Bulk acoustic wave resonator, filter and communication equipment

Abstract

The utility model provides a bulk acoustic wave resonator, a filter and communication equipment. The bulk acoustic wave resonator includes a substrate and an acoustic wave reflection region formed in or on the substrate; a lower electrode formed on the acoustic wave reflection region; the temperature compensation layer is formed on the lower electrode; the first seed crystal layer is formed on the temperature compensation layer, the first seed crystal layer is provided with a first part and a second part, the first part is in contact with the upper surface of the temperature compensation layer, and the second part is in contact with the upper surface of the substrate, the side face of the lower electrode, the upper surface of the lower electrode and the side face of the temperature compensation layer at the same time; the area of the first part is smaller than that of the second part; a piezoelectric layer formed on the first seed crystal layer; and the upper electrode is formed on the piezoelectric layer.

Description

Technical Field

[0001] The utility model relates to radio frequency technology, and more specifically to a bulk acoustic wave resonator, a filter and a communication device. Background Art

[0002] With the development of communication technology, filters are an indispensable component in portable and other types of communication equipment. Filters are mainly used to filter signals and realize the functions of receiving and transmitting signals.

[0003] In the prior art, filters formed by bulk acoustic wave resonators are compatible with standard integrated manufacturing technology in terms of process, and have the characteristics of small size, low insertion loss, high frequency, and good rectangular coefficient, and are more suitable for application in portable communication devices.

[0004] See also Figure 1 , Figure 1 FIG. 2 shows a schematic diagram of the structure of a BAW resonator in the prior art. Figure 1 As shown, the BAW resonator generally includes a substrate 100, a cavity 101, a lower electrode 102, a piezoelectric layer 103, and an upper electrode 104, wherein the lower electrode 102, the upper electrode 104, and the piezoelectric layer 103 form a sandwich structure. When an electrical signal is applied between the upper and lower electrodes, the reverse piezoelectric effect causes the piezoelectric layer 103 to mechanically expand or contract due to the polarization of the piezoelectric material. The expansion and contraction of the piezoelectric layer 103 generates acoustic waves that propagate in various directions and are converted into electrical signals through the piezoelectric effect.

[0005] Since the insertion loss and passband frequency of the filter will be affected by temperature changes, and the piezoelectric material and electrode material of the BAW resonator in the filter usually have a negative frequency temperature drift coefficient, as the temperature rises, the stiffness of the piezoelectric material and the electrode material will decrease accordingly, resulting in a decrease in the speed of sound waves, and then the passband frequency of the filter. Therefore, in order to avoid the influence of temperature changes on the filter, temperature compensation needs to be introduced. Therefore, it is desirable in the industry to provide a BAW resonator that can provide stable temperature compensation. Utility Model Content

[0006] In view of the above technical problems, the utility model designs a bulk acoustic wave resonator, a filter and a communication device with stable temperature compensation.

[0007] A brief overview of the present invention will be given below in order to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify key or important parts of the present invention, nor is it intended to limit the scope of the present invention. Its purpose is simply to present certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0008] According to one aspect of the utility model, a bulk acoustic wave resonator is provided, comprising: a substrate and an acoustic wave reflection region formed in or on the substrate; a lower electrode, the lower electrode being formed on the acoustic wave reflection region; a temperature compensation layer, the temperature compensation layer being formed on the lower electrode; a first seed layer, the first seed layer being formed on the temperature compensation layer, the first seed layer having a first portion and a second portion, the first portion being in contact with an upper surface of the temperature compensation layer, the second portion being in contact with an upper surface of the substrate, a side surface of the lower electrode, an upper surface of the lower electrode and a side surface of the temperature compensation layer at the same time, the area of ​​the first portion being smaller than the area of ​​the second portion; a piezoelectric layer, the piezoelectric layer being formed on the first seed layer;

[0009] An upper electrode is formed on the piezoelectric layer.

[0010] Furthermore, a projection area of ​​the temperature compensation layer on the lower surface of the substrate is smaller than a projection area of ​​the lower electrode on the lower surface of the substrate, and is larger than a projection area of ​​the upper electrode on the lower surface of the substrate.

[0011] Furthermore, a second seed crystal layer is provided between the lower surface of the temperature compensation layer and the upper surface of the lower electrode.

[0012] Furthermore, the thickness of the first seed layer is 200 angstroms to 400 angstroms.

[0013] Furthermore, the grains of the first seed crystal layer are smaller than 0.2 micrometers×0.2 micrometers.

[0014] Furthermore, the thickness of the second seed layer is 200 angstroms to 400 angstroms.

[0015] Furthermore, the grains of the second seed crystal layer are smaller than 0.2 micrometers×0.2 micrometers.

[0016] Furthermore, the BAW resonator further includes a mass load layer, a frame structure and / or a passivation layer.

[0017] According to another aspect of the present invention, a filter is provided, the filter comprising any one of the aforementioned BAW resonators.

[0018] According to another aspect of the present invention, a communication device is provided, characterized in that: the communication device has the aforementioned filter.

[0019] The solution of the utility model can at least help achieve one of the following effects: it can better perform temperature compensation on the filter composed of the bulk acoustic wave resonator provided by the utility model, reduce the impact of temperature changes on the insertion loss and passband frequency of the filter, and improve the performance of the filter. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The specific contents of the utility model are described below with reference to the accompanying drawings, which will help to more easily understand the above and other purposes, features and advantages of the utility model. The accompanying drawings are only for illustrating the principles of the utility model. The sizes and relative positions of the units in the accompanying drawings do not need to be drawn in proportion.

[0021] Figure 1 A schematic diagram showing the structure of a bulk acoustic wave resonator in the prior art is shown;

[0022] Figure 2 A schematic structural diagram of a bulk acoustic wave resonator provided by the utility model is shown;

[0023] Figure 3 A modified implementation of the bulk acoustic wave resonator structure provided by the utility model is shown;

[0024] Figure 4 A comparative example of the bulk acoustic wave resonator structure provided by the utility model is shown;

[0025] Figure 5 A schematic diagram showing the morphology of the temperature compensation layer being corroded in the comparative example. DETAILED DESCRIPTION

[0026] Below, exemplary embodiments of the present invention will be described in conjunction with the accompanying drawings. For the sake of clarity and conciseness, not all features of implementing the present invention are described in the specification. However, it should be understood that many decisions specific to the present invention may be made in the process of developing any such implementation of the present invention in order to achieve the specific goals of the developer, and these decisions may vary from one invention to another.

[0027] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only the device structure closely related to the solution according to the present invention is shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0028] In general, it should be understood that the drawings and the various elements depicted therein are not drawn to scale. Furthermore, the use of relative terms such as "above," "below," "top," "bottom," "upper," and "lower" to describe the relationship of various elements to one another should be understood to encompass different orientations of the device and / or elements in addition to the orientation depicted in the drawings.

[0029] It should be understood that the present invention is not limited to the described implementation forms due to the following description with reference to the accompanying drawings. Herein, where feasible, features between different embodiments may be replaced or borrowed, and one or more features may be omitted in one embodiment.

[0030] See also Figure 2, Figure 2 A structural schematic diagram of a bulk acoustic wave resonator provided by the utility model is shown.

[0031] The BAW resonator at least includes a substrate 1000, an acoustic wave reflection region 1100, a lower electrode 2000, a temperature compensation layer 3000 formed on the lower electrode 2000, a first seed layer 4000 formed on the temperature compensation layer 3000, a piezoelectric layer 5000 formed on the first seed layer 4000, and an upper electrode 6000 formed on the piezoelectric layer 5000. There is at least an overlapping region between the acoustic wave reflection region 1100, the lower electrode 2000, the temperature compensation layer 3000, the first seed layer 4000, the piezoelectric layer 5000 and the upper electrode 6000, and the overlapping region is defined as the resonance region of the BAW resonator.

[0032] Specifically, the substrate 1000 may be, for example, silicon (Si), gallium arsenide (GaAs), indium phosphide (InP), glass, sapphire, aluminum oxide, or the like. 、 SiC and other materials compatible with the semiconductor process. The acoustic wave reflection region 1100 is formed in or on the substrate 1000. Exemplarily, the acoustic wave reflection region 1100 may be composed of a cavity or a Bragg reflection layer formed in the substrate 1000. It is understandable that the present invention does not further limit the shape of the acoustic wave reflection region 1100. The projection contour of the shape of the acoustic wave reflection region 1100 on the lower surface of the substrate 1000 may be an irregular shape, or a regular polygon such as a triangle, rectangle, pentagon, hexagon, octagon, etc.

[0033] The lower electrode 2000 is formed on the substrate 1000 to cover the acoustic wave reflection area 1100. The lower electrode 2000 can be a single layer or a multilayer. The lower electrode 2000 can be formed of one or more conductive materials, such as various metals compatible with semiconductor processes including tungsten (W), molybdenum (Mo), iridium (Ir), aluminum (Al), platinum (Pt), ruthenium (Ru), niobium (Nb) or hafnium (Hf). The utility model does not further limit the shape of the lower electrode 2000. The projection contour of the shape of the lower electrode 2000 on the lower surface of the substrate 1000 can be an irregular shape, or a regular polygon such as a triangle, rectangle, pentagon, hexagon, octagon, etc.

[0034] The temperature compensation layer 3000 is formed on the lower electrode 2000. The material of the temperature compensation layer 3000 is a material with a positive frequency temperature drift coefficient. Exemplarily, the material of the temperature compensation layer 3000 may be silicon dioxide. When the temperature of the material with a positive frequency temperature drift coefficient increases, the stiffness of the material will increase. Therefore, the temperature characteristics of the material can be compensated by setting the temperature compensation layer 3000 to compensate for the decrease in the sound velocity caused by the decrease in the stiffness of the piezoelectric layer 5000 material and the upper electrode 6000 / lower electrode 2000 material of the bulk acoustic wave resonator, thereby preventing the filter from generating frequency drift. The shape of the temperature compensation layer 3000 can be an irregular shape, or a regular polygon such as a triangle, rectangle, pentagon, hexagon, octagon, etc.

[0035] The first seed layer 4000 is formed on the temperature compensation layer 3000. The material of the first seed layer 4000 can be the same as the material of the piezoelectric layer 5000. The thickness of the first seed layer 4000 is set to have the effect of fixing the crystal orientation. Exemplarily, the thickness of the first seed layer 4000 is between 200 angstroms and 400 angstroms. Further, based on the specific definition of the area of ​​the temperature compensation layer 3000 in the utility model, the first seed layer 4000 has a first portion 4100 in contact with the upper surface of the temperature compensation layer 3000, and a second portion 4200 in contact with the upper surface of the substrate 1000, the side of the lower electrode 2000, a portion of the upper surface of the lower electrode 2000, and the side of the temperature compensation layer 3000. The area of ​​the first portion 4100 of the first seed crystal layer 4000 is smaller than the area of ​​the second portion 4200 . Further, the first seed crystal layer 4000 is preferably a compressed seed crystal layer, and the grain size thereof is smaller than 0.2 microns×0.2 microns.

[0036] For further information, see Figure 3 , Figure 3 FIG. 2 shows a modified implementation of the BAW resonator structure provided by the present utility model. Figure 3 As shown, in the structure of the bulk acoustic wave resonator provided by the utility model, a second seed crystal layer 8000 is also provided on the lower surface of the temperature compensation layer 3000. The thickness of the second seed crystal layer 8000 is set to have the effect of fixing the crystal orientation. Exemplarily, the thickness of the second seed crystal layer 8000 is between 200 angstroms and 400 angstroms. The material of the second seed crystal layer 8000 can be the same as the material of the piezoelectric layer 5000. The area of ​​the second seed crystal layer 8000 is equal to the lower surface area of ​​the temperature compensation layer 3000. The second seed crystal layer 8000 is preferably a compressed seed crystal layer, and its grain size is less than 0.2 microns*0.2 microns.

[0037] Continue to see Figure 2The piezoelectric layer 5000 is conformally formed on the first seed layer 4000. The piezoelectric layer 5000 may be formed of any piezoelectric material compatible with semiconductor processes, such as aluminum nitride (AlN), aluminum nitride doped with rare earth such as scandium or strontium, or zirconate titanate (PZT).

[0038] The upper electrode 6000 is arranged on the piezoelectric layer 5000. The upper electrode 6000 can be a single layer or a multilayer. The upper electrode 6000 can be formed of one or more conductive materials, such as various metals compatible with semiconductor processes including tungsten (W), molybdenum (Mo), iridium (Ir), aluminum (Al), platinum (Pt), ruthenium (Ru), niobium (Nb) or hafnium (Hf). The material of the upper electrode 6000 and the lower electrode 2000 can be the same or different. The projection contour of the shape of the upper electrode 6000 on the lower surface of the substrate 1000 can be an irregular shape, or a regular polygon such as a triangle, rectangle, pentagon, hexagon, octagon, etc.

[0039] In the bulk acoustic wave resonator structure, the projection area of ​​the temperature compensation layer 3000 on the lower surface of the substrate 1000 is smaller than the projection area of ​​the lower electrode 2000 on the lower surface of the substrate 1000, and the projection area of ​​the temperature compensation layer 3000 on the lower surface of the substrate 1000 is larger than the projection area of ​​the upper electrode 6000 on the lower surface of the substrate 1000.

[0040] Further, the BAW resonator provided by the utility model may also include a mass load layer, a frame structure, etc. formed on the upper electrode 6000 and / or the lower electrode 2000. Alternatively, the BAW resonator provided by the utility model may also form a passivation layer 7000 on the upper electrode 6000. The mass load layer and the upper electrode 6000 and / or the lower electrode 2000 may be formed integrally or separately. The material of the mass load layer may be the same as that of the upper electrode 6000 and / or the lower electrode 2000. The passivation layer covers the upper electrode 6000, and the material of the passivation layer 7000 may be the same as that of the piezoelectric layer 5000.

[0041] The design concept and advantages of the bulk acoustic wave resonator provided by the utility model are further described in detail below in conjunction with comparative examples:

[0042] See also Figure 4 , Figure 4 FIG. 2 shows a comparative example of the bulk acoustic wave resonator structure provided by the present utility model. Figure 4 As shown in , the difference between the BAW resonator provided by the comparative example and the present invention is that no seed crystal layer is provided, and the rest of the configuration is the same as the structural features of the present invention. Figure 4In the structure shown, the grains of the temperature compensation layer 3000 formed by thermal decomposition are relatively large, resulting in a poor lattice of the piezoelectric layer 5000 formed on its upper surface, making the corrosion resistance of this part of the piezoelectric layer 5000 poor, resulting in poor process compatibility of the temperature compensation layer 3000. Specifically, in the later process of the BAW resonator process, the temperature compensation layer 3000 is easily damaged. Figure 5 , Figure 5 The morphology of the temperature compensation layer being etched in the comparative example is shown in FIG. 1 . The etching solution (such as HF etching solution) used in the subsequent process of the BAW resonator (such as the process of releasing the cavity of the substrate 1000) can cause the temperature compensation layer 3000 to be partially etched at the same time, such as Figure 5 As shown at A and B in the figure, the performance stability and structural integrity of the temperature compensation layer 3000 are affected.

[0043] To this end, the area of ​​the temperature compensation layer 3000 is first designed in the utility model. That is, the area of ​​the temperature compensation layer 3000 is set as follows: the projected area of ​​the temperature compensation layer 3000 on the lower surface of the substrate 1000 is smaller than the projected area of ​​the lower electrode 2000 on the lower surface of the substrate 1000, and the projected area of ​​the temperature compensation layer 3000 on the lower surface of the substrate 1000 is larger than the projected area of ​​the upper electrode 6000 on the lower surface of the substrate 1000. By specifically limiting the area size of the temperature compensation layer 3000, on the one hand, the effective area of ​​the bulk acoustic wave resonator can be guaranteed, and on the other hand, the lattice direction of the first seed layer 4000 can also be guaranteed.

[0044] Secondly, the utility model introduces a first seed layer 4000, and the first seed layer 4000 uses a compressed seed layer, and its grain size is less than 0.2 microns × 0.2 microns. When the first seed layer 4000 is formed in the BAW resonator structure, since the first seed layer 4000 in the utility model can be formed by conformal deposition, it is not necessary to pattern the seed layer as in the prior art, thereby making the manufacturing process simpler.

[0045] Again, in the utility model, the area of ​​the first part 4100 of the first seed crystal layer 4000 is relatively small, so the lattice of the first part 4100 of the first seed crystal layer is affected by the lattice of the second part 4200 of the first seed crystal layer, thereby better ensuring the lattice direction of the first seed crystal layer 4000, and the first seed crystal layer 4000 can further eliminate the local lattice defect problem of the temperature compensation layer 3000. Subsequently, during the deposition process of the piezoelectric layer 5000, the lattice growth of the piezoelectric layer 5000 formed on the first part 4100 of the first seed crystal layer will not be affected by the larger grains in the temperature compensation layer 3000, but will be affected by the lattice of the first part 4100 of the first seed crystal layer, thereby avoiding the deterioration of the lattice of the piezoelectric layer 5000 of this part, ensuring the lattice and density of the piezoelectric layer 5000, and then in turn affecting the temperature compensation layer 3000, ensuring its performance and structural integrity, and ensuring the feasibility of the BAW resonator process and the stability of the BAW resonator structure.

[0046] Thirdly, in the present invention, a second seed layer 8000 is introduced between the temperature compensation layer 3000 and the lower electrode 2000 , and the second seed layer 8000 can be lattice matched with the temperature compensation layer 3000 formed thereon.

[0047] The BAW resonator provided by the utility model is through the careful design of the temperature compensation layer 3000, the first seed crystal layer 4000 or the temperature compensation layer 3000, the first seed crystal layer 4000 and the second seed crystal layer 8000, so that the BAW resonator provided by the utility model can better perform temperature compensation on the filter composed of the BAW resonator than the BAW resonator of the comparative example, reduce the influence of temperature changes on the insertion loss and passband frequency of the filter, and improve the performance of the filter.

[0048] The utility model also provides a filter, which can be used in the field of portable communication devices such as mobile phones, personal digital assistants (PDAs), and electronic game devices. The filter can include any one of the acoustic wave resonators in the above-mentioned embodiments.

[0049] The utility model also provides a filter that can be used to prepare radio frequency devices such as duplexers and multiplexers, and the radio frequency devices can be used in communication devices such as mobile phones, personal digital assistants (PDAs), personal wearable devices, and electronic game devices.

[0050] The present invention is described above in conjunction with specific implementation schemes, but those skilled in the art should be aware that these descriptions are exemplary and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make various modifications and variations to the present invention based on the spirit and principles of the present invention, and these modifications and variations are also within the scope of the present invention.

Claims

1. A bulk acoustic wave resonator, characterized in that: include: A substrate and a sound wave reflecting region formed in or on the substrate; A lower electrode formed on the acoustic wave reflection area; a temperature compensation layer, the temperature compensation layer being formed on the lower electrode; a first seed layer, wherein the first seed layer is formed on the temperature compensation layer, the first seed layer comprises a first portion and a second portion, the first portion contacts the upper surface of the temperature compensation layer, the second portion contacts the upper surface of the substrate, the side surface of the lower electrode, the upper surface of the lower electrode and the side surface of the temperature compensation layer at the same time, and the area of ​​the first portion is smaller than the area of ​​the second portion; a piezoelectric layer formed on the first seed layer; An upper electrode is formed on the piezoelectric layer.

2. The BAW resonator according to claim 1, wherein: The projected area of ​​the temperature compensation layer on the lower surface of the substrate is smaller than the projected area of ​​the lower electrode on the lower surface of the substrate, and larger than the projected area of ​​the upper electrode on the lower surface of the substrate.

3. The bulk acoustic wave resonator according to claim 1 or 2, characterized in that: A second seed layer is provided between the lower surface of the temperature compensation layer and the upper surface of the lower electrode.

4. The bulk acoustic wave resonator according to claim 1 or 2, characterized in that: The thickness of the first seed layer is 200 angstroms to 400 angstroms.

5. The BAW resonator according to claim 4, characterized in that: The grains of the first seed crystal layer are smaller than 0.2 micrometers×0.2 micrometers.

6. The BAW resonator according to claim 3, characterized in that: The thickness of the second seed layer is 200 angstroms to 400 angstroms.

7. The BAW resonator according to claim 6, characterized in that: The grains of the second seed crystal layer are smaller than 0.2 micrometers×0.2 micrometers.

8. The bulk acoustic wave resonator according to claim 1 or 2, characterized in that: The BAW resonator further comprises a mass loading layer, a frame structure and / or a passivation layer.

9. A filter, characterized in that: The filter comprises the bulk acoustic wave resonator according to any one of claims 1-8.

10. A communication device, characterized in that: The communication device comprises the filter as claimed in claim 9.

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