Film bulk acoustic resonator with low clutter and high Q value

Abstract

The invention discloses a low-clutter high-Q-value film bulk acoustic resonator, which comprises a substrate, a supporting layer, a lower electrode, a piezoelectric layer, an upper electrode, a frequency modulation layer and an air bridge structure, and is characterized in that the air bridge structure is positioned on the inner side of the lower boundary of the upper electrode; the boundary of one side of the air bridge structure in the axial direction is matched with the position of the protrusion on the upper electrode, and the boundary of the other side of the air bridge structure extends out of the boundary of the lower electrode. The air bridge structure extends out of the boundary of the lower electrode, so that the area of a non-effective region of the resonator can be reduced, the parasitic capacitance is reduced, the Q value of the resonator is improved, and the Q value at the position refers to the Q value Qp of the film bulk acoustic wave resonator at a parallel resonance point fp.

Description

Technical Field

[0001] The invention relates to the technical field of acoustic wave resonators, and in particular to a thin film bulk acoustic wave resonator with low noise and high Q value. Background Art

[0002] With the development of wireless communication systems, communications have long entered the 5G era, and the application of bulk acoustic wave devices has gradually become widespread. Among bulk acoustic wave devices, thin film bulk acoustic wave resonators have been more widely used in RF filters due to their excellent characteristics such as low insertion loss, high Q value, and high frequency, and have gradually become a research hotspot for RF filters. As the basic building block of the filter, the resonator needs to meet the characteristics of low noise and high Q value to ensure that the filter designed based on the resonator has excellent characteristics such as small in-band fluctuation, low insertion loss, low phase fluctuation, and high rectangularity.

[0003] As attached Figure 1 The figure shows a two-dimensional plane schematic diagram of an air gap type thin film bulk acoustic wave resonator in the prior art, and the structure of the resonator includes a substrate 1, a first air cavity 2, a support layer 3, a lower electrode 4, a piezoelectric layer 5, an upper electrode 6, and a frequency modulation layer 7. When an electrical signal is applied between the upper electrode 6 and the lower electrode 4, the piezoelectric material in the piezoelectric layer 5 generates a piezoelectric effect due to its piezoelectric characteristics, thereby forming an oscillation caused by an acoustic wave. Since the size of the resonant region of the resonator is limited, even if the first air cavity can suppress the longitudinal acoustic wave energy in the piezoelectric oscillation stack, there are still many transverse RL waves that leak out, thereby affecting the Q value of the resonator. At the same time, due to the existence of the TE-1 mode in the RL wave, the resonator will generate transverse parasitic vibrations in the resonance region, so that the designed thin film bulk acoustic wave resonator has clutter, which greatly reduces the performance of the filter composed of the resonator.

[0004] Therefore, in the field of micro-acoustic devices, in order to design high-performance film bulk acoustic wave filters, it is necessary to suppress the noise of the film bulk acoustic wave resonator and improve the Q value of the film bulk acoustic wave resonator. The Q value here specifically refers to the film bulk acoustic wave resonator at the parallel resonance point f p Q value Q p How to achieve this goal has become a technical problem that technical personnel in this field need to solve urgently. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is: how to provide a low-noise and high-Q film bulk acoustic wave resonator that can suppress the noise of the film bulk acoustic wave resonator and improve the Q value of the film bulk acoustic wave resonator.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: A thin film bulk acoustic wave resonator with low noise and high Q value comprises a substrate, a support layer, a lower electrode, a piezoelectric layer, an upper electrode and a frequency modulation layer, characterized in that it also comprises an air bridge structure, wherein the air bridge structure is located on the inner side of the lower boundary of the upper electrode, and the boundary on one side of the axial direction of the air bridge structure is adapted to the protruding position on the upper electrode, and the boundary on the other side extends beyond the boundary of the lower electrode.

[0007] Preferably, the vertical height of the air bridge structure is smaller than the vertical height of the upper electrode at the corresponding position.

[0008] Preferably, a concave-convex structure is provided on the inner side of the upper boundary of the upper electrode, the concave-convex structure and the air bridge structure are merged to form a hybrid structure, and the concave-convex structure includes a multi-layer convex structure and a concave structure sequentially arranged along the axial direction.

[0009] Preferably, the multi-layer protrusion structure is not lower than the upper boundary of the upper electrode, so that the multi-layer protrusion structure is at the same height as the upper electrode or protrudes upward from the upper electrode.

[0010] Preferably, the multi-layer protrusion structure includes two or more protrusions with a vertical height difference, and the widths of the protrusions are the same.

[0011] Preferably, the multi-layer protrusion structure includes a first protrusion and a second protrusion, the vertical height of the first protrusion is greater than the vertical height of the second protrusion, and the recessed structure is located inside the second protrusion.

[0012] Preferably, the vertical height of the second protrusion is half of the vertical height of the first protrusion.

[0013] Preferably, a second air cavity is formed between the second protrusion and the frequency modulation layer at a corresponding position.

[0014] Preferably, the protrusions of the multi-layer protrusion structure, the upper electrode, and the lower electrode are all made of metal materials, and the metal materials used include molybdenum, platinum, aluminum, copper, gold, and tungsten.

[0015] Preferably, the support layer and the frequency modulation layer are both made of high Young's modulus materials, and the high Young's modulus materials used include silicon dioxide, silicon nitride, silicon carbide, aluminum oxide, aluminum nitride or new piezoelectric materials with high dielectric constant and high electromechanical coupling coefficient.

[0016] Compared with the prior art, the present invention has the following advantages: 1. The air bridge structure of the present invention extends beyond the boundary of the lower electrode, which can reduce the area of ​​the ineffective region of the resonator, thereby reducing the parasitic capacitance and improving the Q value of the resonator. The Q value here refers specifically to the value of the thin film bulk acoustic wave resonator at the parallel resonance point f p Q value Qp .

[0017] 2. The concave-convex structure and the air bridge structure of this scheme are integrated to form a hybrid structure, in which the multi-layer convex structure can constitute a Bragg reflection layer, which can enhance the reflection of the lateral sound wave and suppress the leakage of the lateral sound wave, so that the lateral sound wave can be confined within the resonance area, thereby improving the Q value of the resonator; and the concave layer can generate a "piston" mode to suppress the TE-1 mode in the lateral RL wave, thereby suppressing the parasitic vibration generated by the thin film bulk acoustic wave resonator, thereby achieving the effect of suppressing the generation of clutter by the thin film bulk acoustic wave resonator.

[0018] 3. The present invention effectively suppresses the parasitic vibration generated by the TE-1 mode, reduces the area of ​​the ineffective region of the resonator, and reduces the leakage of the lateral wave in the RL wave through the combined effect of multiple protrusions and recessed structures with height differences and an air bridge structure, thereby achieving the purpose of suppressing clutter and improving the Q value.

[0019] 4. The second air cavity formed between the second protrusion and the frequency modulation layer can confine the longitudinal sound wave within the piezoelectric oscillator stack, further enhancing the reflection ability of the longitudinal sound wave, and can also form a Bragg reflection layer in the lateral direction, thereby enabling the thin film bulk acoustic wave resonator to obtain a higher Q value.

[0020] 5. Each protrusion is at the same height as the upper electrode or protrudes upward from the upper electrode, so as to avoid the formation of a second recessed layer. If a second recessed layer is formed, the lateral mode in the resonance region will leak. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the two-dimensional plane structure of an air gap type thin film bulk acoustic resonator in the prior art; Figure 2 is the admittance curve of the air gap type thin film bulk acoustic resonator in the prior art; Figure 3 is a Q value curve of an air gap type thin film bulk acoustic resonator in the prior art; Figure 4 A schematic diagram of a two-dimensional planar structure of a thin film bulk acoustic resonator with low noise and high Q value in Embodiment 1 of the present invention (only an air bridge structure); Figure 5 A schematic diagram of a two-dimensional planar structure of a thin film bulk acoustic wave resonator with low noise and high Q value in Embodiment 1 of the present invention (only a multi-layer structure); Figure 6 A schematic diagram of the two-dimensional planar structure of a thin film bulk acoustic resonator with low noise and high Q value in Embodiment 1 of the present invention (having both an air bridge structure and a multilayer structure); Figure 7A schematic diagram of a two-dimensional planar structure of a thin film bulk acoustic resonator with low noise and high Q value in Embodiment 2 of the present invention (the air bridge structure is not shown); Figure 8 A schematic diagram of a two-dimensional planar structure of a thin film bulk acoustic resonator with low noise and high Q value in Embodiment 3 of the present invention (the air bridge structure is not shown); Fig. 9 The admittance curve of the thin film bulk acoustic resonator with low noise and high Q value of the present invention; Fig.10 It is the Q value curve of the thin film bulk acoustic wave resonator with low noise and high Q value of the present invention.

[0022] Explanation of the accompanying drawings: substrate 1, first air cavity 2, supporting layer 3, lower electrode 4, piezoelectric layer 5, upper electrode 6, frequency modulation layer 7, air bridge structure 8, first protrusion 9, second protrusion 10, recessed structure 11, second air cavity 12, third protrusion 13. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meaning understood by people with general skills in the field to which the present invention belongs.

[0024] The words "first", "second" and similar words used in the patent application specification and claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "a", "an" or "the" and other similar words do not indicate a quantitative limitation, but indicate the existence of at least one. Words such as "include" or "comprise" mean that the elements or objects appearing before "include" or "comprise" cover the features, wholes, steps, operations, elements and / or components listed after "include" or "comprise", and do not exclude the existence or addition of one or more other features, wholes, steps, operations, elements, components and / or their collections. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0025] Embodiment 1: As attached Figure 4As shown, a thin film bulk acoustic wave resonator with low noise and high Q value includes a substrate 1 and a piezoelectric oscillator stack located on the substrate 1, wherein the piezoelectric oscillator stack includes a supporting layer 3, a lower electrode 4, a piezoelectric layer 5, an upper electrode, and a frequency modulation layer 7. A first air cavity 2 recessed toward the substrate 1 is provided between the substrate 1 and the supporting layer 3. The first air cavity 2 confines the longitudinal sound wave within the piezoelectric oscillator stack, so that the thin film bulk acoustic wave resonator with low noise and high Q value provided by the present invention obtains a high Q value.

[0026] The film bulk acoustic wave resonator also includes an air bridge structure 8, which is located inside the lower boundary of the upper electrode, and the boundary of one side of the air bridge structure 8 in the axial direction is adapted to the protruding position on the upper electrode, and the boundary of the other side extends beyond the boundary of the lower electrode, and the vertical height of the air bridge structure 8 is less than the vertical height of the upper electrode at the corresponding position. The air bridge structure 8 extends beyond the boundary of the lower electrode, which can reduce the area of ​​the ineffective region of the resonator, thereby reducing the parasitic capacitance and improving the Q value of the resonator. The Q value here specifically refers to the film bulk acoustic wave resonator at the parallel resonance point f p Q value Q p .

[0027] In this embodiment, a concave-convex structure is provided on the inner side of the upper boundary of the upper electrode 6, and the concave-convex structure and the air bridge structure 8 are combined to form a hybrid structure. The concave-convex structure can exist alone, such as attached Figure 5 As shown, it can also exist together with the air bridge structure 8, as shown in the attached Figure 6 As shown, the concave-convex structure includes a multi-layer convex structure and a concave structure 11 arranged in sequence along the axial direction, and the multi-layer convex structure is not lower than the upper boundary of the upper electrode 6, so that the multi-layer convex structure is equal to the upper electrode 6 or protrudes upward from the upper electrode 6. The multi-layer convex structure includes two or more convexities with a vertical height difference, and the width of each convexity is the same. The multiple convexities in the multi-layer convex structure can constitute a Bragg reflection layer, which can enhance the reflection of the transverse sound wave and suppress the leakage of the transverse sound wave, so that the transverse sound wave can be confined within the resonance region, thereby improving the Q value of the resonator. The Q value here specifically refers to the film bulk acoustic wave resonator at the parallel resonance point f p Q value Q p The recessed structure 11 can generate a "piston" mode to suppress the TE-1 mode in the transverse RL wave, thereby suppressing the parasitic vibration generated by the thin film bulk acoustic wave resonator, and further achieving the effect of suppressing the generation of clutter by the thin film bulk acoustic wave resonator. At the same time, each protruding layer is at the same height as the upper electrode 6 or protrudes upward from the upper electrode 6, so that the formation of a second recessed structure can be avoided. If the second recessed structure is formed, the transverse mode in the resonance area will leak.

[0028] Specifically, the multilayer protrusion structure in this embodiment includes a first protrusion 9 and a second protrusion 10, the vertical height of the second protrusion 10 is less than the vertical height of the first protrusion 9, the recessed structure 11 is located inside the second protrusion 10, and the vertical height of the second protrusion 10 is not less than the vertical height of the upper electrode 6, so as to avoid the formation of a second recessed structure at the upper electrode 6. In this specific embodiment, the vertical height of the second protrusion 10 is half of the vertical height of the first protrusion 9.

[0029] Each protrusion of the multi-layer protrusion structure, the upper electrode 6 and the lower electrode are made of metal materials, and the metal materials used include molybdenum, platinum, aluminum, copper, gold, and tungsten.

[0030] The recessed layer 11, the support layer and the frequency modulation layer 7 are all made of high Young's modulus materials, and the high Young's modulus materials used include silicon dioxide, silicon nitride, silicon carbide, aluminum oxide, aluminum nitride or a new type of piezoelectric material with a high dielectric constant and a high electromechanical coupling coefficient. Specifically, Pb 1-x (Mg 1 / 3 Nb 2 / 3 ) 3-x PbTiO3 (PMN-PT) is used as a new piezoelectric material. The material used in the piezoelectric layer is a piezoelectric material such as aluminum nitride, zinc oxide, PZT, single crystal lithium niobate, and a new piezoelectric material.

[0031] Embodiment 2: As attached Figure 7 As shown, in this specific embodiment, a second air cavity 12 is formed between the second protrusion 10 and the frequency modulation layer 7. The second air cavity 12 can confine the longitudinal sound waves within the piezoelectric oscillation stack, further enhancing the reflection ability of the longitudinal sound waves, and can also form a Bragg reflection layer in the lateral direction, so that the thin film bulk acoustic wave resonator obtains a higher Q value. Of course, the frequency modulation layer can also be directly covered on the upper electrode without forming a second air cavity between the second protrusion. The specific position of the frequency modulation layer is not limited.

[0032] Embodiment three: As attached Figure 8 As shown, in this specific embodiment, the multi-layer protrusion structure includes a first protrusion 9, a second protrusion 10 and a third protrusion 13, wherein the first protrusion 9 and the third protrusion 13 have the same vertical height, the second protrusion 10 has a vertical height less than the first protrusion 9 and the third protrusion 13, and the recessed structure 11 is located inside the third protrusion 13. Of course, in specific use, the protrusions may also be other numbers, which is not specifically limited in this solution.

[0033] As attached Figure 2 The prior art is shown in Figure 1 The admittance curve of the prefix FBAW resonator of air gap type is shown in Figure 1. Fig. 9is the admittance curve of the thin film bulk acoustic wave resonator of the present invention, Figure 2 The parasitic vibration of the prior art air gap type FBAR is mainly manifested at the series resonance point f of the FBAR. s There were noises before, but the thin film bulk acoustic wave resonator with low noise and high Q value provided by the present invention can effectively suppress the noises caused by the TE-1 mode in the RL wave.

[0034] As attached Figure 3 The prior art is shown in Figure 1 The Q value curve of the air gap type film bulk acoustic wave resonator is shown in the figure. Fig.10 The Q value curve of the film bulk acoustic wave resonator of the present invention is as follows. Compared with the air gap film bulk acoustic wave resonator of the prior art, the low-noise high-Q value film bulk acoustic wave resonator provided by the present invention has a Q value Q at the parallel resonance point. p The improvement is quite obvious (23.5846-104.8796), and the increase is as high as 347.8%.

[0035] Therefore, the present invention effectively suppresses the parasitic vibration generated by the TE-1 mode, reduces the area of ​​the ineffective region of the resonator, and reduces the leakage of the lateral wave in the RL wave through the combined effect of multiple raised layers, recessed layers and air bridge structures with height differences, thereby achieving the purpose of suppressing clutter and improving the Q value.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A thin film bulk acoustic wave resonator with low noise and high Q value, comprising a substrate, a support layer, a lower electrode, a piezoelectric layer, an upper electrode and a frequency modulation layer, characterized in that: It also includes an air bridge structure, which is located inside the lower boundary of the upper electrode, and the boundary on one side of the air bridge structure in the axial direction is adapted to the protruding position on the upper electrode, and the boundary on the other side extends beyond the boundary of the lower electrode.

2. The low-noise high-Q film bulk acoustic resonator according to claim 1 is characterized in that: The vertical height of the air bridge structure is smaller than the vertical height of the upper electrode at the corresponding position.

3. The low-noise high-Q film bulk acoustic resonator according to claim 1 is characterized in that: A concave-convex structure is provided inside the upper boundary of the upper electrode. The concave-convex structure and the air bridge structure are merged to form a hybrid structure. The concave-convex structure includes a multi-layer convex structure and a concave structure sequentially arranged along the axial direction.

4. The low-noise high-Q film bulk acoustic resonator according to claim 3 is characterized in that: The multi-layer protrusion structure is not lower than the upper boundary of the upper electrode, so that the multi-layer protrusion structure is at the same height as the upper electrode or protrudes upward from the upper electrode.

5. The low-noise high-Q film bulk acoustic resonator according to claim 3 is characterized in that: The multi-layer protrusion structure includes two or more protrusions with a vertical height difference, and each of the protrusions has the same width.

6. The low-noise high-Q film bulk acoustic resonator according to claim 3 is characterized in that: The multi-layer protrusion structure includes a first protrusion and a second protrusion, the vertical height of the first protrusion is greater than the vertical height of the second protrusion, and the concave structure is located inside the second protrusion.

7. The low-noise high-Q film bulk acoustic resonator according to claim 6 is characterized in that: The vertical height of the second protrusion is half of the vertical height of the first protrusion.

8. The low-noise high-Q film bulk acoustic resonator according to claim 6, characterized in that: A second air cavity is formed between the second protrusion and the frequency modulation layer at a corresponding position.

9. The low-noise high-Q film bulk acoustic resonator according to claim 3, characterized in that: The protrusions of the multi-layer protrusion structure, the upper electrode, and the lower electrode are all made of metal materials, and the metal materials used include molybdenum, platinum, aluminum, copper, gold, and tungsten.

10. The low-noise high-Q film bulk acoustic resonator according to claim 3, characterized in that: The support layer and the frequency modulation layer are both made of high Young's modulus materials, and the high Young's modulus materials used include silicon dioxide, silicon nitride, silicon carbide, aluminum oxide, aluminum nitride or new piezoelectric materials with high dielectric constant and high electromechanical coupling coefficient.

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