown with reference to Figures 4-6, wherein like reference numerals represent like components. Figure 4 is a top view of the structure of the filter of this embodiment, and Figure 5 is a cross-sectional view along the A-A’ section in Figure 4 .

A substrate 100 is provided, in which an acoustic wave reflection region composed of a cavity 200 is formed. The substrate may be made of materials compatible with the semiconductor process, such as silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), glass, sapphire, alumina _, SiC, etc. The cavity may be formed by etching.

A lower electrode 300 is formed on the substrate 100 to partially cover the sound wave reflection area. The lower electrode 300 may be a single layer or multiple layers. The projection shape of the lower electrode 300 that partially covers the acoustic wave reflection area as a projection plane on the upper surface of the substrate 100 and the projection shape of the cavity 200 on the upper surface of the substrate 100 can be various shapes, and the preferred projection shape is Both are polygons, and the projected shapes do not completely overlap each other. The composite projected shape of the cavity 200 and the lower electrode 300 on the upper surface of the substrate 100 has at least two mutually independent regions B. The independent regions B are respectively formed by the cavity. The partial contour line constitutes the outer contour line 203 of the independent area and the partial contour line of the lower electrode constitutes the inner contour line 302 of the independent area. The outer contour 203 and the inner contour 302 are defined with the center of the composite projection shape as the reference point, that is to say, for the contours constituting the independent area, the distance from the composite projection shape is The one farther from the center is defined as the outer contour 203, and the one closer to the center of the composite projection shape is defined as the inner contour 302.

It should be noted that the composite projection shape of the cavity and the lower electrode on the upper surface of the substrate has at least three mutually independent areas B, which is a more optimal setting, which is the setting of the subsequent release hole, and the cavity filling material The release and clean removal provide faster and more reliable protection.

Further, at least each side of the polygon formed by the projection of the lower electrode intersects with two sides of the polygon formed by the projection of the cavity.

Furthermore, the lower electrode 300 has a portion that is erected on the upper surface of the substrate 100 outside the cavity 200 on the plane where the upper surface of the substrate 100 is located.

It can be understood that the present disclosure does not further limit the sound wave reflection area formed by the cavity 200 and the shape of the lower electrode 300 . The projection shapes of the shapes of the cavity 200 and the lower electrode 300 on the lower surface of the substrate may be irregular figures, or regular polygons such as triangles, rectangles, pentagons, hexagons, and octagons.

Preferably, in the present disclosure, the projection shapes of the cavity 200 and the lower electrode 300 on the lower surface of the substrate 100 are both pentagons, the center positions of their outlines are the same, and the lower electrode 300 is Compared with the pentagon formed by the projection of the cavity 200 on the upper surface of the substrate 100 , the pentagon formed by the projection on the upper surface of the substrate 100 rotates clockwise or counterclockwise with its center position as the axis. A shape is formed that partially covers the projected shape of the cavity. Specifically, as shown in FIG. 6 , each side of the pentagon formed by the projection of the cavity 200 on the upper surface of the substrate 100 and the projection of the lower electrode 300 on the upper surface of the substrate 100 The angle θ formed by each side of the pentagon on the four quadrants of the projection plane where the upper surface of the substrate 100 is located has a value range of 90°<θ<180°. More preferably, the included angle θ has a value range of 110°<θ<160°.

As shown in FIG. 6 , since the cavity 200 is not completely covered by the lower electrode 300 , a release hole 201 can be set vertically in the area of the cavity 200 that is not covered by the lower electrode 300 , without adding an additional release channel. , which can reduce the possibility of unclean release of cavity filling materials, reduce process difficulty, and save economic costs. More importantly, it reduces the horizontal and vertical leakage of resonator/filter energy, improves the quality factor of the product and improves the electromechanical coupling coefficient Kt value.

The piezoelectric layer 400 formed on the lower electrode 300 may also extend to cover the lower electrode 300 , the cavity 200 and the substrate 100 . and an upper electrode 500 disposed on the piezoelectric layer 400. The upper electrode 500 may be a single layer or multiple layers. The upper/lower electrodes may be formed of one or more conductive materials, such as tungsten (W), molybdenum (Mo), iridium (Ir), aluminum (Al), platinum (Pt), ruthenium (Ru), Various metals compatible with semiconductor processes such as niobium (Nb) or hafnium (Hf). The materials of the upper electrode and the lower electrode may be the same or different. The piezoelectric layer 400 may be formed of any piezoelectric material that is compatible with semiconductor processes, such as aluminum nitride (AlN), doped aluminum nitride, or zirconate titanate (PZT). The piezoelectric layer has a release hole at a position corresponding to the cavity not covered by the lower electrode. The overlapping portions of the upper electrode, the piezoelectric layer and the lower electrode above the acoustic wave reflection area constitute a sandwich structure of the acoustic wave resonator.

A mass load 600 is adaptively formed on the upper electrode 500, and then a passivation layer 700 and a bonding layer 900 are formed (see Figure 16). The bonding layer material can be, for example, Au, or other materials suitable for bonding. . Then, the bonding layer 900 and the cap wafer 800 are bonded and thinned to form a device package.

It can be understood that, in the above-mentioned filter device structure, the substrate 100 formed with a sound wave reflection area composed of a cavity 200 is formed on the substrate 100 with a lower electrode layer 300 partially covering the sound wave reflection area. , the piezoelectric layer 400 formed on the lower electrode 300, and the upper electrode 500 provided on the piezoelectric layer 400 constitute a bulk acoustic wave resonator. If necessary, the bulk acoustic wave resonator can be separately deposited with a passivation layer 700 to form an independent device. Based on the filter device structure of the first embodiment of the present disclosure, as shown in Figures 7a-16, its manufacturing method will be further described in detail below.

Step 1: Provide a substrate 100. The selection of the substrate material is as mentioned above and will not be described again here. The substrate mainly plays the role of a supporting carrier. Taking the Si substrate as an example, it has good mechanical robustness and can ensure that it is relatively strong and reliable during processing and packaging.

Step 2: As shown in Figures 7a and 7b, apply photoresist on the substrate 100, expose and etch the substrate 100 to form a cavity 200 with the shape as described above. After forming the cavity A sacrificial layer 202 is conformally deposited on the substrate of the cavity. The sacrificial layer 202 can be selected from phosphosilicate glass, silicon dioxide, amorphous silicon, and other thin film materials that are compatible with the deposition temperature of subsequent films, do not pollute the process system, and have good etching selectivity and chemical polishing properties. Then the sacrificial layer outside the cavity is removed through a planarization process such as CMP, so that the sacrificial layer fills the cavity. The projected shape of the cavity 200 on the upper surface of the substrate may be an irregular figure, or a regular polygon such as a triangle, a rectangle, a pentagon, a hexagon, an octagon, etc.

Step 3: Referring to Figures 8a and 8b, then, form the lower electrode layer on the substrate 100. It should be understood that the material of the lower electrode layer is not limited to the electrode material as mentioned above. Electrode materials with high acoustic impedance and high sound velocity are sufficient. Then, photoresist is coated, and the lower electrode layer is exposed and etched. The shape of the projection of the lower electrode 300 on the upper surface of the substrate can be an irregular shape, or a triangle, a rectangle, a pentagon, or Regular polygons such as hexagons and octagons. The lower electrode 300 also has a connection portion 301 connected to an external circuit.

Step 4: As shown in Figures 9a and 9b, a piezoelectric layer 400 is deposited on the lower electrode 300. The material of the piezoelectric layer can be selected to meet the bandwidth requirements of wireless mobile communication signals for sending and receiving signals, as mentioned above. As mentioned above, materials compatible with the semiconductor process, such as aluminum nitride (AlN) or zirconate titanate (PZT), are preferably considered.

Step 5: As shown in Figures 10a and 10b, an upper electrode material layer 500 is deposited on the piezoelectric layer 400.

Step 6: As shown in Figures 11a and 11b, a mass load layer 600 is deposited on the upper electrode material layer 500. The mass load layer can be Mo, Al, W, etc. Apply glue, expose, develop, and then use a lift-off process (LIFT OFF) on the mass load layer to remove excess mass load layer material, so as to further deposit a mass load on the upper electrode layer of at least one of the resonators. layer. It can be understood that the mass load layer can form a multi-layer composite mass load by repeating the above steps multiple times.

Step 7: Referring to Figures 12a and 12b, further deposit a passivation layer material 700. The passivation layer material may be AlN or other materials.

Step 8: As shown in Figures 13a and 13b, apply photoresist on the passivation layer material, expose, develop, and etch the passivation layer and upper electrode layer to prepare the upper electrode. It can be understood that the lower electrode layer may not be etched in step 3, but when etching the upper electrode, the piezoelectric layer and the lower electrode layer may be etched at the same time, so that it consists of the upper electrode, the lower electrode and the piezoelectric layer. The outline shape and arrangement of the sandwich structure on the projection plane are as described previously. The outline shape of the upper electrode on the projection plane may be the same as the outline shape of the lower electrode on the projection plane.

Step 9: As shown in FIGS. 14a and 14b , etching is performed to form a release hole 201 on the piezoelectric layer 400 corresponding to the position of the sacrificial layer 202 that is not covered by the lower electrode 300 . It can be understood that when the upper electrode layer is etched while the piezoelectric layer and the lower electrode layer are etched, the release hole 201 is formed by etching at the position of the sacrificial layer 202 that is not covered by the lower electrode 300 .

Step 10: Referring to Figures 15a and 15b, the sacrificial layer 202 is removed through the release hole 201 to form the cavity 200. Specifically, depending on the material of the sacrificial layer, oxidation or selective etching may be used to remove the sacrificial layer 202 .

Step 11: As shown in Figure 16, apply photoresist on the substrate with the sacrificial layer removed, and after exposure and development, deposit a bonding material, such as Au. Then, through a lift-off process, the photoresist in other areas and the Au on it are peeled off to form a bonding layer 900, which is then bonded to the cover wafer 800 (cap wafer) through the bonding layer 900.

Step 12: Thin and grind the bonded device to form a package.

It can be understood that the manufacturing method of the bulk acoustic wave resonator can be prepared by referring to the manufacturing method of the above-mentioned filter according to its specific layer structure, and will not be described again here.

Second embodiment

Figures 17-18 illustrate a second embodiment of a structure containing an acoustic resonator of the present disclosure, wherein like reference numerals represent like components.

A substrate 100 is provided. The substrate 100 may be, for example, silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), glass, sapphire, alumina _, SiC, or other materials compatible with the semiconductor process. form.

A support layer 101 is formed on the substrate 100 , and a cavity 200 is formed by etching the support layer 101 to form a sound wave reflection area.

A lower electrode 300 is formed on the support layer 101 to partially cover the sound wave reflection area. The lower electrode 300 may be a single layer or multiple layers. The projection shape of the lower electrode 300 that partially covers the acoustic wave reflection area on the upper surface of the substrate as a projection plane can be the same as the projection shape of the cavity 200 on the upper surface of the substrate as a projection plane. They are of various shapes, preferably polygonal and not completely coincident with each other. The composite projection shape of the cavity and the lower electrode on the upper surface of the substrate has at least two mutually independent regions, and the independent regions The outer contour of the independent region is formed by a partial contour of the cavity, and the inner contour of the independent area is formed by a partial contour of the lower electrode. The outer contour line and the inner contour line are defined with the center of the composite projection shape as the reference point. That is to say, for the contour lines constituting the independent area, they are farther away from the center of the composite projection shape. The far one is defined as the outer contour, and the one closer to the center of the composite projection shape is defined as the inner contour.

It should be noted that the composite projection shape of the cavity and the lower electrode on the upper surface of the substrate has at least three mutually independent areas, which is a more optimal setting, which is the setting of the subsequent release hole and the cavity filling material. The release and clean removal provide faster and more reliable protection.

Further, each side of the polygon formed by the projection of the lower electrode intersects with two sides of the polygon formed by the projection of the cavity.

Furthermore, the lower electrode 300 has a portion that is erected on the upper surface of the support layer 101 on the plane where the upper surface of the support layer 101 is located.

It can be understood that the present disclosure does not further limit the sound wave reflection area formed by the cavity 200 and the shape of the lower electrode 300 . The projection shape of the cavity 200 and the lower electrode 300 on the upper surface of the substrate may be an irregular figure, or a regular polygon such as a rectangle or a pentagon.

Preferably, in the present disclosure, the projection shapes of the cavity 200 and the lower electrode 300 on the upper surface of the substrate are both pentagons, the center positions of their outlines are the same, and the lower electrode 300 is at the same position. Compared with the pentagon formed by the projection of the cavity on the upper surface of the substrate, the pentagon formed by the projection on the surface of the substrate is partially covered by rotating clockwise or counterclockwise with its center position as the axis. form. Specifically, each side of the pentagon formed by the projection of the cavity 200 on the upper surface of the substrate and the sides of the pentagon formed by the projection of the lower electrode 300 on the upper surface of the substrate are located at the corresponding positions. The angle θ formed by the four quadrants of the plane where the upper surface of the substrate is located has a value range of 90°<θ<180°. More preferably, the included angle θ has a value range of 110°<θ<160°.

Furthermore, since the cavity 200 is not completely covered by the lower electrode 300, the release hole 201 can be vertically provided in the area of the cavity 200 that is not covered by the lower electrode 300. There is no need to add an additional release channel, thereby reducing the need for empty space. The possibility of unclean release of cavity filling material reduces process difficulty and saves economic costs. More importantly, it reduces the horizontal and vertical leakage of resonator/filter energy, improves the quality factor of the product and improves the electromechanical coupling coefficient Kt value.

The piezoelectric layer 400 is formed on the lower electrode 300, and the upper electrode 500 is disposed on the piezoelectric layer 400. The upper electrode 500 may be a single layer or multiple layers. The upper/lower electrodes may be formed of one or more conductive materials, such as tungsten (W), molybdenum (Mo), iridium (Ir), aluminum (Al), platinum (Pt), ruthenium (Ru), Various metals compatible with semiconductor processes such as niobium (Nb) or hafnium (Hf). The materials of the upper electrode 500 and the lower electrode 300 may be the same or different. The piezoelectric layer 400 may be formed of any piezoelectric material that is compatible with semiconductor processes, such as aluminum nitride (AlN), doped aluminum nitride, or zirconate titanate (PZT). The piezoelectric layer has a release hole at a position corresponding to the cavity not covered by the lower electrode. The overlapping portions of the upper electrode 500, the piezoelectric layer 400 and the lower electrode 300 above the acoustic wave reflection area constitute a sandwich structure of the acoustic wave resonator.

It can be understood that the projection of the upper electrode 500 and the piezoelectric layer 400 on the substrate 100 in the sandwich structure may fall within the projection of the lower electrode 300 on the substrate 100, or may be with the projection of the lower electrode 300 on the substrate 100. The projection of the lower electrode 300 on the substrate overlaps, etc.

A mass load layer 600 is adaptively formed on the upper electrode 500, and then a passivation layer 700 and a bonding layer 900, such as Au, are formed on the upper electrode/mass load layer. Then, the bonding layer is bonded to the cover wafer (cap wafer) to form a device package.

It can be understood that the substrate 100 in the above filter device structure can be formed into a cavity 200 to form the support layer 101 of the sound wave reflection area, and a lower layer partially covering the sound wave reflection area is formed on the support layer 101. The electrode layer 300, the piezoelectric layer 400 formed on the lower electrode 300, and the upper electrode 500 provided on the piezoelectric layer 400 constitute a bulk acoustic wave resonator. If necessary, the bulk acoustic wave resonator can be separately deposited with a passivation layer 700 to form an independent device.

The main difference between the manufacturing method of the filter structure based on the second embodiment of the present disclosure and that of the first embodiment is that a support layer is introduced into the device. The manufacturing method of the second embodiment is similar to the first embodiment. With reference to FIG. 7a-16, and the fabrication method is further described in detail below with reference to the device structure of Figures 17-18:

Step 2: Form a support layer 101 on the substrate, then apply photoresist, expose and etch the support layer to form a cavity 200 with the shape as described above. A sacrificial layer is conformally deposited on the layer. The sacrificial layer can be selected from phosphosilicate glass, silicon dioxide, amorphous silicon and other thin film materials that are compatible with the deposition temperature of subsequent thin films, do not pollute the process system, and have good etching selectivity and chemical polishing properties. Then, the sacrificial layer outside the cavity is removed through a planarization process such as CMP, so that the sacrificial layer fills the cavity 200 . The projected shape of the cavity 200 on the upper surface of the substrate may be an irregular figure, or a regular polygon such as a triangle, a rectangle, a pentagon, a hexagon, an octagon, etc.

Step 3: Then, deposit the lower electrode layer on the support layer 101. It should be understood that the material of the lower electrode layer is not limited to the electrode material as mentioned above. It is an electrode with high acoustic impedance and high acoustic velocity. Materials are enough. Then, photoresist is coated, and the lower electrode layer is exposed and etched to form a lower electrode 300. The shape of the lower electrode 300 projected onto the upper surface of the substrate may be an irregular pattern, a triangle, or a rectangle. , pentagon, hexagon, octagon and other regular polygons. The lower electrode 300 also has a connection portion 301 connected to an external circuit.

Step 4: Deposit and form a piezoelectric layer 400 on the lower electrode 300. The material of the piezoelectric layer can be selected to meet the bandwidth requirements of wireless mobile communication signals for sending and receiving signals. As mentioned above, it is preferably considered to be compatible with the semiconductor. Process-compatible materials such as aluminum nitride (AlN) or zirconate titanate (PZT).

Step 5: Deposit and form an upper electrode material layer on the piezoelectric layer 400 .

Step 6: Deposit and form a mass load layer on the upper electrode material layer. The mass load layer may be Mo, Al, W, etc. The excess mass loading layer is removed on the mass loading layer through a lift-off process (LIFT OFF) of glue coating, exposure, and development, so as to further deposit a mass loading layer on the upper electrode layer of at least one of the resonators. It can be understood that the mass-loading layer can be formed into a multi-layer composite mass-loading layer 600 by repeating the above steps multiple times. ,

Step 7: Deposit a passivation layer 700 on the mass load layer. The passivation layer may be made of AlN or other materials.

Step 8: Coat photoresist on the passivation layer, expose, develop, and etch the passivation layer, mass loading layer, and upper electrode layer to prepare the upper electrode. The outline shape of the upper electrode on the projection plane may be the same as the outline shape of the lower electrode on the projection plane. It is understood that the lower electrode layer may not be etched in step 3, but when etching the upper electrode, the piezoelectric layer and the lower electrode layer may be etched at the same time, so that the upper electrode, lower electrode and piezoelectric layer overlap. The outline shape and arrangement of the sandwich structure composed of regions on the projection plane are as described above. It can be understood that photoresist can be coated on the passivation layer, exposed, developed, and etched to achieve the preparation of the sandwich structure.

Step 9: Etch to form a release hole 201 at the position of the sacrificial layer not covered by the lower electrode. It can be understood that when the upper electrode layer is etched while the piezoelectric layer and the lower electrode layer are etched, the release hole 201 is formed by etching at the position of the sacrificial layer 202 that is not covered by the lower electrode 300 .

Step 10: Remove the sacrificial layer through the release hole 201 to form the cavity 200 .

Step 11: Coat photoresist on the substrate with the sacrificial layer removed. After exposure and development, deposit bonding material, such as Au. Then, through a lift-off process, the photoresist in other areas and the Au on it are peeled off to form a bonding layer 900, which is then bonded to the cover wafer 800 (cap wafer) through the bonding layer.

Step 12: Thin and grind the bonded devices.

Third embodiment

A filter, which can be used in the field of portable communication devices such as mobile phones, personal digital assistants (PDAs), and electronic game devices. The filter can include any one of the acoustic resonators in the above embodiments. .

The present disclosure has been described above in conjunction with specific embodiments, but those skilled in the art should understand that these descriptions are exemplary and do not limit the scope of the present disclosure. Those skilled in the art can make various variations and modifications to the present disclosure based on the spirit and principles of the disclosure, and these variations and modifications are also within the scope of the disclosure.

Industrial applicability

The thin film bulk acoustic resonator provided by the present disclosure can reduce horizontal and vertical energy leakage during the working process, improve the quality factor and performance of the product, improve the electromechanical coupling coefficient Kt value, reduce process difficulty, improve product yield, and reduce manufacturing costs.

Claims

A bulk acoustic wave resonator including:

a cavity formed in the substrate or in a support layer formed on the substrate;

a lower electrode, a piezoelectric layer and an upper electrode;

The overlapping area of the lower electrode, the piezoelectric layer and the upper electrode forms a sandwich structure;

Using the upper surface of the substrate as the projection surface, in the sandwich structure, the projection shape of the lower electrode on the projection surface does not completely coincide with the projection shape of the cavity on the projection surface, and The cavity and the lower electrode have at least two mutually independent regions within the composite projection shape of the upper surface of the substrate, and the independent regions are respectively constituted by partial outlines of the cavity. The outer contour and the partial contour of the lower electrode constitute the inner contour of the independent region.
The bulk acoustic wave resonator according to claim 1, wherein the projection shapes of the shapes of the cavity and the lower electrode on the projection surface are selected from irregular shapes or regular shapes.
The bulk acoustic wave resonator of claim 2, wherein the cavity projection shape and the lower electrode projection shape are both polygonal.
The bulk acoustic wave resonator according to claim 3, wherein each side of the polygon formed by the projection of the lower electrode intersects two sides of the polygon formed by the projection of the cavity.
The bulk acoustic wave resonator according to claim 4, wherein each side of the lower electrode has a portion or portion draped over the upper surface of the substrate outside the cavity on the plane where the upper surface of the cavity is located. The portion of the upper surface of the support layer outside the cavity.
The bulk acoustic wave resonator according to claim 2, wherein the projected shape of the lower electrode is rotated clockwise or counterclockwise about the center position of the cavity relative to the projected shape of the cavity to form the projected shape. Partially covered form.
The bulk acoustic wave resonator according to claim 3, wherein each side of the projection shape of the lower electrode and each side of the projection shape of the cavity form an included angle θ on the projection plane, and its value range is 90°. <θ<180°.
The bulk acoustic wave resonator according to claim 7, wherein the included angle θ ranges from 110°<θ<160°.
The bulk acoustic wave resonator according to any one of claims 1 to 8, wherein the piezoelectric layer has a release hole at a position corresponding to the cavity not covered by the lower electrode.
A method for manufacturing a bulk acoustic wave resonator, including:

providing a substrate, etching to form a cavity in the substrate, and depositing a sacrificial layer in the cavity, or depositing a support layer on the substrate, etching to form a cavity in the support layer, and depositing a sacrificial layer in the cavity and planarizing the sacrificial layer;

Depositing a lower electrode layer, and etching the lower electrode layer to form the lower electrode according to any one of claims 1-8;

A piezoelectric layer and an upper electrode layer are deposited.
The manufacturing method of claim 10, wherein a passivation layer is further deposited, the passivation layer is formed on the upper electrode, and the passivation layer and the upper electrode are etched; or the passivation is etched. layer, upper electrode layer, piezoelectric layer and lower electrode layer.
The manufacturing method according to claim 10, wherein etching is performed on the piezoelectric layer or sacrificial layer corresponding to the position of the sacrificial layer not covered by the lower electrode to form a release hole, and then the piezoelectric layer or the sacrificial layer is removed through the release hole. Describe the sacrificial layer.
A filter comprising at least one bulk acoustic wave resonator according to claims 1-12.
The filter of claim 13, wherein at least one of said resonators has an adaptively formed mass loading layer on said upper electrode.
The filter of claim 14, wherein a bonding layer is further formed, and a cover sheet is bonded to the bonding layer to form a package.
A method of manufacturing a filter, wherein the filter includes at least one resonator, and the at least one resonator includes the method of manufacturing the resonator of any one of claims 10-12.
The manufacturing method of a filter according to claim 16, wherein before depositing the passivation layer, a mass loading layer is further deposited on the upper electrode layer of at least one of the resonators, and the upper electrode is formed on the upper electrode through a lift-off process. On-layer adaptability forms mass-loaded layers.
The manufacturing method of the filter according to claim 17, wherein the mass loading layer of the multi-layer composite structure is further formed by repeated deposition and stripping processes.
The manufacturing method of claim 18, further comprising depositing a bonding material, forming a bonding layer through a lift-off process, and bonding the bonding layer to a cover sheet.