Surface Acoustic Wave Resonator and Method of Manufacturing the Same

Abstract

The present invention discloses a surface acoustic wave resonator and a manufacturing method thereof. The surface acoustic wave resonator includes: a substrate and a piezoelectric layer disposed on the substrate; an interdigital transducer disposed on the upper surface of the piezoelectric layer; a first dielectric layer is provided between the gaps of the interdigital transducer, and a first cavity is provided between the lower surface of at least a part of the first dielectric layer and the upper surface of the piezoelectric layer. By providing a first cavity on the side of the first dielectric layer adjacent to the piezoelectric layer in the present invention, the first dielectric layer between the gaps of the interdigital transducer is suspended, so as to reflect the acoustic wave propagating along the surface of the piezoelectric layer to the suspended portion of the first dielectric layer, thereby reducing the loss of the acoustic wave; the first cavity is divided into multiple sub-first cavities by the interdigital transducer, so as to expose the portion of the interdigital transducer adjacent to the surface of the piezoelectric layer to the air, thereby facilitating the elimination of clutter at the boundary of the interdigital transducer, and further improving the overall performance of the resonator.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor device manufacturing, and in particular, to a surface acoustic wave resonator and a manufacturing method thereof. Background Art

[0002] Since the analog radio frequency communication technology was developed in the early 1990s, the radio frequency front-end module has gradually become the core component of communication devices. Among all radio frequency front-end modules, filters have become the components with the strongest growth momentum and the greatest development prospects. With the rapid development of wireless communication technology and the increasing maturity of the 5G communication protocol, more stringent standards have been put forward for all aspects of the performance of radio frequency filters. The performance of a filter is determined by the resonator units that make up the filter. SAW devices (surface acoustic wave devices), with characteristics such as small volume, low insertion loss, large out-of-band rejection, high quality factor, high operating frequency, large power capacity, and good anti-electrostatic shock ability, have become one of the most suitable filters for 5G applications. SAW devices (surface acoustic wave devices) are circuit elements that convert electrical signals into surface waves and perform signal processing, and are widely used as filters, resonators, etc.

[0003] Generally, a surface acoustic wave resonator is made by fabricating two interdigital transducers on the polished surface of a substrate material with piezoelectric properties, serving as a transmitting transducer and a receiving transducer respectively. The transmitting transducer converts the RF signal into a surface acoustic wave, which propagates on the surface of the substrate. After a certain delay, the receiving transducer converts the acoustic signal into an electrical signal for output, and the filtering process is achieved through the piezoelectric conversion from electricity to sound and from sound to electricity.

[0004] However, in the currently fabricated surface acoustic wave resonators, when the acoustic wave between the two interdigital transducers propagates along the surface of the piezoelectric layer, it is easy to spread out, resulting in losses. In addition, when forming the interdigital transducers through an etching process, it is easy to damage the flatness of the surface of the piezoelectric layer, making it impossible to further improve the quality factor (Q) and resulting in a low yield, so it cannot meet the requirements of high-performance radio frequency systems. Summary of the Invention

[0005] The purpose of the present invention is to provide a surface acoustic wave resonator and a manufacturing method thereof, to solve the problem of acoustic wave loss, avoid damaging the flatness of the piezoelectric layer, enhance the structural strength of the resonator, improve the quality factor (Q), and thus improve the overall performance of the device.

[0006] To achieve the above purpose, the present invention provides a manufacturing method of a surface acoustic wave resonator, including:

[0007] A substrate and a piezoelectric layer disposed on the substrate;

[0008] An interdigital transducer disposed on the upper surface of the piezoelectric layer;

[0009] A first dielectric layer is provided between the gaps of the interdigital transducer, and a first cavity is provided between the lower surface of at least a part of the first dielectric layer and the upper surface of the piezoelectric layer.

[0010] The present invention also provides a method for manufacturing a thin film bulk acoustic wave resonator, including:

[0011] Providing a piezoelectric layer;

[0012] Forming a sacrificial layer to cover a first region of the piezoelectric layer;

[0013] Forming a dielectric layer to cover the piezoelectric layer and the sacrificial layer;

[0014] Forming a plurality of longitudinally penetrating cavities in the dielectric layer above the sacrificial layer, and at least a part of the bottom of the cavities extends to the sacrificial layer;

[0015] Removing the sacrificial layer to form a first cavity;

[0016] Forming a conductive material in the cavities to form an interdigital transducer.

[0017] The beneficial effects of the present invention are as follows:

[0018] For the thin film bulk acoustic wave resonator provided by the present invention, by providing a first cavity on one side of the first dielectric layer adjacent to the piezoelectric layer, the first dielectric layer between the gaps of the interdigital transducer is suspended, so as to reflect the acoustic wave propagating along the surface of the piezoelectric layer to the suspended part of the first dielectric layer, thereby reducing the loss of the acoustic wave and further improving the Q value of the resonator.

[0019] Further, the interdigital transducer divides the first cavity into a plurality of sub-first cavities, so as to expose the part of the interdigital transducer adjacent to the surface of the piezoelectric layer to the air, thereby facilitating the elimination of clutter at the boundary of the interdigital transducer and further improving the overall performance of the resonator.

[0020] Further, the height of the first cavity is limited within the range of 0.05 μm to 1 μm. If it is too thin, it is not conducive to the effective release of the sacrificial layer. If it is too thick, it will cause too much outward expansion of the width of the interdigital electrode. Therefore, the thickness can only be limited within a certain range.

[0021] Further, the first group of interdigital transducers is electrically connected through a first conductive bump, and the second group of interdigital transducers is electrically connected through a second conductive bump to electrically connect the first group of interdigital transducers and the second group of transducers, so that the two are respectively used as a transmitting transducer and a receiving transducer, and further realize the conversion between acoustic and electrical signals.

[0022] Further, for the interdigital transducer, a metal material with lower resistivity and better thermal conductivity is used, which can reduce the impedance and enhance the heat conduction; for the dielectric layer, a high thermal conductivity dielectric material is used to facilitate enhancing the thermal conductivity.

[0023] Further, a second dielectric layer is disposed on the outer periphery of the interdigital transducer to support the interdigital transducer.

[0024] In the manufacturing method of the thin film bulk acoustic wave resonator provided by the present invention, a first cavity is formed by forming a sacrificial layer on the piezoelectric layer, so as to facilitate the formation of a thin first cavity, thereby effectively releasing the sacrificial layer and avoiding the excessive outward expansion of the width of the subsequent formed interdigital electrode; the formed first cavity can suspend the dielectric layer between the gaps of the interdigital transducer, thereby reflecting the acoustic wave propagating along the surface of the piezoelectric layer back, thereby reducing the acoustic wave energy consumption. In addition, the boundary of the interdigital transducer adjacent to the piezoelectric layer can be brought into contact with the gas in the first cavity to effectively eliminate the boundary clutter; by first forming a cavity in the dielectric layer and then forming an interdigital transducer in the cavity, the etching of the piezoelectric layer during the formation of the traditional interdigital transducer is avoided, ensuring the flatness of the piezoelectric layer, and the distance between the interdigital transducers is limited by the formed cavity to solve the problem that the traditional etching process cannot achieve a small distance.

[0025] Further, the sacrificial layer is made of α-C material, which is convenient for the subsequent formation of a thin first cavity with a small height.

[0026] Further, when the thickness of the piezoelectric layer is relatively thin, a substrate is bonded under the piezoelectric layer to support the piezoelectric layer and avoid the piezoelectric layer being deformed under pressure during the subsequent formation of the sacrificial layer, the dielectric layer, and the interdigital transducer, thereby ensuring the structural strength of the piezoelectric layer; when the thickness of the piezoelectric layer is relatively thick, the piezoelectric layer can be prevented from being deformed under pressure during the subsequent formation of the sacrificial layer, the dielectric layer, and the interdigital transducer. After the interdigital transducer is formed, the piezoelectric layer is thinned to ensure that the piezoelectric layer has good piezoelectric properties, thereby improving the overall characteristics of the resonator. Description of the Drawings

[0027] Figure 1A A top view of a thin film bulk acoustic wave resonator provided by an example of the present invention;

[0028] Figure 1 is Figure 1A A schematic cross-sectional structure diagram of a thin film bulk acoustic wave resonator along A-A shown;

[0029] Figure 2 A flowchart of the steps of a manufacturing method of a thin film bulk acoustic wave resonator according to an embodiment of the present invention;

[0030] Figures 3 - 10 Schematic structure diagrams corresponding to different steps during the manufacturing process of a manufacturing method of a thin film bulk acoustic wave resonator provided in this embodiment.

[0031] Description of the Reference Numerals:

[0032] 1. Substrate; 11. Support layer; 12. Substrate; 2. Piezoelectric layer; 3. Interdigital transducer; 31. First group of interdigital transducers; 311. First conductive interdigital fingers; 312. First conductor; 32. Second group of interdigital transducers; 321. Second conductive interdigital fingers; 322. Second conductor; 4. Dielectric layer; 41. First dielectric layer; 42. Second dielectric layer; 5. First cavity; 5'. Sacrificial layer; 61. First conductive bump; 62. Second conductive bump; 7. Cavity; 71. First sub-cavity; 72. Second sub-cavity; 91. First cavity body; 92. Second cavity body. Detailed implementation manners

[0033] In the surface acoustic wave resonator currently fabricated, when the acoustic wave between two interdigital transducers propagates along the surface of the piezoelectric layer, it is easily diffused out, resulting in loss. In addition, when the interdigital transducer is formed by etching process, the flatness of the surface of the piezoelectric layer is easily damaged, making the quality factor (Q) unable to be further improved and the yield rate low. Therefore, it cannot meet the requirements of high-performance radio frequency systems.

[0034] To solve the above problems, the present invention provides a surface acoustic wave resonator. By providing a first cavity between the lower surface of a part of the dielectric layer and the upper surface of the piezoelectric layer, the dielectric layer between the interdigital transducers is suspended, so as to solve the problem of acoustic wave loss, and can avoid damaging the flatness of the piezoelectric layer, enhance the structural strength of the resonator, improve the quality factor (Q), and further improve the overall performance of the device.

[0035] The following further elaborates in detail on the surface acoustic wave resonator and its manufacturing method of the present invention with reference to the accompanying drawings and specific embodiments. According to the following description and drawings, the advantages and features of the present invention will be clearer. However, it should be noted that the concept of the technical solution of the present invention can be implemented in various different forms and is not limited to the specific embodiments described herein. The accompanying drawings are all in very simplified forms and use non-precise scales, only for the purpose of conveniently and clearly assisting in explaining the purpose of the embodiments of the present invention.

[0036] In the specification and claims, terms such as "first", "second", etc. are used to distinguish between similar elements and are not necessarily used to describe a specific order or chronological order. It is to be understood that, where appropriate, these terms so used may be interchanged, for example, such that embodiments of the present invention described herein can be operated in an order different from that described or shown herein. Similarly, if the method described herein includes a series of steps, and the order of these steps presented herein is not necessarily the only order in which these steps can be executed, and some of the described steps may be omitted and / or some other steps not described herein may be added to the method. If a component in a certain drawing is the same as a component in other drawings, although these components can be easily recognized in all drawings, for the sake of clearer illustration of the drawings, this specification will not label the reference numerals of all identical components in each drawing.

[0037] Figure 1A The top view of a surface acoustic wave resonator structure provided by an embodiment of the present invention, Figure 1 In which, the left figure is Figure 1A The schematic cross-sectional structure diagram of a thin film bulk acoustic wave resonator along A-A shown in the figure, and the right figure is Figure 1A The schematic cross-sectional structure diagram of a thin film bulk acoustic wave resonator along B-B shown in the figure. Please refer to Figure 1A and Figure 1 , the surface acoustic wave resonator includes:

[0038] A substrate 1 and a piezoelectric layer 2 disposed on the substrate 1;

[0039] An interdigital transducer 3 is disposed on the upper surface of the piezoelectric layer 2;

[0040] A first dielectric layer 41 is provided between the gaps of the interdigital transducer 3, and a first cavity 5 is provided between the lower surface of at least a part of the first dielectric layer 41 and the upper surface of the piezoelectric layer 2.

[0041] In this embodiment, the material of the substrate 1 can be any suitable substrate well-known to those skilled in the art, for example, it can be at least one of the materials mentioned below: silicon (Si), germanium (Ge), silicon germanium (SiGe), silicon carbide (SiC), silicon germanium carbide (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP) or other III / V compound semiconductors.

[0042] In this embodiment, the substrate 1 may be a double-layer structure, that is, the substrate 1 includes a base 12 and a support layer 11. It should be noted that the support layer 11 can be combined with the base by deposition or bonding. The bonding methods include: covalent bonding, adhesive bonding or fusion bonding. The deposition method can be chemical vapor deposition or physical vapor deposition. In other embodiments, the base 12 and the support layer 11 can also be bonded through a bonding layer. The materials of the bonding layer include silicon oxide, silicon nitride, silicon oxynitride, silicon carbonitride or ethyl silicate. In addition, the bonding layer can also use adhesives such as photocurable materials or thermosetting materials, such as die attach film (DAF) or dry film, etc. The material of the base 12 can be the same as that of the substrate 1, and the material of the support layer 11 can be the same as that of the substrate 1 or any suitable dielectric material, including but not limited to one of materials such as silicon oxide, silicon nitride, silicon oxynitride, silicon carbonitride, etc. In other embodiments, the substrate 1 can be a single-layer structure.

[0043] In a possible implementation manner, a second cavity may be provided in the substrate 1, and the interdigital transducer 3 is located above the area surrounded by the second cavity. The second cavity is provided on the side of the substrate 1 adjacent to the piezoelectric layer 2. When the substrate 1 is a double-layer structure, the second cavity is provided on the side of the support layer 11 adjacent to the piezoelectric layer 2 and penetrates part or all of the support layer 11.

[0044] In another possible implementation manner, a Bragg acoustic wave reflection layer may be provided in the substrate 1, and the interdigital transducer is located above the area surrounded by the Bragg acoustic wave reflection layer. Specifically, the Bragg reflection layer structure includes a first acoustic impedance layer and a second acoustic impedance layer stacked in sequence. The impedance of the first acoustic impedance layer and the second acoustic impedance layer is different, and the thicknesses of the first acoustic impedance layer and the second acoustic impedance layer are both odd multiples of a quarter of the acoustic wave wavelength.

[0045] A piezoelectric layer 2 is provided above the substrate 1. The piezoelectric layer 2 can be combined with the substrate 1 by bonding or deposition. It should be noted that the bonding method and the deposition method can refer to the bonding or deposition method of the support layer 11 and the base 12 above. In addition, the piezoelectric layer 2 and the substrate 1 can also be bonded through a bonding layer. The material of the bonding layer refers to the bonding layer above and will not be elaborated here.

[0046] The material of the piezoelectric layer 2 can use piezoelectric materials with a wurtzite crystal structure such as aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), lithium niobate (LiNbO3), quartz, potassium niobate (KNbO3), or lithium tantalate (LiTaO3), and combinations thereof. When the piezoelectric layer 2 includes aluminum nitride (AlN), the piezoelectric layer 2 may further include a rare earth metal, such as at least one of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La). In addition, when the piezoelectric layer 2 includes aluminum nitride (AlN), the piezoelectric layer 2 may further include a transition metal, such as at least one of zirconium (Zr), titanium (Ti), manganese (Mn), and hafnium (Hf). Any suitable method well known to those skilled in the art, such as chemical vapor deposition, physical vapor deposition, or atomic layer deposition, can be used to deposit and form the piezoelectric layer.

[0047] An interdigital transducer 3 is provided on the piezoelectric layer 2. The interdigital transducer 3 includes: a first group of interdigital transducers 31 and a second group of interdigital transducers 32. In this embodiment, the first group of interdigital transducers 31 can be used as a transmitting transducer to convert a radio frequency signal into a surface acoustic wave and propagate it on the surface of the piezoelectric layer 2, or can be used as a receiving transducer to convert an acoustic signal into an electrical signal for output. Similarly, the second group of interdigital transducers 32 can also be used as a transmitting transducer or a receiving transducer. When the first group of interdigital transducers 31 is used as a transmitting transducer, the second group of interdigital transducers 32 is used as a receiving transducer, and vice versa. When alternating current is applied to the first group of interdigital transducers 31 and the second group of interdigital transducers 32, the first group of interdigital transducers 31 and the second group of interdigital transducers 32 are respectively used as a transmitting transducer and a receiving transducer and are in a dynamically changing process.

[0048] It should be noted that the lower ends of the first group of interdigital transducers 31 and the second group of interdigital transducers 32 can be in contact or not in contact with the piezoelectric layer 2. When the lower ends of the first group of interdigital transducers 31 and the second group of interdigital transducers 32 are in contact with the piezoelectric layer 2, the acoustic-electric signal conversion effect is the best; when the lower ends of the first group of interdigital transducers 31 and the second group of interdigital transducers 32 are not in contact with the piezoelectric layer 2, the stress generated by the contact of different materials can be avoided.

[0049] Specifically, the first group of interdigital transducers 31 includes at least one first conductive interdigital finger 311, and the second group of interdigital transducers 32 includes at least one second conductive interdigital finger 321. The first conductive interdigital finger 311 and the second conductive interdigital finger 321 are parallel to each other. The first group of interdigital transducers 31 further includes a first conductor 312 facilitating electrical connection, and the second group of interdigital transducers 32 further includes a second conductor 322 facilitating electrical connection. The first conductor 312 is electrically connected to all the first conductive interdigital fingers 311, and the second conductor 322 is electrically connected to all the second conductive interdigital fingers 321. It should be noted that the lower surface of the first conductor 312 may be partially within the boundary of the first cavity 5, partially on the upper surface of the piezoelectric layer 2, or entirely within the boundary of the first cavity 5, or entirely outside the boundary of the first cavity 5; and / or, the lower surface of the second conductor 322 may be partially within the boundary of the first cavity 5, partially on the upper surface of the piezoelectric layer 2, or entirely within the boundary of the first cavity 5, or entirely outside the boundary of the first cavity 5. When part or all of the lower surface of the first conductor 312 is within the boundary of the first cavity 5, the first dielectric layer 41 between the first conductor 312 and the end of the second conductive interdigital finger 321 is suspended, thus avoiding the loss of acoustic waves caused by the first dielectric layer 41 therebetween, and also suppressing the longitudinal clutter on the piezoelectric layer 2. Similarly, when part or all of the lower surface of the second conductor 322 is within the boundary of the first cavity 5, the first dielectric layer 41 between the second conductor 322 and the first conductive interdigital finger 311 is suspended, thus avoiding the loss of acoustic waves caused by the first dielectric layer 41 therebetween, and the longitudinal acoustic waves on the piezoelectric layer 2. When an alternating current is applied to the first group of interdigital transducers 31 and the second group of interdigital transducers 32, acoustic waves are reflected back and forth between adjacent first conductive interdigital fingers 311 and second conductive interdigital fingers 322, forming oscillations.

[0050] Generally, the first conductive interdigital electrode 311 and the second conductive interdigital electrode 321 can be made of any suitable conductive material or semiconductor material well-known to those skilled in the art. Among them, the conductive material can be a metal material with conductive properties. For example, it can be made of one of metals such as molybdenum (Mo), aluminum (Al), copper (Cu), tungsten (W), tantalum (Ta), platinum (Pt), ruthenium (Ru), rhodium (Rh), iridium (Ir), chromium (Cr), titanium (Ti), gold (Au), osmium (Os), rhenium (Re), palladium (Pd), etc., or made of a laminate formed by the above metals. The semiconductor material is, for example, Si, Ge, SiGe, SiC, SiGeC, etc. It should be noted that the interdigital transducer 3 can be formed by deposition, electroplating or etching. The deposition method can be physical vapor deposition such as magnetron sputtering, evaporation, or chemical vapor deposition. The materials of the first group of interdigital transducers 31 and the second group of interdigital transducers 32 can be conductive materials with low impedance, such as one or more of gold, silver, tungsten, platinum, aluminum, and copper. The material of the first conductor 312 is the same as that of the first conductive interdigital electrode 311; and / or, the material of the second conductor 322 is the same as that of the second conductive interdigital electrode 321.

[0051] In this embodiment, a first dielectric layer 41 is provided between the gaps of the interdigital transducer 3. It should be noted that the gap of the interdigital transducer 3 is the gap between adjacent first conductive interdigital electrodes 311 and second conductive interdigital electrodes 321. The first dielectric layer 41 is disposed between adjacent first conductive interdigital electrodes 311 and second conductive interdigital electrodes 321 to space apart the adjacent first conductive interdigital electrodes 311 and second conductive wire interdigital electrodes 321. The material of the first dielectric layer 41 can be selected from high thermal conductivity materials, such as at least one of silicon nitride, silicon carbide, sapphire, silicon dioxide, and aluminum nitride. When the material of the first dielectric layer 41 is silicon carbide or silicon nitride, the thermal conductivity effect is the best.

[0052] The first dielectric layer 41 includes a plurality of sub-dielectric layers. Any sub-dielectric layer is located between adjacent first conductive finger 311 and second conductive finger 322, and adjacent sub-dielectric layers are connected. There is a gap between the first conductor 312 and the second conductive finger 321, and there is a gap between the second conductor 322 and the first conductive finger 311. The number of sub-dielectric layers is determined according to the number of the first conductive finger 311 and the second conductive finger 321. For example, when the number of both the first conductive finger 311 and the second conductive finger 321 is one, the number of sub-dielectric layers is one. For another example, when the number of the first conductive finger 311 is two and the number of the second conductive finger 321 is one, the number of sub-dielectric layers is two. For still another example, when the number of both the first conductive finger 311 and the second conductive finger 321 is two, the number of sub-dielectric layers is three, and so on. In other embodiments, there is no gap between the first conductor 312 and the second conductive finger 321, and there is no gap between the second conductor 322 and the first conductive finger 311, and adjacent sub-dielectric layers are isolated from each other.

[0053] The outer periphery of the interdigital transducer 3 has a second dielectric layer 42, which is disposed on the substrate 1 and connected to the first dielectric layer 41. The second dielectric layer 42 can be formed on the substrate 1 by deposition or bonding, and the material of the second dielectric layer 42 refers to the material of the above-mentioned first dielectric layer 41. In this embodiment, the second dielectric layer 42 and the first dielectric layer 41 can be an integral structure, constituting the dielectric layer 4, and the material of the second dielectric layer 42 is the same as that of the first dielectric layer 41.

[0054] In this embodiment, a first cavity 5 is provided between the lower surface of at least a part of the first dielectric layer 41 and the upper surface of the piezoelectric layer 3. Specifically, a first cavity 5 is provided between the lower surface of at least one sub-dielectric layer and the upper surface of the piezoelectric layer 3; and / or, a first cavity 5 is provided between a part or all of the lower surfaces of the sub-dielectric layers and the upper surface of the piezoelectric layer 3. Taking any sub-dielectric layer as an example, a first cavity 5 is provided between a part of the lower surface of the sub-dielectric layer and the upper surface of the piezoelectric layer 2, so that a part of the lower surface of the sub-dielectric layer is suspended and a part of the lower surface is in contact with the upper surface of the piezoelectric layer 2; or, a first cavity 5 is provided between all of the lower surfaces of the sub-dielectric layer and the upper surface of the piezoelectric layer 2, so that all of the lower surfaces of the sub-dielectric layer are suspended. It should be noted that the above-mentioned sub-dielectric layer is at least one, and when there are at least two sub-dielectric layers, the sub-dielectric layers are adjacent to each other. When the sound wave between the first group of interdigital transducers 31 and the second group of interdigital transducers 32 propagates to the suspended sub-dielectric layer, it can avoid the energy consumption caused by the sound wave being blocked by the sub-dielectric layer at this place, and can also suppress the longitudinal clutter on the piezoelectric layer 2 through the suspended part of the sub-dielectric layer. When there is a first cavity 5 between all of the lower surfaces of all sub-dielectric layers and the upper surface of the piezoelectric layer 2, the effect of reducing sound wave loss is the best.

[0055] The interdigital transducer 3 divides the first cavity 5 into a plurality of first sub-cavities, and adjacent first sub-cavities are isolated from each other or communicate with each other. Specifically, the first conductive interdigital fingers 311 and the second conductive interdigital fingers 321 divide the first cavity 5 into a plurality of first sub-cavities. When the boundary of the cavity 7 extends beyond the boundary of the first cavity 5, adjacent first sub-cavities are isolated from each other. When the boundary of the cavity 7 is within the boundary of the first cavity 5, adjacent first sub-cavities communicate with each other.

[0056] It should be noted that, hereinafter, any adjacent first conductive interdigital finger 311 and second conductive interdigital finger 321 are taken as an example. When at least one end of the first conductive interdigital finger 311 and at least one end of the second conductive interdigital finger 321 are within the boundary range of the first cavity 5, the corresponding adjacent first sub-cavities communicate with each other, and the lower surface of the corresponding first dielectric layer 41 is suspended. It should be noted that there are various situations where at least one end of the first conductive interdigital finger 311 and at least one end of the second conductive interdigital finger 321 are within the boundary range of the first cavity 5. For example, when the end of the first conductive interdigital finger 311 adjacent to the second conductor 322 is within the boundary range of the first cavity 5, both ends or any one end of the second conductive interdigital finger 321 can be within the boundary range of the first cavity 5. Another example is when the end of the first conductive interdigital finger 311 adjacent to the first conductor 312 is within the boundary range of the first cavity 5, and the end of the second conductive interdigital finger 321 adjacent to the first conductor 312 is within the boundary range of the first cavity 5. At this time, the end of the second conductive interdigital finger 321 adjacent to the second conductor 322 may or may not be within the boundary range of the first cavity 5. If the end of the second conductive interdigital finger 321 adjacent to the second conductor 322 is within the boundary range of the first cavity 5, then the end of the first conductive interdigital finger 311 adjacent to the second conductor 322 is also within the boundary range of the first cavity 5. When the ends of the first conductive interdigital finger 311 adjacent to the second conductor 322 and the ends of the second conductive interdigital finger 321 adjacent to the first conductor 312 are not within the boundary range of the first cavity 5, the corresponding adjacent first sub-cavities are isolated from each other, the first dielectric layer 41 falling within the range of the first cavity 5 is suspended, and the lower surface of the first dielectric layer not falling within the range of the first cavity 5 is in contact with the upper surface of the piezoelectric layer 2.

[0057] The first cavity 5 can be a sealed first cavity 5 or the first cavity 5 communicates with the outside world. When part of the boundary of the first cavity 5 extends to the boundary of the dielectric layer 4, the first cavity 5 communicates with the outside world. When all the boundaries of the first cavity 5 are located within the boundary of the dielectric layer 4, the first cavity 5 is isolated from the outside world. Nitrogen, inert gas or air can be filled in the first cavity 5. The height of the first cavity 5 is 0.05um to 1um, or the height ratio of the first cavity 5 to the interdigital transducer 3 is between 1 / 5 and 1 / 2, so as to achieve the effect of cavity formation and reflection, while ensuring the stability of the structure. The cross-sectional shape of the first cavity 5 can be circular, oval or polygonal, and the polygon can be quadrilateral, pentagon, hexagon, etc. In this embodiment, the first cavity 5 can be formed by a sacrificial layer process or an etching process.

[0058] For the convenience of input or output of electrical signals, the surface acoustic wave resonator further includes: a first conductive bump 61 and a second conductive bump 62. The first conductive bump 61 is electrically connected to the first group of interdigital transducers 31, and the second conductive bump 62 is electrically connected to the second group of interdigital transducers 32. The first conductive bump 61 and the second conductive bump 62 are located in the area outside the boundary of the first cavity 5. Specifically, at least part of the first conductive bump 61 is disposed on the first conductor 312 to be electrically connected to the first conductor 312, and at least part of the second conductive bump 62 is disposed on the second conductor 322 to be electrically connected to the second conductor 322, so as to input or output electrical signals to the first group of interdigital transducers 31 and the second group of interdigital transducers 32 through the first conductive bump 61 and the second conductive bump 62 respectively. It should be noted that when part of the first conductive bump 61 is disposed on the first conductor 312, the remaining part of the first conductive bump 61 is located on the second dielectric layer 42, and when part of the second conductive bump 62 is disposed on the second conductor 322, the remaining part of the second conductive bump 62 is located on the second dielectric layer 42. In this embodiment, the material of the first conductive bump 61 can be the same as the material of the first group of interdigital transducers 31; and / or, the material of the second conductive bump 62 can be the same as the material of the second group of interdigital transducers 32.

[0059] In summary, the thin film bulk acoustic wave resonator provided by the present invention opens a first cavity on one side of the dielectric layer adjacent to the piezoelectric layer, so that the first dielectric layer between the gaps of the interdigital transducers is suspended, so as to reflect the acoustic wave propagating along the surface of the piezoelectric layer to the suspended part of the first dielectric layer, thereby reducing the loss of the acoustic wave, and further improving the Q value of the resonator.

[0060] Furthermore, the interdigital transducer divides the first cavity into multiple sub-first cavities, so as to expose the part of the interdigital transducer adjacent to the surface of the piezoelectric layer to the air, so as to facilitate the elimination of clutter at the boundary of the interdigital transducer, and further improve the overall performance of the resonator.

[0061] Further, the height of the first cavity is limited within the range of 0.05 um to 1 um. If it is too thin, it is not conducive to the effective release of the sacrificial layer. If it is too thick, it will cause the width of the interdigital electrode to expand outward too much. Therefore, the thickness can only be limited within a certain range.

[0062] Further, the first group of interdigital transducers is electrically connected through the first conductive bump, and the second group of interdigital transducers is electrically connected through the second conductive bump to energize the first group of interdigital transducers and the second group of transducers, so that the two serve as the transmitting transducer and the receiving transducer respectively, and further realize the conversion between acoustic and electrical signals.

[0063] Further, for the interdigital transducer, a metal material with lower resistivity and better thermal conductivity is used, which can reduce the impedance and enhance the heat conduction; for the dielectric layer, a high thermal conductivity dielectric material is used to facilitate enhancing the thermal conductivity.

[0064] Further, a second dielectric layer is provided on the outer periphery of the interdigital transducer to form a support for the interdigital transducer.

[0065] An embodiment of the present invention provides a manufacturing method of a thin film bulk acoustic resonator. Figure 2 The following is a flowchart of a manufacturing method of a surface acoustic wave resonator provided by an embodiment of the present invention. Please refer to Figure 2 The manufacturing method of the surface acoustic wave resonator includes:

[0066] S01: Provide a piezoelectric layer.

[0067] S02: Form a sacrificial layer to cover the first region of the piezoelectric layer.

[0068] S03: Form a dielectric layer to cover the piezoelectric layer and the sacrificial layer.

[0069] S04: Form a plurality of longitudinally penetrating cavities in the dielectric layer above the sacrificial layer, and the bottom of at least part of the cavities extends to the sacrificial layer.

[0070] S05: Remove the sacrificial layer to form a first cavity.

[0071] S06: Form a conductive material in the cavity to form an interdigital transducer.

[0072] Figures 3 - 10 The following is a schematic structural diagram corresponding to the corresponding steps of the manufacturing method of a thin film bulk acoustic resonator in this embodiment. The following will refer to Figures 3 - 10 The manufacturing method of the thin film bulk acoustic resonator provided in this embodiment will be described in detail.

[0073] Refer to Figure 3 As shown, perform step S01 to provide a piezoelectric layer 2.

[0074] In this embodiment, the piezoelectric layer 2 is a thick piezoelectric wafer with a thickness greater than 0.3 microns. In the subsequent process, it also includes a step of thinning the piezoelectric wafer so that its thickness meets the requirements for generating resonance. In other embodiments, the thickness of the piezoelectric layer 2 is less than 20 microns. At this time, before providing the piezoelectric layer 2, a substrate needs to be provided first, and then a thin piezoelectric layer 2 is deposited on the substrate. The material of the piezoelectric layer 2 refers to that described in the previous structural embodiment and will not be elaborated here.

[0075] Reference Figure 4 , perform step S02 to form a sacrificial layer 5' covering the first region of the piezoelectric layer 2. In this embodiment, for the convenience of forming the interdigital transducer subsequently, the first region is located at the middle position of the resonator.

[0076] In this embodiment, the sacrificial layer 5' is formed on the piezoelectric layer 2 by deposition. Under normal pressure or low pressure conditions at 200 degrees to 400 degrees, the sacrificial layer 5' is formed on the piezoelectric layer 2 by chemical vapor deposition process. Specifically, the thickness of the sacrificial layer 5' is 0.05um - 1um, so that after the subsequent removal of the sacrificial layer 5', a thin first cavity 5 is formed, which is convenient for effectively releasing the sacrificial layer 5' and avoiding the excessive outward expansion of the width of the subsequent formed interdigital electrodes. The material of the sacrificial layer 5' can be α-C to form a thin first cavity 5 with better performance.

[0077] The cross-sectional shape of the sacrificial layer 5' can be circular, elliptical or polygonal, and the polygon can be a quadrilateral, pentagon, hexagon, etc. The sacrificial layer 5' can be strip-shaped or planar. When the sacrificial layer 5' is strip-shaped, the sacrificial layer 5' is distributed along the direction from the first conductive finger to its adjacent second conductive finger. After the subsequent removal of the sacrificial layer 5' to form the first cavity, there is a first cavity between the lower surface of the dielectric layer between adjacent cavities within the first cavity range and the upper surface of the piezoelectric layer 2, and the lower surface of the dielectric layer between adjacent cavities outside the first cavity range is in contact with the upper surface of the piezoelectric layer 2. The number of strip-shaped sacrificial layers 5' can be multiple and parallel to each other. When the sacrificial layer 5' is planar, it is convenient for the subsequent formed cavities to extend to the sacrificial layer 5', so that there is a first cavity between the lower surface of the dielectric layer between adjacent cavities extending to the sacrificial layer 5' and the upper surface of the piezoelectric layer 2, thereby making the dielectric layer suspended. The suspension of the dielectric layer can avoid the blockage of the dielectric layer during the propagation of sound waves, thereby reducing the sound wave loss, and can also suppress the longitudinal clutter of the piezoelectric layer 2.

[0078] In this embodiment, a part of the boundary of the sacrificial layer 5' coincides with the boundary of the dielectric layer or extends beyond the boundary of the dielectric layer to communicate with the outside. After removing the sacrificial layer 5', the first cavity 5 communicates with the outside; alternatively, the boundary of the sacrificial layer 5' is located inside the boundary of the dielectric layer. After removing the sacrificial layer 5', the first cavity 5 is a sealed first cavity 5. It should be noted that when the first cavity 5 communicates with the outside, there is no need to fill gas into the first cavity 5; when the first cavity 5 is a sealed first cavity 5, before forming the interdigital transducer subsequently, nitrogen, inert gas, air, etc. can also be filled into the first cavity 5.

[0079] Reference Figure 5 , perform step S03 to form the dielectric layer 4 to cover the piezoelectric layer 2 and the sacrificial layer 5'.

[0080] The material of the dielectric layer 4 can be selected from high thermal conductivity materials, such as at least one of silicon nitride, silicon carbide, sapphire, silicon dioxide, and aluminum nitride. When the material of the dielectric layer 4 is silicon carbide or silicon nitride, the thermal conductivity effect is the best. The dielectric layer 4 can be formed by a chemical vapor deposition method.

[0081] Perform step S04 to form a plurality of longitudinally penetrating cavities 7 in the dielectric layer 4 above the sacrificial layer 5'. At least a part of the bottom of the cavity 7 extends to the sacrificial layer 5', reference Figure 6 . Among them, the left figure is a schematic cross-sectional structure diagram corresponding to this step along Figure 1A A-A in Figure 1A , and the right figure is a schematic cross-sectional structure diagram corresponding to this step along

[0082] B-B in

[0083] At least a part of the bottom of the cavity 7 extending to the sacrificial layer 5' includes: a part of the bottom of the cavity 7 extends to the sacrificial layer 5' and a part of the bottom extends to the upper surface of the piezoelectric layer 2; or, the entire bottom of the cavity 7 extends to the sacrificial layer 5'. Specifically, when a part of the bottom of the cavity 7 extends to the sacrificial layer 5' and a part of the bottom extends to the upper surface of the piezoelectric layer 2, the lower surface of the interdigital transducer formed in the cavity 7 subsequently is in contact with the upper surface of the piezoelectric layer 2. There is a first cavity between the lower surface of the dielectric layer 4 between the gaps of the interdigital transducer formed in the cavity 7 where a part of the bottom extends to the sacrificial layer 5' and the upper surface of the piezoelectric layer 2, and the lower surface of the dielectric layer 4 between the gaps of the interdigital transducer formed in the cavity 7 where a part of the bottom extends to the upper surface of the piezoelectric layer 2 is in contact with the upper surface of the piezoelectric layer 2. When the entire bottom of the cavity 7 extends to the sacrificial layer 5', the lower surface of the interdigital transducer formed in the cavity 7 is in contact with the upper surface of the piezoelectric layer 2, and there is a first cavity between the lower surface of the dielectric layer 4 between the gaps of the interdigital transducer and the upper surface of the piezoelectric layer 2.

[0083] It should be noted that the number of cavities 7 in the above cases is at least one. When the number is at least two, the cavities 7 are adjacent to each other. When the bottom of at least some of the cavities 7 extends to the sacrificial layer 5', the corresponding cavity 7 communicates with the first cavity formed after the subsequent removal of the sacrificial layer 5'. The suspension of the dielectric layer 4 between adjacent cavities 7 can reduce the blocking of sound waves by the dielectric layer 4, thereby effectively reducing sound wave loss. When the dielectric layer 4 between all adjacent cavities is completely suspended, the effect of reducing sound wave loss is the best.

[0084] The bottom of the cavity 7 extending to the sacrificial layer 5' includes: the bottom of the cavity 7 extending to the upper surface of the sacrificial layer 5' or penetrating the sacrificial layer 5' to extend to the upper surface of the piezoelectric layer 2 or penetrating part of the sacrificial layer 5' to extend into the sacrificial layer 5'. It should be noted that when the bottom of the cavity 7 extends to the sacrificial layer 5', after the subsequent removal of the sacrificial layer 5' to form the first cavity, the cavity 7 can communicate with the first cavity, so as to facilitate the bottom of the subsequently formed interdigital transducer to be connected to the upper surface of the piezoelectric layer 2 to ensure the conversion effect of acoustic and electrical signals.

[0085] In this embodiment, during the formation of the cavity 7, a photoresist is coated on the surface of the dielectric layer 4 to form a photoresist layer; the mask pattern is defined according to the interdigital transducer to be formed subsequently; exposure is performed to transfer the mask pattern structure to the photoresist layer; then the photoresist layer is developed, and the dielectric layer 4 is etched using the developed photoresist layer as a mask to form the cavity 7; the photoresist layer is removed. It should be noted that for the cavity 7 formed in the above manner, the cavity 7 can have a smaller spacing between adjacent cavities 7, and the resonator made thereby has a higher operating frequency and better performance. In addition, the photoresist layer can be removed by using a plasma gas ablation method to avoid damaging the surface of the dielectric layer 4, thereby avoiding affecting the structural characteristics of the subsequently formed interdigital transducer 3.

[0086] In other embodiments, to ensure that the piezoelectric layer 2 is not etched when etching to form the cavity 7, after the formation of the piezoelectric layer 2, a mask layer is further formed on the piezoelectric layer 2. The mask layer exposes part of the surface of the piezoelectric layer 2. The sacrificial layer 5' is deposited on the piezoelectric layer 2 or the mask layer, and the dielectric layer 4 is deposited on the mask layer. The dielectric layer 4 covers the sacrificial layer 5'; after etching to form the cavity 7, the sacrificial layer 5' and the mask layer located on the piezoelectric layer 2 are removed. By forming a mask layer on the piezoelectric layer 2, the piezoelectric layer 2 is prevented from being etched when etching the cavity 7, thereby ensuring the integrity of the piezoelectric layer 2 and further improving the structural stability of the resonator.

[0087] In order to facilitate the subsequent formation of interdigital transducers, during the formation of the cavity 7, a first cavity 91 and a second cavity 92 also need to be formed, so that during the subsequent formation of the interdigital transducers, a first conductor 312 and a second conductor 322 are respectively formed in the first cavity 91 and the second cavity 92. The first cavity 91 and the second cavity 92 are parallel. The cavity 7 includes at least one first sub-cavity 71 and at least one second sub-cavity 72. The first sub-cavity 71 and the second sub-cavity 72 are parallel, and any first sub-cavity 71 and second sub-cavity 72 are adjacent. The first cavity 91 communicates with all the first sub-cavities 71 and is perpendicular to any first sub-cavity 71. The second cavity 92 communicates with all the second sub-cavities 72 and is perpendicular to any second sub-cavity 72.

[0088] Part of the bottom of the first cavity 91 extends to the sacrificial layer 5', part of the bottom extends to the upper surface of the piezoelectric layer 2, or all of the bottom of the first cavity 91 extends to the sacrificial layer 5', or all of the bottom of the first cavity 91 extends to the upper surface of the piezoelectric layer 2, so that the lower surface of the subsequently formed first conductor 312 is in contact with the upper surface of the piezoelectric layer 2; and / or, part of the bottom of the second cavity 92 extends to the sacrificial layer 5', part of the bottom extends to the upper surface of the piezoelectric layer 2, or all of the bottom of the second cavity 92 extends to the sacrificial layer 5', or all of the bottom of the second cavity 92 extends to the upper surface of the piezoelectric layer 2, so that the lower surface of the subsequently formed second conductor 322 is in contact with the upper surface of the piezoelectric layer 2. In this embodiment, the first cavity 91 and the second cavity 92 are formed when the cavity 7 is formed. It should be noted that the formation steps of the first cavity 91 and the second cavity 92 can refer to the formation steps of the cavity 7 above and will not be elaborated here. In other embodiments, the first cavity 91 and the second cavity 92 can be formed before or after the formation of the interdigital transducers.

[0089] Execute step S05 to remove the sacrificial layer and form a first cavity 5. Refer to Figure 7 , where the left figure is the cross-sectional structure schematic diagram corresponding to this step along Figure 1A A-A in Figure 1A and the right figure is the cross-sectional structure schematic diagram corresponding to this step along

[0090] In this embodiment, according to the material of the sacrificial layer, a corresponding removal method needs to be adopted. For example, when the sacrificial layer is α-C, the sacrificial layer is removed by plasma gas ablation. Another example is that when the sacrificial layer material is polyimide or photoresist, it is removed by ashing. Another example is that when the sacrificial layer material is low-temperature silicon dioxide, it reacts with hydrofluoric acid solvent to remove. It should be noted that the shape of the first cavity 5 formed after the removal of the sacrificial layer is the same as the shape of the sacrificial layer.

[0091] Execute step S06 to form a conductive material in the cavity 7 to form an interdigital transducer. Refer toFigure 8 , where the left figure is a schematic cross-sectional structure diagram corresponding to the step A-A in Figure 1A , and the right figure is a schematic cross-sectional structure diagram corresponding to the step B-B in Figure 1A .

[0092] When the interdigital transducer, the dielectric layer 4, and the piezoelectric layer 2 enclose the first cavity 5 to form a sealed first cavity 5, it is necessary to fill nitrogen, inert gas, or air into the first cavity 5 before forming the interdigital transducer.

[0093] In this embodiment, the interdigital transducer includes: a first group of interdigital transducers and a second group of interdigital transducers. Specifically, the first group of interdigital transducers includes at least one first conductive finger 311, the second group of interdigital transducers includes at least one second conductive finger 321, and the first conductive finger 311 and the second conductive finger 321 are parallel to each other. The method of forming the interdigital transducer includes: filling a conductive material into the cavity 7 to form a conductive material layer, and then planarizing the upper surface of the conductive material layer by a chemical mechanical polishing process (CMP) so that the upper surface of the conductive material layer is flush with the dielectric layer 4, thereby forming the interdigital transducer, where the first conductive finger 311 is formed in the first sub-cavity 71 and the second conductive finger 321 is formed in the second sub-cavity 72.

[0094] It should be noted that when the first cavity 91 and the second cavity 92 are formed synchronously with the cavity 7, or when the first cavity 91 and the second cavity 92 are formed before forming the interdigital transducer, during the process of forming the interdigital transducer, when filling the conductive material into the cavity 7, the conductive material is also filled into the first cavity 91 and the second cavity 92, so that when forming the interdigital transducer, the first conductor 312 and the second conductor 322 are also formed. The first conductor 312 is formed in the first cavity 91, and the second conductor 322 is formed in the second cavity 92. Since the first cavity 91 communicates with all the first sub-cavities 71 and the second cavity 92 communicates with all the second sub-cavities 72, the first conductor 312 is electrically connected to all the first conductive fingers 311, and the second conductor 322 is electrically connected to all the second conductive fingers 321.

[0095] The selection of the conductive material can refer to the materials of the first conductive finger 311 and the second conductive finger 321 in the above structural embodiment, which will not be elaborated here. The method of filling the conductive material can be deposition or electroplating such as magnetron sputtering and evaporation. The deposition method can be chemical vapor deposition or physical vapor deposition. During the electroplating process, it is necessary to form a seed layer on the region of the piezoelectric layer 2 opposite to the cavity before forming the sacrificial layer or after removing the sacrificial layer, so that after forming the cavity 7 and removing the sacrificial layer, the interdigital transducer 3 is formed on the seed layer, and the material of the seed layer can be formed by titanium (Ti).

[0096] After the interdigital transducer is formed, the interdigital transducer divides the first cavity 5 into a plurality of first sub-cavities, and adjacent first sub-cavities are isolated from each other or communicated with each other. For the specific situation, refer to the structural embodiments described above, and details are not described herein again.

[0097] For facilitating the input or output of electrical signals, a first conductive bump 61 and a second conductive bump 62 are further included. Refer to Figure 9 , where: the left figure is a schematic cross-sectional structure diagram corresponding to this step along Figure 1A A-A in Figure 1A and the right figure is a schematic cross-sectional structure diagram corresponding to this step along

[0098] In this embodiment, the first conductive bump 61 and the second conductive bump 62 can be formed synchronously with the first conductive interdigital fingers 311, the second conductive interdigital fingers 321, the first conductive interdigital fingers 311 and the second conductive interdigital fingers 321. Specifically: a bump material layer is formed, filled in the first cavity 91 and the second cavity 92 and covering part or all of the second dielectric layer 42; the surface of the bump material layer is kept flat by chemical mechanical polishing (CMP); the bump material layer is etched to remove the bump material layer in the area outside the first conductor 312 and its adjacent part of the second dielectric layer 42, and to remove the bump material layer in the area outside the second conductor 322 and its adjacent part of the second dielectric layer 42, so that the bump material layer in the first cavity 91 forms the first conductor 312, the bump material layer in the second cavity 92 forms the second conductor 322, the bump material layer on the first conductor 312 and its adjacent part of the second dielectric layer 322 forms the first conductive bump 61, the bump material layer on the second conductor 322 and its adjacent part of the second dielectric layer 322 forms the second conductive bump 62, the bump material layer in the first sub-cavity 71 forms the first conductive interdigital fingers 311, and the bump material layer in the second sub-cavity 72 forms the second conductive interdigital fingers 321.

[0099] The first conductive bump is located on the first conductor 312, and the second conductive bump 62 is located on the second conductor 322, so that the first conductive bump 61 is electrically connected to the first group of interdigital transducers, and the second conductive bump 62 is electrically connected to the second group of interdigital transducers, thereby inputting or outputting signals to the first group of interdigital transducers and the second group of interdigital transducers respectively through the first conductive bump 61 and the second conductive bump 62.

[0100] The first conductive bump 61 and the second conductive bump 62 are located in a region outside the first cavity 5. Specifically, the first conductive bump 61 is located on the first conductor 312 or part of the first conductive bump 61 is located on the first conductor 312 and part is located on the second dielectric layer 42 adjacent to the first conductor 312; and / or, the second conductive bump 62 is located on the second conductor 322 or part of the second conductive bump 62 is located on the second conductor 322 and part is located on the second dielectric layer 42 adjacent to the second conductor 322. The positional relationship of the first conductive bump 61 with respect to the first conductor 312, the first dielectric layer 41, and the second dielectric layer 42 and the positional relationship of the second conductive bump 62 with respect to the second conductor 322, the first dielectric layer 41, and the second dielectric layer 42 can be referred to those described in the previous structural embodiments. The materials of the first conductive bump 61 and the second conductive bump 62 can be referred to those described in the previous structural embodiments and will not be elaborated here.

[0101] In other embodiments, the first conductive bump 61 and the second conductive bump 62 may not be formed synchronously with the first conductive interdigital fingers 311, the second conductive interdigital fingers 321, the first conductive interdigital fingers 311 and the second conductive interdigital fingers 321. Specifically, after forming the first conductive interdigital fingers 311, the second conductive interdigital fingers 321, the first conductive interdigital fingers 311 and the second conductive interdigital fingers 321, a bump material layer is formed on the upper surface of the dielectric layer 4 and the interdigital transducer; the bump material layer is planarized by a chemical mechanical polishing process (CMP); the bump material layer is etched to respectively form the first conductive bump 61 at least partially located on the first conductor 312 and the second conductive bump 62 at least partially located on the second conductor 322. The first conductive bump 61 is electrically connected to the first group of interdigital transducers, and the second conductive bump 62 is electrically connected to the second group of interdigital transducers. The first conductive bump 61 and the second conductive bump 62 are located in a region outside the first cavity 5.

[0102] In this embodiment, the piezoelectric layer 2 is a thick piezoelectric wafer. After forming the interdigital transducer 3, the piezoelectric layer 2 needs to be thinned. Refer to Figure 10 , in which the left figure is the cross-sectional structure schematic diagram corresponding to this step along Figure 1A A - A in Figure 1ASchematic cross-sectional structure diagram corresponding to the step of B-B in the figure. Specifically, the side of the piezoelectric layer 2 away from the first cavity 5 is thinned; a substrate 1 is provided and bonded to the thinned side of the piezoelectric layer 2. So that the piezoelectric layer 2 is thinner, thereby ensuring that the piezoelectric layer 2 has a better piezoelectric effect. In other embodiments, the step of thinning the piezoelectric layer 2 may be performed before forming the sacrificial layer 7, and the specific steps may refer to the foregoing and will not be elaborated here. In other embodiments, when the substrate 1 is a double-layer structure, that is, the substrate 1 includes a support layer 11 and a base 12, the support layer 11 and the substrate 12 are sequentially bonded to the thinned side of the piezoelectric layer 2. The bonding method may refer to that described in the foregoing structural embodiments and will not be elaborated here.

[0103] In summary, the manufacturing method of the thin film bulk acoustic wave resonator provided by the present invention forms a first cavity by forming a sacrificial layer on the piezoelectric layer, so as to facilitate the formation of a thin first cavity, thereby effectively releasing the sacrificial layer and avoiding the excessive outward expansion of the width of the subsequent formed interdigital electrodes; the formed first cavity can suspend the dielectric layer between the gaps of the interdigital transducer, so as to reflect the acoustic wave propagating along the surface of the piezoelectric layer back, thereby reducing the acoustic wave energy consumption. In addition, it can make the boundary of the interdigital transducer adjacent to the piezoelectric layer contact the gas in the first cavity, so as to effectively eliminate the boundary clutter; by first forming a cavity in the dielectric layer and then forming an interdigital transducer in the cavity, the etching of the piezoelectric layer during the formation of the traditional interdigital transducer is avoided, ensuring the flatness of the piezoelectric layer, and the formed cavity is used to limit the distance between the interdigital transducers to solve the problem that the traditional etching process cannot achieve a small distance.

[0104] Furthermore, the sacrificial layer is made of α-C material, which is convenient for forming a thin first cavity with a small height subsequently.

[0105] Furthermore, when the thickness of the piezoelectric layer is thin, a substrate is bonded under the piezoelectric layer to support the piezoelectric layer and avoid the piezoelectric layer being deformed under pressure during the subsequent formation of the sacrificial layer, dielectric layer, and interdigital transducer, thereby ensuring the structural strength of the piezoelectric layer; when the thickness of the piezoelectric layer is thick, it can avoid the piezoelectric layer being deformed under pressure during the subsequent formation of the sacrificial layer, dielectric layer, and interdigital transducer. After forming the interdigital transducer, the piezoelectric layer is thinned to ensure that the piezoelectric layer has good piezoelectric characteristics, thereby improving the overall characteristics of the resonator.

[0106] It should be noted that each embodiment in this specification is described in a related manner, and the same or similar parts between each embodiment can be referred to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the structural embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiments.

[0107] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention in any way. Any changes and modifications made by those of ordinary skill in the art of the present invention based on the above disclosure fall within the scope of protection of the claims.

Claims

1. A surface acoustic wave resonator, characterized in that, Comprising: A substrate and a piezoelectric layer disposed on the substrate; Interdigital transducers disposed on the upper surface of the piezoelectric layer; A first dielectric layer is provided between the gaps of the interdigital transducers, and a first cavity is provided between the lower surface of at least a part of the first dielectric layer and the upper surface of the piezoelectric layer, and the first cavity suspends the first dielectric layer between the gaps of the interdigital transducers.

2. The surface acoustic wave resonator according to claim 1, wherein, The interdigital transducers divide the first cavity into a plurality of sub-first cavities, and adjacent sub-first cavities are isolated from each other or communicate with each other.

3. The surface acoustic wave resonator according to claim 1, wherein, A first cavity exists between the upper surface of the piezoelectric layer and the first dielectric layer between all the gaps.

4. The surface acoustic wave resonator according to claim 1, wherein, A second dielectric layer is provided on the outer periphery of the interdigital transducers and is deposited on the substrate and connected to the first dielectric layer.

5. The surface acoustic wave resonator according to claim 1, characterized in that The first dielectric layer and the second dielectric layer are of an integral structure and have the same material.

6. The surface acoustic wave resonator according to claim 1, wherein The first cavity is a sealed first cavity or the first cavity communicates with the outside.

7. The surface acoustic wave resonator according to claim 1, wherein The first cavity is a sealed first cavity, and the first cavity is filled with nitrogen, inert gas or air.

8. The surface acoustic wave resonator according to claim 1, characterized in that, The height of the first cavity is 0.05um to 1um.

9. The surface acoustic wave resonator according to claim 1, wherein, The interdigital transducers include: a first group of interdigital transducers and a second group of interdigital transducers. The first group of interdigital transducers includes at least one first conductive finger, and the second group of interdigital transducers includes at least one second conductive finger. The first conductive finger and the second conductive finger are parallel to each other; Further comprising: a first conductive bump and a second conductive bump. The first conductive bump is electrically connected to the first group of interdigital transducers, and the second conductive bump is electrically connected to the second group of interdigital transducers. The first conductive bump and the second conductive bump are located outside the first cavity.

10. The surface acoustic wave resonator according to claim 1, wherein The material of the first dielectric layer includes at least one of silicon carbide, silicon nitride, sapphire, silicon dioxide, aluminum nitride.

11. The surface acoustic wave resonator according to claim 1, wherein The material of the interdigital transducers includes one or more of gold, silver, tungsten, platinum, aluminum, copper.

12. The surface acoustic wave resonator according to claim 1, wherein, A second cavity is provided in the substrate, and the interdigital transducer is located above the area surrounded by the second cavity.

13. The surface acoustic wave resonator according to claim 1, characterized in that, A Bragg acoustic wave reflection layer is provided in the substrate, and the interdigital transducer is located above the area surrounded by the Bragg acoustic wave reflection layer.

14. A manufacturing method of a surface acoustic wave resonator, characterized in that, Comprising: Providing a piezoelectric layer; Forming a sacrificial layer to cover a first region of the piezoelectric layer; Forming a dielectric layer to cover the piezoelectric layer and the sacrificial layer; Forming a plurality of longitudinally penetrating cavities in the dielectric layer above the sacrificial layer, and at least a part of the bottom of the cavities extends to the sacrificial layer; Removing the sacrificial layer to form a first cavity; Forming a conductive material in the cavities to form interdigital transducers.

15. The manufacturing method of the surface acoustic wave resonator according to claim 14, characterized in that, The sacrificial layer is formed on the piezoelectric layer by chemical vapor deposition process under the conditions of 200 degrees to 400 degrees, normal pressure or low pressure.

16. The manufacturing method of the surface acoustic wave resonator according to claim 14, wherein, The thickness of the sacrificial layer is 0.05um to 1um.

17. The manufacturing method of the surface acoustic wave resonator according to claim 14, characterized in that, The sacrificial layer is removed by the method of plasma gas ablation.

18. The manufacturing method of the surface acoustic wave resonator according to claim 14, characterized in that, A part of the boundary of the sacrificial layer coincides with the boundary of the dielectric layer or extends beyond the boundary of the dielectric layer and communicates with the outside. After removing the sacrificial layer, the first cavity communicates with the outside; Alternatively, the boundary of the sacrificial layer is located inside the boundary of the dielectric layer. After removing the sacrificial layer, the first cavity is a sealed first cavity.

19. The method for manufacturing a surface acoustic wave resonator according to claim 14, after forming the interdigital transducer, the interdigital transducer divides the first cavity into a plurality of first sub-cavities. When the boundary of the cavity extends beyond the boundary of the first cavity, adjacent first sub-cavities are isolated from each other. When the boundary of the cavity is located within the boundary of the first cavity, adjacent first sub-cavities communicate with each other.

20. The manufacturing method of the surface acoustic wave resonator according to claim 14, characterized in that, The interdigital transducer, the dielectric layer, and the piezoelectric layer enclose the first cavity to form a sealed first cavity. Before forming the interdigital transducer, it further includes filling nitrogen or inert gas into the first cavity.

21. The manufacturing method of the surface acoustic wave resonator according to claim 14, characterized in that, The thickness of the piezoelectric layer is less than 20 microns or the thickness of the piezoelectric layer is greater than 0.3 microns. When the thickness of the piezoelectric layer is greater than 0.3 microns, the manufacturing method further includes: Thinning the side of the piezoelectric layer away from the first cavity; Providing a substrate and bonding it to the thinned side of the piezoelectric layer.

22. The manufacturing method of the surface acoustic wave resonator according to claim 14, characterized in that, At least part of the bottom of the cavity extending to the sacrificial layer includes: part of the bottom of the cavity extending to the sacrificial layer and part of the bottom extending to the upper surface of the piezoelectric layer, or all of the bottom of the cavity extending to the sacrificial layer; The bottom of the cavity extending to the sacrificial layer includes: The bottom of the cavity extends to the upper surface of the sacrificial layer or penetrates the sacrificial layer to extend to the upper surface of the piezoelectric layer or penetrates part of the sacrificial layer to extend into the sacrificial layer.

23. The manufacturing method of the surface acoustic wave resonator according to claim 14, characterized in that, The interdigital transducer includes: a first group of interdigital transducers and a second group of interdigital transducers. The first group of interdigital transducers includes at least one first conductive finger, and the second group of interdigital transducers includes at least one second conductive finger. The first conductive finger and the second conductive finger are parallel to each other. The method for forming the interdigital transducer includes: Filling a conductive material into the cavity to form the interdigital transducer, where the first conductive finger and the second conductive finger are respectively formed in adjacent cavities.

24. The manufacturing method of the surface acoustic wave resonator according to claim 23, wherein, The method further includes: Forming a first conductive bump and a second conductive bump. The first conductive bump is electrically connected to the first group of interdigital transducers, and the second conductive bump is electrically connected to the second group of interdigital transducers. The first conductive bump and the second conductive bump are located outside the boundary of the region enclosed by the first cavity.

25. The manufacturing method of the surface acoustic wave resonator according to claim 14, characterized in that, The material of the dielectric layer includes silicon carbide or silicon nitride.

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