Grooved BAW resonators, filters and electronic devices

Abstract

Grooved bulk acoustic wave resonator, filter and electronic device. The present invention relates to a bulk acoustic wave resonator, comprising: a substrate; an acoustic mirror; a bottom electrode, arranged on the upper side of the substrate; a top electrode; and a piezoelectric layer, arranged above the bottom electrode and between the bottom electrode and the top electrode, wherein: the area where the acoustic mirror, the bottom electrode, the piezoelectric layer and the top electrode overlap in the thickness direction of the substrate is the effective area of ​​the resonator; the resonator also includes at least one groove, and the groove extends around the effective area. The groove can be arranged on the lower side or upper side of the piezoelectric layer; or the groove can be arranged on the upper side or lower side of the bottom electrode. The present invention also relates to a filter having the resonator, and an electronic device having the above-mentioned filter or resonator.

Description

Technical Field

[0001] Embodiments of the present invention relate to the semiconductor field, and in particular to a bulk acoustic wave resonator, a filter having the resonator, an electronic device having the filter, and a method for increasing the parallel impedance of a resonator. Background Art

[0002] At present, RF front-end filters composed of bulk acoustic wave resonators are widely used in RF communication systems. Such filters usually have excellent electrical properties, such as low insertion loss, steep transition band, large power capacity, strong anti-static discharge ability, and processing technology compatible with IC technology, which is suitable for large-scale low-cost manufacturing. The quality of the filter is closely related to the performance indicators of the resonator.

[0003] BAW resonators generally have two resonant frequencies. The frequency point with the minimum impedance is defined as the series resonant frequency fs, and the corresponding impedance is the series impedance Rs. The frequency point with the maximum impedance is defined as the parallel resonant frequency fp, and the corresponding impedance is the parallel impedance Rp. The piezoelectric conversion efficiency in the resonator is measured by the effective electromechanical coupling coefficient. Usually, the series resonant frequency of the resonator determines the center frequency of the filter, while the effective electromechanical coupling coefficient of the resonator determines the maximum bandwidth that the filter can achieve. The series impedance and parallel impedance of the resonator determine the passband insertion loss and return loss. Generally speaking, the higher the parallel impedance Rp of the resonator and the lower the series impedance Rs, the better the passband insertion loss of the corresponding filter. Therefore, how to improve the performance of the resonator, especially how to improve the parallel impedance Rp of the resonator, is an important and fundamental issue in filter design. Summary of the invention

[0004] The invention proposes a technical solution for increasing the parallel impedance of a bulk acoustic wave resonator by arranging grooves.

[0005] According to one aspect of an embodiment of the present invention, a bulk acoustic wave resonator is proposed, comprising: a substrate; an acoustic mirror; a bottom electrode, arranged on the upper side of the substrate; a top electrode; and a piezoelectric layer, arranged on the upper side of the bottom electrode and between the bottom electrode and the top electrode, wherein: the area where the acoustic mirror, the bottom electrode, the piezoelectric layer, and the top electrode overlap in the thickness direction of the substrate is the effective area of ​​the resonator; the resonator also includes at least one groove, which extends around the edge of the effective area.

[0006] Optionally, the groove is an annular groove.

[0007] Optionally, the lateral distance between the groove and the acoustic mirror remains unchanged.

[0008] Optionally, the at least one groove comprises one groove.

[0009] Optionally, the groove is arranged on the upper side of the substrate and is completely covered by the bottom electrode. Optionally, the depth H of the groove satisfies: 0.1 μm ≤ H ≤ 0.6 μm; and the distance from the groove to the acoustic mirror is D, and the width of the groove is W, wherein: 1 μm ≤ D ≤ 1.8 μm, and 1.2 μm ≤ W ≤ 2.5 μm.

[0010] Optionally, the groove is arranged on the upper side of the substrate and is partially covered by the bottom electrode. Alternatively, the groove is arranged on the upper side of the substrate and is spaced apart from the bottom electrode. Further, the depth H of the groove satisfies the condition: 0.6μm≤H≤1.1μm, or 1.7μm≤H≤2.3μm. Further, 0.7μm≤H≤0.8μm, or 1.9μm≤H≤2.1μm.

[0011] Optionally, the at least one groove includes two grooves.

[0012] Furthermore, the two grooves are arranged on the upper side of the substrate and are completely covered by the bottom electrode.

[0013] Optionally, the two grooves are arranged on the upper side of the substrate and are spaced apart from the bottom electrode.

[0014] Optionally, one of the two grooves is completely covered by the bottom electrode, and the other groove is partially covered by the bottom electrode or is spaced apart from the bottom electrode. Optionally, one of the two grooves is partially covered by the bottom electrode, and the other groove is spaced apart from the bottom electrode.

[0015] Optionally, the groove is arranged on the lower side or the upper side of the piezoelectric layer; or the groove is arranged on the upper side or the lower side of the bottom electrode.

[0016] Optionally, the at least one groove comprises a plurality of groove segments, and the plurality of groove segments are spaced apart from each other and arranged along and around the effective area.

[0017] According to another aspect of the embodiments of the present invention, a filter is provided, comprising the above-mentioned BAW resonator.

[0018] According to yet another aspect of the embodiments of the present invention, an electronic device is provided, comprising the above-mentioned filter or the above-mentioned resonator.

[0019] The present invention also relates to a method for increasing the parallel impedance of a bulk acoustic wave resonator, comprising the steps of: forming at least one annular groove on the upper side of a substrate of the resonator around an effective area of ​​the resonator. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The following description and accompanying drawings may better help understand these and other features and advantages of various embodiments disclosed by the present invention, in which the same reference numerals always represent the same components, wherein:

[0021] Figure 1A is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention, wherein only one annular groove is provided;

[0022] Figure 1B According to an exemplary embodiment of the present invention Figure 1A A cross-sectional view of the BAW resonator along the A-A' direction;

[0023] Figure 1C for Figure 1B An exemplary relationship curve diagram of the depth of the groove (i.e., the height H of the annular pool) and the parallel impedance of the resonator of the bulk acoustic wave resonator in FIG.

[0024] Figure 1D is a cross-sectional view of a bulk acoustic wave resonator according to another exemplary embodiment of the present invention;

[0025] Figure 1E for Figure 1D An exemplary relationship curve diagram of the depth of the groove (i.e., the height H of the annular pool) and the parallel impedance of the resonator of the bulk acoustic wave resonator in FIG.

[0026] Figure 1F is a cross-sectional view of a bulk acoustic wave resonator according to yet another exemplary embodiment of the present invention;

[0027] Figure 1G for Figure 1F An exemplary relationship curve diagram of the depth of the groove (i.e., the height H of the annular pool) and the parallel impedance of the resonator of the bulk acoustic wave resonator in FIG.

[0028] Figure 2A is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention, wherein only two annular grooves are provided;

[0029] Figure 2B According to an exemplary embodiment of the present invention Figure 2A A cross-sectional view of the BAW resonator along the BB' direction;

[0030] Figure 2C is a cross-sectional view of a bulk acoustic wave resonator according to yet another exemplary embodiment of the present invention;

[0031] Figure 2D is a cross-sectional view of a bulk acoustic wave resonator according to yet another exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further specifically described below by examples and in conjunction with the accompanying drawings. In the specification, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be construed as a limitation of the present invention.

[0033] A bulk acoustic wave resonator according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

[0034] Figure 1A is a schematic top view of a bulk acoustic wave resonator according to an exemplary embodiment of the present invention; Figure 1B According to an exemplary embodiment of the present invention Figure 1A Cross-sectional view of the BAW resonator along the AA' direction.

[0035] See also Figure 1A and 1B The BAW resonator includes a bottom electrode 120, a piezoelectric layer 130, a top electrode 140, and a first annular groove 150. The BAW resonator includes a substrate 100 and an acoustic mirror 110, which is located on the upper surface of the substrate or embedded in the substrate. Figure 1B The acoustic mirror is formed by a cavity embedded in the substrate, but any other acoustic mirror structure such as a Bragg reflector is also suitable.

[0036] The bulk acoustic wave resonator also includes a bottom electrode 120, a piezoelectric layer 130, and a top electrode 140. The bottom electrode is deposited on the upper surface of the acoustic mirror and covers the acoustic mirror. The two end portions of the bottom electrode 120 can be etched into inclined surfaces, and the inclined surfaces are located outside the acoustic reflector. In addition, they can be stepped, vertical or other similar structures. The piezoelectric layer 130 has a first end and a corresponding second end and a middle part, and is located on the bottom electrode, and the two end portions extend to the substrate in opposite directions. The top electrode 140 is deposited on the piezoelectric layer 130. The annular groove 150 is located on both sides of the acoustic mirror 110, with a certain spacing from the acoustic mirror, and in the non-slope area at the bottom of the bottom electrode.

[0037] The area where the top electrode, piezoelectric layer, bottom electrode, and cavity overlap in the thickness direction is the effective area of ​​the resonator, that is, area d2 in the figure. When the sound wave leaks out from the effective area, it propagates in the surrounding medium in the form of a traveling wave. When the annular groove 150 is added, due to the introduction of the air interface, the acoustic impedance of the air is 0, and the equivalent acoustic impedance of the corresponding area, that is, the area d1 and d3 in the figure, will be lower than the acoustic impedance of the adjacent two sides, thereby forming two impedance mismatching interfaces, so that the sound wave can be reflected at these two interfaces, so that part of the leaked sound wave energy can return to the resonant cavity d2, thereby increasing the parallel impedance Rp.

[0038] The depth of the annular groove may be the same as or different from the depth of the cavity 110. Figure 1B , H is defined as the depth of the annular groove, W is the width of the annular groove, D is the distance between the inner edge of the annular groove and the edge of the cavity, and the distance that the bottom electrode exceeds the cavity is E. The finite element method is used to perform a two-dimensional simulation of the above structure, and the simulation results are shown in the figure. Figure 1C In the simulation, E is set to 5um, and four cases are calculated: W = 1um, D = 1um; W = 1um, D = 2um; W = 2um, D = 1um and W = 2um, D = 1um. Figure 1C The horizontal axis is the depth H of the annular groove, and the vertical axis is the parallel impedance Rp. The case of H = 0 is the case of no groove; Figure 1C It can be seen that when W=2um, D=1um, when H=0.3um, the parallel impedance Rp can reach 2477, an increase of about 250 (about 11.2%).

[0039] Accordingly, in an exemplary embodiment according to the present invention, for the case where the groove is completely covered by the bottom electrode, the depth H of the groove satisfies: 0.1 μm ≤ H ≤ 0.6 μm; and the distance from the groove to the acoustic mirror is D, and the width of the groove is W, wherein: 1 μm ≤ D ≤ 1.8 μm, and 1.2 μm ≤ W ≤ 2.5 μm. In a further embodiment, 0.1 μm ≤ H ≤ 0.6 μm. Furthermore, 1 μm ≤ D ≤ 1.2 μm, and 1.8 μm ≤ W ≤ 2.0 μm.

[0040] The annular groove 150 may also be disposed outside the bottom electrode 120, such as Figure 1D As shown. Figure 1D The structure is simulated, and the simulation results are as follows Figure 1E As shown. In the simulation, E was set to 5um, and three cases were calculated: W=1um, D=5um; W=1um, D=7um; and W=1um, D=9um. In the figure, the horizontal axis is the depth H of the annular groove, and the vertical axis is the parallel impedance Rp. The case of H=0 is the case without an annular groove; in the case of W=1um, D=7um, when H=0.7um, the parallel impedance Rp reaches 2929, an increase of about 700 (about 31.5%). In the case of W=1um, D=9um, when H=2um, the parallel impedance Rp reaches 2977, an increase of about 750 (33.7%).

[0041] Optionally, the end of the bottom electrode 120 is located above the annular groove 150, but does not completely cover the annular groove 150. Figure 1F As shown. Figure 1F The structure is simulated, and the simulation results are as follows Figure 1GAs shown. In the simulation, E was set to 5um, and three cases were calculated: W = 1um, D = 4.25um; W = 1um, D = 4.5um; W = 1um, D = 4.75um. The horizontal axis in the figure is the depth H of the annular groove, and the vertical axis is the parallel impedance Rp. The case of H = 0 is the case without an annular groove; in the case of W = 1um, D = 4.5um, when H = 0.8um, the parallel impedance Rp reaches 3015, an increase of about 790 (about 35.6%). Compare Figure 1C , 1E From the simulation results of 1G, we can see that when the groove width is fixed, such as W=1um, the best effect of improving the parallel impedance Rp can be achieved when the annular groove spans the end of the bottom electrode (the third structural case).

[0042] Accordingly, in an exemplary embodiment according to the present invention, when the groove is not covered by the bottom electrode or is not completely covered by the bottom electrode, the depth H of the groove satisfies the following conditions: 0.6 μm ≤ H ≤ 1.1 μm, or 1.7 μm ≤ H ≤ 2.3 μm. Further, 0.7 μm ≤ H ≤ 0.8 μm, or 1.9 μm ≤ H ≤ 2.1 μm.

[0043] The above description is based on a single groove as an example. Figures 2A-2D The resonator according to the present invention is explained by taking two grooves as an example.

[0044] like Figures 2A-2D As shown, the BAW resonator includes a bottom electrode 220 , a piezoelectric layer 230 , a top electrode 240 , a first annular groove 250 , and a second annular groove 260 .

[0045] Figure 2B In the embodiment shown, the BAW resonator is arranged along Figure 2A The BAW resonator comprises a substrate 200 and an acoustic mirror 210, which is located on the upper surface of the substrate or embedded in the interior of the substrate. Figure 2B The acoustic mirror is formed by a cavity embedded in the substrate, but any other acoustic mirror structure such as a Bragg reflector is also suitable.

[0046] The bulk acoustic wave resonator also includes a bottom electrode 220, a piezoelectric layer 230, and a top electrode 240. The bottom electrode is deposited on the upper surface of the acoustic mirror and covers the acoustic mirror. The two end portions of the bottom electrode 220 can be etched into inclined surfaces, and the inclined surfaces are located outside the acoustic reflector. In addition, they can be stepped, vertical or other similar structures. The piezoelectric layer 230 has a first end and a corresponding second end and a middle part, and is located on the bottom electrode, and the two end portions extend to the substrate in opposite directions. The top electrode 240 is deposited on the piezoelectric layer 230. The first annular groove 250 and the second annular groove 260 are located on both sides of the acoustic mirror 210, with a certain spacing from the acoustic mirror, and in the non-slope area at the bottom of the bottom electrode.

[0047] By setting multiple annular grooves, Figure 1A The embodiment given in the embodiment can form more acoustic impedance mismatching interfaces, thereby reflecting the leakage sound waves back to the effective area multiple times to enhance the parallel impedance Rp of the resonator.

[0048] The first annular groove 250 and the second annular groove 260 may not all be arranged in the non-slope area at the bottom of the bottom electrode. For example, the first annular groove 250 is arranged outside the bottom electrode 220, and the second annular groove 260 is arranged in the slope area at the bottom of the bottom electrode. Figure 2C shown.

[0049] Optionally, the end of the bottom electrode 220 is located above the first annular groove 250 but does not cover the first annular groove 250, and the second annular groove 260 is disposed below the bottom electrode 220. Figure 2D shown.

[0050] Although in the attached Figures 2A-2D In the figure, only two grooves are shown, but three or more grooves may be provided as required, which are all within the protection scope of the present invention.

[0051] Based on the above, the present invention proposes a bulk acoustic wave resonator, comprising:

[0052] Substrate 100 or 200;

[0053] Acoustic mirror 110 or 210;

[0054] The bottom electrode 120 or 220 is disposed on the upper side of the substrate 100 or 200;

[0055] A top electrode 140 or 240; and

[0056] The piezoelectric layer 130 or 230 is disposed on the upper side of the bottom electrode and between the bottom electrode and the top electrode.

[0057] in:

[0058] The area where the acoustic mirror, bottom electrode, piezoelectric layer, and top electrode overlap in the thickness direction of the substrate is the effective area of ​​the resonator;

[0059] The resonator further comprises a groove 150 or 250 or 260, the groove surrounding the active area (at Figure 1A In the example, it can be considered that the edge of the boundary region d2) corresponding to the top electrode 140 is extended.

[0060] In the present invention, a groove structure is processed on, for example, a substrate at one or more edges of the effective area of ​​the resonator. In practice, by selecting a suitable groove size, the sound waves leaked into the substrate can be effectively reflected, thereby effectively improving the parallel impedance Rp value of the resonator.

[0061] The groove is a microgroove structure. In the drawings of the present invention, the groove is an annular groove. However, the groove can also be a plurality of groove segments, which are spaced apart from each other and arranged around the effective area. For example, the groove segment can be arranged Figure 1A One or more groove segments on one or more sides of the effective area of ​​the polygon shown in .

[0062] In the present invention, as shown in the accompanying drawings, in an optional embodiment, the lateral distance between the groove and the acoustic mirror remains unchanged.

[0063] In an exemplary embodiment of the present invention, the grooves are formed on the substrate. However, the present invention is not limited thereto, and the grooves may also be formed on the lower surface of the piezoelectric layer opposite to the substrate, or may be arranged on the upper surface of the piezoelectric layer. Alternatively, the grooves are arranged on the upper side or the lower side of the bottom electrode.

[0064] In the present invention, the groove or the groove segment may be filled with other materials or may not be filled, and all of these are within the protection scope of the present invention.

[0065] In an optional embodiment of the present invention, one of the two grooves is completely covered by the bottom electrode, and the other groove is partially covered by the bottom electrode or is spaced apart from the bottom electrode. Optionally, one of the two grooves is partially covered by the bottom electrode, and the other groove is spaced apart from the bottom electrode.

[0066] In the present invention, the “upper side” in the orientation means a side farther from the substrate in the thickness direction of the resonator, and the “lower side” means a side closer to the substrate in the thickness direction of the resonator.

[0067] Based on the above, an embodiment of the present invention also relates to a filter, comprising the above-mentioned BAW resonator.

[0068] The embodiments of the present invention also relate to an electronic device, including the above-mentioned filter or resonator. It should be noted that the electronic device here includes but is not limited to intermediate products such as RF front-ends and filter amplifier modules, as well as terminal products such as mobile phones, WIFI, and drones.

[0069] Correspondingly, the present invention also proposes a method for improving the parallel impedance of a bulk acoustic wave resonator, comprising the steps of: forming at least one annular groove on the upper side of the substrate of the resonator around the effective area of ​​the resonator.

[0070] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A bulk acoustic wave resonator, comprising: substrate; Acoustic mirror; A bottom electrode, disposed on the upper side of the substrate; Top electrode; and a piezoelectric layer disposed on the upper side of the bottom electrode and between the bottom electrode and the top electrode, in: The area where the acoustic mirror, bottom electrode, piezoelectric layer, and top electrode overlap in the thickness direction of the substrate is the effective area of ​​the resonator; The resonator further comprises at least one groove, wherein the at least one groove is disposed in the substrate and is located on the upper side of the substrate and extends around the edge of the active area; and At a non-connected side of the bottom electrode, the at least one trench includes a trench partially covered by the bottom electrode; The at least one groove is filled with a gas.

2. The resonator according to claim 1, wherein: The groove is an annular groove.

3. The resonator of claim 2, wherein: The lateral distance between the groove and the acoustic mirror remains unchanged.

4. The resonator according to any one of claims 1 to 3, wherein: At a non-connected side of the bottom electrode, the at least one trench includes a trench partially covered by the bottom electrode.

5. The resonator of claim 4, wherein: The depth H of the groove satisfies the following conditions: 0.6 μm≤H≤1.1 μm, or 1.7 μm≤H≤2.3 μm.

6. The resonator of claim 5, wherein: The depth H of the groove satisfies the following conditions: 0.7 μm≤H≤0.8 μm, or 1.9 μm≤H≤2.1 μm.

7. The resonator according to any one of claims 1 to 3, wherein: The at least one groove includes two grooves arranged in the substrate and located on the upper side of the substrate, and at least one of the two grooves is partially covered by the bottom electrode at a non-connected side of the bottom electrode.

8. The resonator of claim 7, wherein: At the non-connected side of the bottom electrode, one of the two trenches is completely covered by the bottom electrode or is spaced apart from the bottom electrode, and the other trench is partially covered by the bottom electrode.

9. The resonator according to any one of claims 1 to 3, wherein: The at least one groove includes a plurality of groove segments that are spaced apart from each other and are disposed around the active area.

10. A filter comprising the BAW resonator according to any one of claims 1 to 9.

11. An electronic device comprising the filter according to claim 10 or the resonator according to any one of claims 1 to 9.

12. A method for increasing the parallel impedance of a bulk acoustic wave resonator, comprising the steps of: At least one annular groove is formed in the substrate of the resonator and on the upper side of the substrate around the effective area of ​​the resonator, the at least one groove is arranged in the substrate and is on the upper side of the substrate and extends around the edge of the effective area, and at the non-connected side of the bottom electrode, the at least one groove includes a groove partially covered by the bottom electrode, and the at least one groove is filled with gas.

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