Temperature compensation type bulk acoustic wave resonator and manufacturing method thereof

Abstract

The invention discloses a temperature compensation type bulk acoustic wave resonator and a manufacturing method thereof, and belongs to the technical field of semiconductors, the temperature compensation type bulk acoustic wave resonator comprises a first substrate, a supporting layer, a bottom electrode, a piezoelectric layer, a temperature compensation layer and a top electrode which are stacked in sequence from bottom to top, and a cavity is formed in the middle of the face, connected with the supporting layer, of the first substrate; and the temperature compensation layer is made of a material with a positive frequency temperature coefficient. The temperature compensation layer is added on the piezoelectric layer aiming at the negative frequency temperature coefficient of a common piezoelectric material, and the inserted temperature compensation layer adopts a material with a positive frequency temperature coefficient to realize temperature compensation, so that the temperature compensation type bulk acoustic wave resonator has a lower temperature drift characteristic; the performance change of the bulk acoustic wave resonator and the filter constructed by the same along with the change of the working environment temperature can be reduced, and the working stability of the device can be enhanced; and the manufacturing method can be compatible with a CMOS process.

Description

Technical Field

[0001] The invention relates to a temperature-compensated bulk acoustic wave resonator and a manufacturing method thereof, belonging to the technical field of semiconductors. Background Art

[0002] With the development of communication technologies such as 5G, WiFi, and Bluetooth, as well as the improvement of system miniaturization and information function integration, the number of operating frequency bands that various mobile smart devices need to support is increasing, and the performance requirements of various systems for filters are also getting higher and higher. Among the existing filters, bulk acoustic wave filters are considered by the industry to be the filters most likely to achieve module integration because they have the excellent performance of dielectric filters and the compact size of surface acoustic wave filters, and have the advantages of high frequency and compatibility with traditional semiconductor CMOS processes. Based on factors such as preparation technology, thin film bulk acoustic wave filters have achieved great commercial success.

[0003] BAW filter is a device that uses the acoustic resonance of piezoelectric film in the thickness direction to achieve electrical frequency selection filtering. BAW resonator is the basic building block of BAW filter. A filter can be formed by cascading several BAW resonators according to a specific circuit topology. In the BAW filters that can be commercially mass-produced, since both the electrode material Mo and the piezoelectric material AlN have negative frequency temperature effects, the resonant frequency of the conventional Mo-AlN-Mo structured film BAW resonator will drift due to the influence of the external ambient temperature, and its frequency temperature coefficient is about 30×10 -6 ⁄℃, and this frequency-temperature drift characteristic will cause the electrical performance of the filter formed by it to change with the ambient temperature, which reduces the working performance of the filter at ambient temperature and the reliability in electrical applications. For example, it causes changes in the center frequency, insertion loss, in-band ripple and other performance of the filter, thereby limiting the application of bulk acoustic wave filters, especially in application scenarios with strict requirements on the passband insertion loss and rectangular coefficient of the filter. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, the present invention provides a temperature-compensated bulk acoustic wave resonator and a manufacturing method thereof. When the working environment temperature changes, the filtering performance changes little and the device has strong working stability.

[0005] The technical solution adopted by the present invention to solve its technical problem is: In a first aspect, the present application provides a temperature-compensated bulk acoustic wave resonator, which includes a first substrate, a supporting layer, a bottom electrode, a piezoelectric layer, a temperature-compensating layer and a top electrode stacked in sequence from bottom to top, wherein a cavity is provided in the middle of a side of the first substrate connected to the supporting layer, and the material of the temperature-compensating layer is a material having a positive frequency temperature coefficient.

[0006] The temperature-compensated BAW resonator provided in the present application has lower temperature drift characteristics, can reduce the performance change of the BAW resonator and the filter constructed therefrom when the working environment temperature changes, and is conducive to enhancing the working stability of the device.

[0007] As a preferred embodiment, the material of the temperature compensation layer is selected from silicon dioxide, phosphosilicate glass, borosilicate glass or borophosphorus glass.

[0008] As a preferred embodiment, the material of the support layer is selected from aluminum nitride, silicon carbide, silicon nitride or silicon dioxide.

[0009] As a preferred embodiment, the material of the first substrate is selected from silicon, silicon carbide or sapphire.

[0010] As a preferred embodiment, the material of the bottom electrode is selected from at least one of molybdenum, nickel, gold, aluminum, platinum, titanium, tungsten and ruthenium.

[0011] Optionally, the piezoelectric layer is a single layer of aluminum nitride, scandium aluminum nitride, zinc oxide, PZT piezoelectric ceramic, lithium niobate, lithium tantalate or BST piezoelectric ceramic.

[0012] Optionally, the piezoelectric layer is a stack of any multiple of aluminum nitride, aluminum scandium nitride, zinc oxide, PZT piezoelectric ceramics, lithium niobate, lithium tantalate, and BST piezoelectric ceramics.

[0013] As a preferred embodiment, the material of the top electrode is selected from at least one of molybdenum, nickel, gold, aluminum, platinum, titanium, tungsten and ruthenium.

[0014] As a preferred embodiment, the depth of the cavity is 2 μm to 30 μm.

[0015] In a second aspect, the present application provides a method for manufacturing a temperature-compensated bulk acoustic wave resonator, comprising the following steps: Forming grooves on a flat substrate by photolithography and etching to obtain a first substrate; sequentially preparing a piezoelectric layer, a bottom electrode, and a supporting layer on a second substrate; Bonding the first substrate to the second substrate by aligning the groove with the support layer, wherein the groove forms a cavity enclosed by the first substrate and the support layer; removing the second substrate to expose the piezoelectric layer; A temperature compensation layer is prepared on the piezoelectric layer; the material of the temperature compensation layer is a material with a positive frequency temperature coefficient; A top electrode is prepared on the temperature compensation layer to obtain the temperature compensation bulk acoustic wave resonator.

[0016] The temperature-compensated bulk acoustic wave resonator manufactured by the method has little change in filtering performance when the working environment temperature changes, and the device has strong working stability, and the manufacturing method is compatible with CMOS technology.

[0017] The beneficial effects of the present invention are as follows: in view of the fact that general piezoelectric materials have a negative frequency temperature coefficient, a temperature compensation layer is added on top of the piezoelectric layer. The inserted temperature compensation layer uses a material with a positive frequency temperature coefficient to achieve temperature compensation, so that the temperature-compensated bulk acoustic wave resonator has a lower temperature drift characteristic, and can reduce the performance change of the bulk acoustic wave resonator and the filter constructed therefrom when the working environment temperature changes, which is beneficial to enhancing the working stability of the device; and the manufacturing method is compatible with the CMOS process.

[0018] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or understood by practicing the present application. The purpose and other advantages of the present application can be realized and obtained by the structures particularly pointed out in the written description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of a temperature-compensated bulk acoustic wave resonator provided in an embodiment of the present application.

[0020] Figure 2 It is a schematic flow chart of a method for manufacturing a temperature-compensated bulk acoustic wave resonator provided in an embodiment of the present application.

[0021] Figure numerals: 1, first substrate; 10, groove; 11, cavity; 2, support layer; 3, bottom electrode; 4, piezoelectric layer; 5, temperature compensation layer; 6, top electrode; 7, second substrate. DETAILED DESCRIPTION

[0022] 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.

[0023] 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 positions or positional relationships based on the positions 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 device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, 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.

[0024] 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.

[0025] 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.

[0026] The disclosure below provides many different embodiments or examples to implement 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 simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed.

[0027] Unless otherwise specified, all technical and scientific terms used herein have the standard meaning in the field to which the claimed subject matter belongs. If there are multiple definitions for a term, the definition herein shall prevail.

[0028] Since the electrodes and piezoelectric layers are usually made of materials with negative frequency temperature coefficients, the center frequency, insertion loss, and in-band ripple of general BAW resonators vary greatly at different temperatures, making them difficult to apply to scenarios where the ambient temperature varies greatly.

[0029] Reference Figure 1 An embodiment of the present application provides a temperature-compensated bulk acoustic wave resonator, which includes a first substrate 1, a support layer 2, a bottom electrode 3, a piezoelectric layer 4, a temperature-compensating layer 5 and a top electrode 6 stacked in sequence from bottom to top. The first substrate 1 is provided with a cavity 11 in the middle of a side connected to the support layer 2, and the material of the temperature-compensating layer 5 is a material with a positive frequency temperature coefficient.

[0030] The BAW resonator provided in the embodiment of the present application has a low temperature drift characteristic, which can reduce the performance change of the BAW resonator and the filter constructed therefrom when the working environment temperature changes, and enhance the working stability of the device.

[0031] Accordingly, an embodiment of the present application also provides a device manufacturing process that is compatible with the CMOS process as follows.

[0032] Reference Figure 2 The present invention provides a method for manufacturing a temperature-compensated bulk acoustic wave resonator, comprising the following steps: S1: A groove 10 is formed on a flat substrate by photolithography and etching to obtain a first substrate 1.

[0033] S2: The piezoelectric layer 4, the bottom electrode 3 and the support layer 2 are sequentially prepared on the second substrate 7.

[0034] S3 : bonding the first substrate 1 and the second substrate 7 with the groove 10 aligned with the support layer 2 , wherein the groove 10 forms a cavity 11 in the enclosure of the first substrate 1 and the support layer 2 .

[0035] S4: removing the second substrate 7 to expose the piezoelectric layer 4 .

[0036] S5: preparing a temperature compensation layer 5 on the piezoelectric layer 4; the material of the temperature compensation layer 5 is a material with a positive frequency temperature coefficient; S6: preparing a top electrode on the temperature compensation layer 5 to obtain a temperature compensation bulk acoustic wave resonator.

[0037] This manufacturing method is compatible with standard CMOS processes. In the process of manufacturing a device containing a temperature compensation layer by conventional processes, the temperature compensation layer is exposed to the outside, and the corrosive liquid in the process is easy to corrode the temperature compensation layer material and destroy the structure of the temperature compensation layer, which leads to a deviation between the temperature compensation effect and the design effect, and causes the energy attenuation of the main mode of the resonator and leads to a reduction in the quality factor. In the manufacturing method provided in the embodiment of the present application, the formation of the cavity structure is achieved by flip-chip bonding, which avoids the sacrificial layer in the conventional cavity structure and the process of removing the sacrificial layer, and the temperature compensation layer 5 and the top electrode 6 are continuously formed after the flip-chip bonding is completed, reducing the impact on the temperature compensation layer during the processing. The whole method is simple in process and easy to process, which can effectively improve the reliability and stability of the device.

[0038] In step S1 , the depth of the groove formed by photolithography and etching is 2 μm to 30 μm, and then the depth of the cavity 11 formed after flip-chip bonding is 2 μm to 30 μm.

[0039] When preparing the piezoelectric layer 4 in step S2, it can be achieved through MBE (molecular beam epitaxy), PLD (pulsed laser deposition), MOCVD (metal organic chemical vapor deposition) and other technologies and their combination.

[0040] When preparing the bottom electrode in step S2, it can be realized by magnetron sputtering. Similarly, when preparing the top electrode in step S6, it can also be realized by magnetron sputtering.

[0041] When preparing the support layer in step S2, it can be achieved by LPCVD (low pressure chemical vapor deposition).

[0042] In step S4, the second substrate may be removed using a KOH solution.

[0043] In step S5, the temperature compensation layer may be deposited by PECVD (plasma enhanced chemical vapor deposition).

[0044] In some embodiments, the material of the temperature compensation layer 5 includes, but is not limited to, materials with positive temperature coefficients such as SiO2, PSG (phosphosilicate glass), BSG (borosilicate glass), and BPSG (borophosphosilicate glass). These materials have a positive frequency temperature coefficient, which can form a complementary effect with the negative temperature coefficient of the piezoelectric material, thereby offsetting part of the temperature drift. Preferably, the material of the temperature compensation layer 5 is a material such as PSG, BSG, BPSG, etc., which can adjust the frequency temperature coefficient by changing the doping content.

[0045] In some embodiments, the material of the support layer 2 is selected from any one of AlN, SiC, Si3N4, SiO2, etc. These materials have good mechanical strength and thermal stability, can provide support for the piezoelectric layer, and reduce the influence of structural deformation on resonance performance at different temperatures.

[0046] In some embodiments, the material of the first substrate 1 includes but is not limited to Si, SiC, sapphire, etc., and is preferably a high-resistance silicon substrate material.

[0047] In some embodiments, the material of the bottom electrode 3 can be selected from any one of Mo, Ni, Au, Al, Pt, Ti, W, and Ru, or any combination of multiple materials, which can significantly improve the conductivity of the BAW resonator and the stability of the electrode. Similarly, the material of the top electrode 6 can also be selected from at least one of molybdenum, nickel, gold, aluminum, platinum, titanium, tungsten, and ruthenium. When these highly conductive materials are selected as the bottom electrode and the top electrode, the resistance loss can be reduced during the operation of the device, thereby improving the Q value (quality factor) of the BAW resonator and improving the overall performance of the filter. This is crucial to maintaining the BAW resonator in good working condition in the high frequency band.

[0048] The material of the piezoelectric layer 4 includes, but is not limited to, single crystal or polycrystalline AlN, AlScN, ZnO, PZT (lead titanate) piezoelectric ceramics, LiNbO3, LiTaO3, BST (barium strontium titanate) piezoelectric ceramics and other thin film materials with piezoelectric effect, and may also be a composite thin film material composed of several of these materials. For example, the piezoelectric layer 4 is a single layer of aluminum nitride, aluminum scandium nitride, zinc oxide, PZT piezoelectric ceramics, lithium niobate, lithium tantalate or BST piezoelectric ceramics. Alternatively, the piezoelectric layer 4 is a stack of any of aluminum nitride, aluminum scandium nitride, zinc oxide, PZT piezoelectric ceramics, lithium niobate, lithium tantalate, and BST piezoelectric ceramics.

[0049] Example 1 The present invention provides a temperature-compensated bulk acoustic wave resonator, which is manufactured according to the following steps: (1) A silicon substrate is provided, and a groove is formed on the substrate by photolithography, wherein the groove has a depth of 30 μm, thereby obtaining a first substrate.

[0050] (2) Providing a second substrate (silicon) and preparing a high-quality AlN thin film on the second substrate by MBE technology to form a piezoelectric layer.

[0051] (3) A Mo bottom electrode is prepared on the piezoelectric layer obtained in (2) by magnetron sputtering or other techniques.

[0052] (4) A silicon carbide support layer is fabricated on the bottom electrode film obtained in (3) by using LPCVD or other techniques.

[0053] (5) The structure obtained in (4) is bonded to a first substrate having a groove etched therein by a flip-chip bonding process to form a cavity structure.

[0054] (6) The second substrate in (5) is corroded using a solution such as KOH to remove the second substrate.

[0055] (7) PSG is grown on the AlN piezoelectric layer obtained after (6) by PECVD as a temperature compensation layer.

[0056] (8) Prepare the Mo top electrode structure on the temperature compensation layer by magnetron sputtering and other techniques.

[0057] Example 2 The present invention provides a temperature-compensated bulk acoustic wave resonator, which is manufactured according to the following steps: (1) A silicon carbide substrate is provided, and a groove is formed on the substrate by photolithography, wherein the groove has a depth of 10 μm, thereby obtaining a first substrate.

[0058] (2) Providing a second substrate (silicon), preparing a ZnO thin film on the second substrate by PLD technology, and then preparing a LiNbO3 thin film by PLD technology to form a piezoelectric layer.

[0059] (3) A Ni bottom electrode is prepared on the piezoelectric layer obtained in (2) by magnetron sputtering or other techniques.

[0060] (4) A silicon nitride support layer is fabricated on the bottom electrode film obtained in (3) by using LPCVD or other techniques.

[0061] (5) The structure obtained in (4) is bonded to a first substrate having a groove etched therein by a flip-chip bonding process to form a cavity structure.

[0062] (6) The second substrate in (5) is corroded using a solution such as KOH to remove the second substrate.

[0063] (7) BPSG is grown on the AlN piezoelectric layer obtained after (6) by PECVD as a temperature compensation layer.

[0064] (8) Prepare the Ni top electrode structure on the temperature compensation layer by magnetron sputtering and other techniques.

[0065] The embodiment of the present application is aimed at piezoelectric materials with negative frequency temperature coefficients. The inserted temperature compensation layer uses materials with positive temperature characteristics to achieve temperature compensation. For temperature compensation layer materials such as PSG, BSG, and BPSG, the frequency temperature coefficient can be further controlled by adjusting the doping content, and can match bulk acoustic wave resonators of various design specifications, thereby obtaining a device with high temperature stability.

[0066] In the description of this specification, the description with reference to the terms "one embodiment", "certain embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means 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 representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0067] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A temperature-compensated bulk acoustic wave resonator, characterized in that: The invention comprises, from bottom to top, a first substrate (1), a support layer (2), a bottom electrode (3), a piezoelectric layer (4), a temperature compensation layer (5) and a top electrode (6) which are stacked in sequence, wherein a cavity (11) is provided in the middle of a surface of the first substrate (1) connected to the support layer (2), and the temperature compensation layer (5) is made of a material having a positive frequency temperature coefficient.

2. The temperature-compensated bulk acoustic wave resonator according to claim 1, characterized in that: The material of the temperature compensation layer (5) is selected from silicon dioxide, phosphosilicate glass, borosilicate glass or borophosphorus glass.

3. The temperature-compensated bulk acoustic wave resonator according to claim 1, characterized in that: The material of the support layer (2) is selected from aluminum nitride, silicon carbide, silicon nitride or silicon dioxide.

4. The temperature-compensated bulk acoustic wave resonator according to claim 1, characterized in that: The material of the first substrate (1) is selected from silicon, silicon carbide or sapphire.

5. The temperature-compensated bulk acoustic wave resonator according to claim 1, characterized in that: The material of the bottom electrode (3) is selected from at least one of molybdenum, nickel, gold, aluminum, platinum, titanium, tungsten and ruthenium.

6. The temperature-compensated bulk acoustic wave resonator according to claim 1, characterized in that: The piezoelectric layer (4) is a single layer of aluminum nitride, aluminum scandium nitride, zinc oxide, PZT piezoelectric ceramics, lithium niobate, lithium tantalate or BST piezoelectric ceramics.

7. The temperature-compensated bulk acoustic wave resonator according to claim 1, characterized in that: The piezoelectric layer (4) is a stack of any of aluminum nitride, aluminum scandium nitride, zinc oxide, PZT piezoelectric ceramics, lithium niobate, lithium tantalate, and BST piezoelectric ceramics.

8. The temperature-compensated bulk acoustic wave resonator according to claim 1, characterized in that: The material of the top electrode (6) is selected from at least one of molybdenum, nickel, gold, aluminum, platinum, titanium, tungsten and ruthenium.

9. The temperature-compensated bulk acoustic wave resonator according to claim 1, characterized in that: The depth of the cavity (11) is 2 μm to 30 μm.

10. A method for manufacturing a temperature-compensated bulk acoustic wave resonator, characterized in that: The following steps are involved: Forming a groove (10) on a flat substrate by photolithography and etching to obtain a first substrate (1); A piezoelectric layer (4), a bottom electrode (3), and a support layer (2) are sequentially prepared on a second substrate (7); Bonding the first substrate (1) and the second substrate (7) so that the groove (10) is aligned with the support layer (2), the groove (10) forming a cavity (11) enclosed by the first substrate (1) and the support layer (2); removing the second substrate (7) to expose the piezoelectric layer (4); A temperature compensation layer (5) is prepared on the piezoelectric layer (4); the material of the temperature compensation layer (5) is a material with a positive frequency temperature coefficient; A top electrode is prepared on the temperature compensation layer (5) to obtain the temperature compensation bulk acoustic wave resonator.

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