A temperature-compensated thin-film bulk acoustic resonator and its preparation method and filter

Abstract

The present invention provides a temperature-compensated thin-film bulk acoustic wave resonator, a preparation method thereof, and a filter, and relates to the technical field of bulk acoustic wave resonators. The preparation method comprises the following steps: obtaining a first substrate of a single crystal and depositing a single crystal aluminum nitride piezoelectric layer on the first substrate; after depositing a bottom electrode on the piezoelectric layer, depositing a polycrystalline silicon dioxide temperature compensation layer on the bottom electrode to obtain a first semi-finished product; obtaining a second substrate and opening a groove; bonding the temperature compensation layer of the first semi-finished product to the second substrate and making the temperature compensation layer cover the groove to form a cavity to obtain a second semi-finished product; removing the first substrate on the second semi-finished product and depositing a top electrode to obtain a finished product. The preparation method of the present invention avoids growing a single crystal aluminum nitride piezoelectric layer on the polycrystalline silicon dioxide temperature compensation layer while avoiding damage to the device during the release process, thereby achieving the effect of improving the crystal quality of the piezoelectric layer and improving the filter performance.

Description

Technical Field

[0001] The present invention relates to the technical field of bulk acoustic wave resonators, and in particular to a temperature-compensated thin film bulk acoustic wave resonator and a preparation method and a filter thereof. Background Art

[0002] Reference Figure 2 A temperature-compensated thin film bulk acoustic wave resonator is now disclosed, comprising a second substrate 100, a bottom electrode 300, a second temperature-compensating layer 700 of polycrystalline silicon dioxide, a piezoelectric layer 400 of single-crystalline aluminum nitride and a top electrode 500 stacked in sequence, wherein a cavity 600 is also provided between the second substrate 100 and the bottom electrode 300. During the preparation process of the resonator, each layer is deposited in sequence, and finally a sacrificial layer between the second substrate 100 and the bottom electrode 300 is released through a release process to form the cavity 600.

[0003] However, this preparation method has the following defects:

[0004] 1. The release process will cause the bottom electrode to be corroded, resulting in damage to the device;

[0005] 2. The piezoelectric layer is grown on the basis of the temperature compensation layer. Due to the lattice mismatch between the piezoelectric layer and the temperature compensation layer, the crystal quality of the grown piezoelectric layer is reduced, thereby reducing the performance of the filter manufactured subsequently.

[0006] There is currently no effective technical solution to the above problems. Summary of the invention

[0007] The object of the present invention is to provide a temperature-compensated thin film bulk acoustic wave resonator, a preparation method thereof and a filter, which can avoid damaging the device during the release process while avoiding growing a piezoelectric layer of single-crystal aluminum nitride on a temperature-compensated layer of polycrystalline silicon dioxide, thereby achieving the effect of improving the crystal quality of the piezoelectric layer and improving the performance of the filter.

[0008] In a first aspect, the present invention provides a preparation method for preparing a temperature-compensated thin film bulk acoustic resonator, comprising the following steps:

[0009] S1. Obtaining a first substrate made of a single crystal material and depositing a piezoelectric layer on the first substrate using single crystal aluminum nitride as the material;

[0010] S2. After depositing a bottom electrode on the piezoelectric layer, a first temperature compensation layer is deposited on the bottom electrode using polycrystalline silicon dioxide as a material to obtain a first semi-finished product;

[0011] S3. Obtain a second substrate and open a groove on the second substrate;

[0012] S4. Bonding the first temperature compensation layer of the first semi-finished product to the second substrate and allowing the first temperature compensation layer to cover the groove to form a cavity, thereby obtaining a second semi-finished product;

[0013] S5. After removing the first substrate on the second semi-finished product, a top electrode is deposited on the piezoelectric layer to obtain a finished product.

[0014] The preparation method provided by the present invention replaces the traditional layer-by-layer growth process with a flip-chip bonding process, first deposits a piezoelectric layer of single-crystal aluminum nitride, and then deposits a first temperature compensation layer of polycrystalline silicon dioxide based on the piezoelectric layer, thereby avoiding damage to the device by the release process and improving the crystal quality of the piezoelectric layer, thereby improving the filter performance.

[0015] Furthermore, the specific steps in step S2 include:

[0016] S21. Depositing a second temperature compensation layer on the piezoelectric layer using polycrystalline silicon dioxide as a material; the thickness of the second temperature compensation layer is less than the thickness of the first temperature compensation layer;

[0017] S22. Depositing the bottom electrode on the second temperature compensating layer.

[0018] The solution of using a thick first temperature compensation layer and a thin second temperature compensation layer to cooperate with each other is adopted to take into account and balance the two aspects of temperature compensation and effective electromechanical coupling coefficient, so as to further improve the overall performance of the device.

[0019] Furthermore, the specific steps in step S2 include:

[0020] S23. Determine the deposition thickness of the first temperature compensation layer according to the wavelength corresponding to the preset frequency.

[0021] Furthermore, the second substrate is made of silicon material; the specific steps in step S4 include:

[0022] S41. Bonding the first temperature compensation layer of the first semi-finished product to the second substrate in a non-metallic bonding manner.

[0023] Compared with metal bonding, non-metal bonding requires a lower heating temperature, which not only reduces the bonding difficulty, but also reduces the damage to the device caused by high temperature.

[0024] Furthermore, the specific steps in step S5 include:

[0025] S51. After depositing the top electrode on the piezoelectric layer, deposit a protective layer on the top electrode.

[0026] The protective layer can prevent the layer structure from being corroded by the external environment, which is beneficial to extending the service life of the device.

[0027] In the second aspect, the present invention provides a temperature-compensated thin film bulk acoustic wave resonator prepared based on the above-mentioned preparation method, comprising a second substrate, a first temperature compensating layer, a bottom electrode, a piezoelectric layer and a top electrode stacked in sequence, a cavity is arranged between the second substrate and the first temperature compensating layer; the first temperature compensating layer is made of polycrystalline silicon dioxide material; the piezoelectric layer is made of single crystal aluminum nitride material.

[0028] The first temperature compensation layer is located outside the sandwich structure and is used to compensate the temperature of the piezoelectric layer to ensure the performance of the device and avoid the problem of a serious decrease in the effective electromechanical coupling coefficient of the filter bandwidth performance.

[0029] Furthermore, it also includes a second temperature compensation layer located between the bottom electrode and the piezoelectric layer, and the thickness of the second temperature compensation layer is smaller than the thickness of the first temperature compensation layer.

[0030] Furthermore, the second substrate is made of silicon material.

[0031] In a third aspect, the present invention provides a filter, comprising the temperature compensated thin film bulk acoustic wave resonator described above.

[0032] Further, it includes an input end, an output end, at least two series resonators and at least two parallel resonators;

[0033] Wherein, all the series resonators and all the parallel resonators are the temperature compensated thin film bulk acoustic wave resonators;

[0034] The input end, all the series resonators and the output end are connected in series in sequence; one end of all the parallel resonators is grounded; any two adjacent series resonators are connected to an ungrounded end of a parallel resonator; the series resonator connected to the output end and the output end are connected to an ungrounded end of a parallel resonator.

[0035] As can be seen from the above, the preparation method provided by the present invention divides the device into two parts for preparation, in which a piezoelectric layer of single-crystal aluminum nitride is first deposited to ensure that the piezoelectric layer has a higher crystal quality, and then a first temperature compensation layer of polycrystalline silicon dioxide is deposited to avoid the lattice structure of the first temperature compensation layer affecting the crystal quality of the piezoelectric layer; and a groove is opened in the other part, and finally the two parts are connected by flip-chip bonding, which not only eliminates the release process and avoids damage to the device caused by the release process, but also improves the crystal quality of the piezoelectric layer and avoids affecting the performance of the subsequently manufactured filter.

[0036] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or be understood by implementing the embodiments of the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A flow chart of a preparation method provided in an embodiment of the present invention.

[0038] Figure 2 The figure is a schematic diagram of the structure of an existing temperature-compensated thin film bulk acoustic resonator.

[0039] Figure 3 A schematic structural diagram of a first temperature-compensated thin film bulk acoustic resonator provided in an embodiment of the present invention.

[0040] Figure 4 A schematic diagram of the preparation process of a first temperature-compensated thin film bulk acoustic resonator provided in an embodiment of the present invention.

[0041] Figure 5 FIG. 4 is an impedance curve diagram of a filter made of the first temperature-compensated thin film bulk acoustic resonator in an embodiment of the present invention.

[0042] Figure 6 This is a Q value test curve diagram of the filter made of the first temperature compensated thin film bulk acoustic resonator in an embodiment of the present invention.

[0043] Figure 7 A schematic structural diagram of a second temperature-compensated thin film bulk acoustic resonator provided in an embodiment of the present invention.

[0044] Figure 8 A schematic diagram of the preparation process of a second temperature-compensated thin film bulk acoustic resonator provided in an embodiment of the present invention.

[0045] Fig. 9 FIG. 4 is an impedance curve diagram of a filter made of the second temperature-compensated thin film bulk acoustic resonator in an embodiment of the present invention.

[0046] Fig.10 This is a Q value test curve diagram of the filter made of the second temperature compensated thin film bulk acoustic resonator in an embodiment of the present invention.

[0047] Fig.11 A schematic diagram of the structure of a filter provided by an embodiment of the present invention.

[0048] Description of labels:

[0049] 100, second substrate; 200, first temperature compensation layer; 300, bottom electrode; 400, piezoelectric layer; 500, top electrode; 600, cavity; 700, second temperature compensation layer; 810, input end; 820, output end; 831, first series resonator; 832, second series resonator; 833, third series resonator; 834, fourth series resonator; 841, first parallel resonator; 842, second parallel resonator; 843, third parallel resonator; 844, fourth parallel resonator; 900, first substrate; 1000, protective layer. DETAILED DESCRIPTION

[0050] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0051] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0052] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0053] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0054] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0055] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present invention.

[0056] It should be noted that similar numbers and letters represent similar items in the following figures, so once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. At the same time, in the description of the present invention, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0057] Reference Figure 1 , Attachment Figure 4 and attached Figure 8 The present invention provides a preparation method for preparing a temperature-compensated thin film bulk acoustic resonator, comprising the following steps:

[0058] S1. Obtaining a first substrate made of a single crystal material and depositing a piezoelectric layer on the first substrate using single crystal aluminum nitride as the material;

[0059] S2. After depositing a bottom electrode on the piezoelectric layer, a first temperature compensation layer is deposited on the bottom electrode using polycrystalline silicon dioxide as a material to obtain a first semi-finished product;

[0060] S3. Obtain a second substrate and open a groove on the second substrate;

[0061] S4. Bonding the first temperature compensation layer of the first semi-finished product to the second substrate and allowing the first temperature compensation layer to cover the groove to form a cavity to obtain a second semi-finished product;

[0062] S5. After removing the first substrate on the second semi-finished product, a top electrode is deposited on the piezoelectric layer to obtain a finished product.

[0063] Most of the existing temperature-compensated thin-film bulk acoustic wave resonators are generally manufactured in a bottom-up order during the preparation process. According to the order of each layer, the single-crystalline aluminum nitride piezoelectric layer is often grown on the basis of the polycrystalline silicon dioxide temperature compensation layer after the temperature compensation layer is completed. However, due to the lattice incompatibility between single-crystalline aluminum nitride and polycrystalline silicon dioxide, the piezoelectric layer cannot grow a high-quality crystal structure.

[0064] Specifically, the reasons for the low-quality crystal structure are:

[0065] 1. Lattice mismatch will bring stress to the piezoelectric layer, resulting in defects such as dislocations and interface traps in the crystal structure of the piezoelectric layer;

[0066] 2. Since the grain boundaries of polycrystalline materials are uneven and there are grains with different orientations, the surface of polycrystalline materials is relatively rough, so that the crystal structure of the piezoelectric layer also presents uneven defects;

[0067] 3. The grain orientations of polycrystalline materials are different, so the crystal structure of the piezoelectric layer also has many different crystal orientations.

[0068] In summary, the crystal structure of the piezoelectric layer grown on the polycrystalline material often has defects such as those mentioned above, so that the piezoelectric layer has a high defect density. These defects will affect the mobility of electrons and the carrier lifetime of the material, thereby affecting the overall performance of the device.

[0069] It should be noted that the adverse effects of the polycrystalline silicon dioxide temperature compensating layer on the upper single crystal aluminum nitride piezoelectric layer cannot be curbed by setting an additional layer structure between the temperature compensating layer and the piezoelectric layer. For example, although a bottom electrode is set between the temperature compensating layer and the piezoelectric layer to isolate the temperature compensating layer from the piezoelectric layer, the polycrystalline structure of the temperature compensating layer will still affect the growth of the single crystal structure of the piezoelectric layer. Therefore, as long as the single crystal piezoelectric layer is grown based on the polycrystalline temperature compensating layer, the above defects will occur.

[0070] In this regard, different from the existing preparation method of manufacturing each layer sequentially, this embodiment first manufactures a single crystal piezoelectric layer 400 on a single crystal first substrate 900, thereby preventing the growth of the piezoelectric layer from being affected by the polycrystalline structure, and then grows a polycrystalline first temperature compensation layer 200 based on the single crystal piezoelectric layer. Thereafter, a flip-chip bonding process is used to bond the first semi-finished product to the second substrate 100 to obtain a finished product.

[0071] The preparation method of this embodiment has the following advantages:

[0072] 1. It avoids growing a single crystal piezoelectric layer based on a polycrystalline temperature compensation layer. The first substrate of the single crystal provides a uniform and defect-free lattice structure for the growth of the piezoelectric layer, which is conducive to forming a high-quality, low-defect density piezoelectric layer, thereby improving the quality of the piezoelectric layer crystal, and further improving the overall performance of the device;

[0073] 2. The structure of the BAW resonator includes a cavity for forming an acoustic wave reflection interface. In the existing preparation method, the cavity is formed by removing the sacrificial layer in the cavity through a release process after the various layers of the structure are completed. Without protection, the release process of the sacrificial layer often corrodes its upper structure (for example, according to the existing preparation method, each layer is manufactured in sequence, and the cavity is located between the substrate and the temperature compensation layer. When the sacrificial layer in the cavity is released, the temperature compensation layer will be corroded), resulting in failure of the entire device. The use of the flip-chip bonding process can cancel the release process, thereby avoiding corrosion of the layer structure, which is beneficial to improving the yield of the device. At the same time, there is no need to protect the layer structure due to the release of the sacrificial layer, which saves the process flow and is beneficial to improving production efficiency.

[0074] 3. By adopting the inverted bonding process, when preparing the first semi-finished product, it is easier to comply with the preparation requirements of growing a polycrystalline temperature compensation layer on the basis of a single crystal piezoelectric layer while still being able to produce each layer in sequence without increasing the difficulty of preparation, which is beneficial to avoiding a large increase in manufacturing costs.

[0075] It should also be noted that in order to further ensure that a single-crystal aluminum nitride piezoelectric layer with higher crystal quality is obtained, in addition to growing the piezoelectric layer on the single-crystal first substrate, the piezoelectric layer should be produced by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE).

[0076] In addition, the grooves may be formed on the second substrate by, but not limited to, photolithography, nanoimprinting, dry etching or wet etching.

[0077] In addition, the first substrate may be removed by a laser lift-off method, and then the top electrode may be deposited after improving the surface flatness by chemical-mechanical polishing (CMP).

[0078] Reference Figure 8 In some embodiments, the specific steps in step S2 include:

[0079] S21. A second temperature compensation layer is deposited on the piezoelectric layer using polycrystalline silicon dioxide as the material; the thickness of the second temperature compensation layer is less than the thickness of the first temperature compensation layer;

[0080] S22. Deposit a bottom electrode on the second temperature compensation layer.

[0081] In this embodiment, the second temperature compensating layer is also deposited on the piezoelectric layer of the single crystal as the basis. Different from the first temperature compensating layer, in the finished product, the first temperature compensating layer is located outside the sandwich structure (bottom electrode-piezoelectric layer-top electrode). On the one hand, it plays a role in compensating the temperature of the piezoelectric layer, thereby improving the device performance. On the other hand, it does not constitute a capacitive voltage divider in the sandwich structure, thereby avoiding reducing the effective electromechanical coupling coefficient of the filter. The second temperature compensating layer is located in the sandwich structure. Since the second temperature compensating layer is adjacent to the piezoelectric layer, the temperature compensation effect on the piezoelectric layer is better than that of the first temperature compensating layer. However, compared with the first temperature compensating layer, the second temperature compensating layer constitutes a capacitive voltage divider in the sandwich structure. In order to reduce the influence of the second temperature compensating layer on the effective electromechanical coupling coefficient of the filter, the thickness of the second temperature compensating layer is designed to be less than that of the first temperature compensating layer.

[0082] Compared with the existing BAW resonator that only sets a temperature compensation layer outside the sandwich structure, the BAW resonator of this embodiment has a better temperature compensation effect; compared with the existing BAW resonator that only sets a thicker temperature compensation layer inside the sandwich structure, the filter made of the BAW resonator of this embodiment has a higher effective electromechanical coupling coefficient. This embodiment adopts a solution of cooperating a thick first temperature compensation layer and a thin second temperature compensation layer to take into account and balance the two aspects of temperature compensation and effective electromechanical coupling coefficient, thereby achieving the effect of further improving the overall performance of the device.

[0083] In some embodiments, the specific steps in step S2 include:

[0084] S23. Determine the deposition thickness of the first temperature compensation layer according to the wavelength corresponding to the preset frequency.

[0085] Specifically, the filter frequency to be designed is used as the preset frequency, and the deposition thickness of the first temperature compensation layer is twice the wavelength of the preset frequency. For example, if the preset frequency is 2.5 GHz, the deposition thickness of the first temperature compensation layer is 1300 nm.

[0086] In some embodiments, the second substrate is made of silicon material; the specific steps in step S4 include:

[0087] S41. Bond the first temperature compensation layer of the first semi-finished product to the second substrate in a non-metallic bonding manner.

[0088] In this embodiment, based on the flip-chip bonding process, in accordance with the preparation requirements of growing a polycrystalline temperature compensating layer on the basis of a single crystal piezoelectric layer, the polycrystalline temperature compensating layer is used as the top layer of the first semi-finished product, and is bonded to the second substrate by utilizing the property of non-metallic bonding between silicon and silicon dioxide. Compared with metal bonding, the heating temperature required for non-metallic bonding is lower, which not only reduces the bonding difficulty, but also reduces the damage to the device caused by high temperature.

[0089] In some embodiments, the specific steps in step S5 include:

[0090] S51. After depositing a top electrode on the piezoelectric layer, deposit a protective layer on the top electrode.

[0091] The protective layer 1000 can prevent the layer structure from being corroded by the external environment, which is beneficial to prolonging the service life of the device.

[0092] Reference Figure 3 The present invention provides a temperature-compensated thin film bulk acoustic wave resonator prepared by the preparation method in the above embodiment, comprising a second substrate 100, a first temperature compensating layer 200, a bottom electrode 300, a piezoelectric layer 400 and a top electrode 500 stacked in sequence, a cavity 600 is arranged between the second substrate 100 and the first temperature compensating layer 200; the first temperature compensating layer 200 is made of polycrystalline silicon dioxide material; the piezoelectric layer 400 is made of single crystal aluminum nitride material.

[0093] In this embodiment, the first temperature compensation layer 200 is located outside the sandwich structure to compensate for the temperature of the piezoelectric layer 400 to ensure the device performance. It can avoid forming a capacitive voltage divider in the sandwich structure, thereby preventing the voltage of the piezoelectric layer 400 from being reduced, thereby avoiding the problem of a serious decrease in the effective electromechanical coupling coefficient of the filter bandwidth performance.

[0094] Reference Figure 5Experiments have shown that, compared with existing filters made of bulk acoustic wave resonators without a temperature compensation layer, the resonant frequency temperature coefficient (i.e., TCF coefficient) of the existing filters is generally about -30ppm / ℃, while the TCF coefficient of the filter in this embodiment is about -9.5ppm / ℃. It can be seen that the temperature stability of the filter in this embodiment is better.

[0095] At the same time, refer to the attached Figure 6 Compared with the existing filter made of traditional temperature-compensated thin film bulk acoustic resonator, the quality factor (Q value) of the existing filter is 1500 at a frequency of about 2.4 GHz, and the effective electromechanical coupling coefficient (i.e. ) is 3%-4%, and the Q value of the filter made of the bulk acoustic wave resonator of this embodiment is 3406 when the frequency is about 2.4GHz. It is 5.99%, which shows that the two performance parameters of the filter in this embodiment are much higher than those of the existing filter.

[0096] In certain embodiments, referring to Figure 7 The temperature-compensated FBAW resonator further includes a second temperature compensating layer 700 located between the bottom electrode 300 and the piezoelectric layer 400 . The thickness of the second temperature compensating layer 700 is smaller than that of the first temperature compensating layer 200 .

[0097] In this embodiment, a second temperature compensating layer 700 is provided in the sandwich structure to cooperate with the first temperature compensating layer 200 to further improve the temperature stability of the device. Although the second temperature compensating layer 700 forms a capacitive voltage divider in the sandwich structure, the influence of the second temperature compensating layer 700 on the effective electromechanical coupling coefficient can be reduced by reducing the thickness of the second temperature compensating layer 700. For example, the thickness of the first temperature compensating layer 200 is 1300 nm, and the thickness of the second temperature compensating layer 700 is 20 nm.

[0098] Reference Fig. 9 and attached Fig.10 Experiments have shown that the first temperature compensation layer 200 and the second temperature compensation layer 700 cooperate with each other so that the filter of this embodiment has a TCF coefficient of +0.2ppm / ℃ and a Q value of 3022 when the frequency is about 2.4GHz. It is 5.99%, which shows that the performance of the filter in this embodiment is not seriously reduced compared with the filter in the previous embodiment, and is still greatly improved compared with the existing filter.

[0099] In some embodiments, the second substrate 100 is made of materials such as silicon, germanium, sapphire, quartz, silicon carbide, or organic polymer.

[0100] In some preferred embodiments, the second substrate 100 is made of silicon material. Silicon and silicon dioxide can be bonded non-metallicly, which makes it easier to bond the first semi-finished product to the second substrate 100 .

[0101] Reference Fig.11 The present invention provides a filter, comprising the temperature-compensated thin film bulk acoustic resonator in the above-mentioned embodiment.

[0102] In certain embodiments, referring to Fig.11 , the filter includes an input terminal 810, an output terminal 820, at least two series resonators and at least two parallel resonators;

[0103] Among them, the input end 810, all series resonators and the output end 820 are connected in series in sequence; one end of all parallel resonators is grounded; any two adjacent series resonators are connected to the ungrounded end of a parallel resonator; the series resonator connected to the output end 820 and the output end 820 are connected to the ungrounded end of a parallel resonator.

[0104] For details, please refer to the attached Fig.11 , including four series resonators, namely: a first series resonator 831, a second series resonator 832, a third series resonator 833 and a fourth series resonator 834, and including four parallel resonators, namely: a first parallel resonator 841, a second parallel resonator 842, a third parallel resonator 843 and a fourth parallel resonator 844;

[0105] Among them, the first series resonator 831, the second series resonator 832, the third series resonator 833, the fourth series resonator 834, the first parallel resonator 841, the second parallel resonator 842, the third parallel resonator 843 and the fourth parallel resonator 844 are all temperature compensated thin film bulk acoustic resonators of the above embodiment;

[0106] The first series resonator 831, the second series resonator 832, the third series resonator 833 and the fourth series resonator 834 are connected in series in sequence; the first series resonator 831 is connected to the input end 810; the fourth series resonator 834 is connected to the output end 820;

[0107] One end of the first parallel resonator 841 is connected between the first series resonator 831 and the second series resonator 832 and the other end is grounded;

[0108] One end of the second parallel resonator 842 is connected between the second series resonator 832 and the third series resonator 833 and the other end is grounded;

[0109] One end of the third parallel resonator 843 is connected between the third series resonator 833 and the fourth series resonator 834 and the other end is grounded;

[0110] One end of the fourth parallel resonator 844 is connected between the fourth series resonator 834 and the output terminal 820 and the other end is grounded.

[0111] In this document, relational terms such as first and second, etc. are used merely to distinguish one entity or operation from another entity or operation, but do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0112] Descriptions with reference to the terms "one embodiment", "certain embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" are intended to mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0113] The above description is only an embodiment of the present invention and is not intended to limit the protection scope of the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a temperature-compensated thin film bulk acoustic resonator, characterized in that: The following steps are involved: S1. Obtaining a first substrate made of a single crystal material and depositing a piezoelectric layer on the first substrate using single crystal aluminum nitride as the material; S2. After depositing a bottom electrode on the piezoelectric layer, a first temperature compensation layer is deposited on the bottom electrode using polycrystalline silicon dioxide as a material to obtain a first semi-finished product; S3. Obtain a second substrate and open a groove on the second substrate; S4. Bonding the first temperature compensation layer of the first semi-finished product to the second substrate and allowing the first temperature compensation layer to cover the groove to form a cavity, thereby obtaining a second semi-finished product; S5. After removing the first substrate on the second semi-finished product, a top electrode is deposited on the piezoelectric layer to obtain a finished product.

2. The preparation method according to claim 1, characterized in that: The specific steps in step S2 include: S21. Depositing a second temperature compensation layer on the piezoelectric layer using polycrystalline silicon dioxide as a material; the thickness of the second temperature compensation layer is less than the thickness of the first temperature compensation layer; S22. Depositing the bottom electrode on the second temperature compensating layer.

3. The preparation method according to claim 1, characterized in that: The specific steps in step S2 include: S23. Determine the deposition thickness of the first temperature compensation layer according to the wavelength corresponding to the preset frequency.

4. The preparation method according to claim 1, characterized in that: The second substrate is made of silicon material; the specific steps in step S4 include: S41. Bonding the first temperature compensation layer of the first semi-finished product to the second substrate in a non-metallic bonding manner.

5. The preparation method according to claim 1, characterized in that: The specific steps in step S5 include: S51. After depositing the top electrode on the piezoelectric layer, deposit a protective layer on the top electrode.

6. A temperature-compensated thin film bulk acoustic resonator prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The invention comprises a second substrate (100), a first temperature compensation layer (200), a bottom electrode (300), a piezoelectric layer (400) and a top electrode (500) which are stacked in sequence, wherein a cavity (600) is provided between the second substrate (100) and the first temperature compensation layer (200); the first temperature compensation layer (200) is made of polycrystalline silicon dioxide material; and the piezoelectric layer (400) is made of single crystal aluminum nitride material.

7. The temperature-compensated thin film bulk acoustic resonator according to claim 6, characterized in that: It also includes a second temperature compensation layer (700) located between the bottom electrode (300) and the piezoelectric layer (400), wherein the thickness of the second temperature compensation layer (700) is smaller than the thickness of the first temperature compensation layer (200).

8. The temperature-compensated thin film bulk acoustic resonator according to claim 6, characterized in that: The second substrate (100) is made of silicon material.

9. A filter, characterized in that: It comprises the temperature compensated thin film bulk acoustic resonator as claimed in any one of claims 6 to 8.

10. The filter according to claim 9, characterized in that comprising an input end (810), an output end (820), at least two series resonators and at least two parallel resonators; Wherein, all the series resonators and all the parallel resonators are the temperature compensated thin film bulk acoustic wave resonators; The input end (810), all the series resonators and the output end (820) are connected in series in sequence; one end of all the parallel resonators is grounded; any two adjacent series resonators are connected to an ungrounded end of a parallel resonator; and the series resonator connected to the output end (820) and the output end (820) are connected to an ungrounded end of a parallel resonator.

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