Surface acoustic wave transducer and device comprising same
By designing the envelope of the step trace and the corresponding electrode finger side edge position change structure in the interdigital electrode of the surface acoustic wave transducer, the problem of lateral energy leakage in the resonator is solved, and the performance of the filter is significantly improved.
Patent Information
- Application Number
- CN202311377015.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-10-23
- Publication Date
- 2025-04-25
Smart Images
Figure CN119891996A_ABST
Abstract
Description
Technical Field
[0001] Embodiments of the present disclosure relate to the field of semiconductors, and in particular, to a surface acoustic wave transducer and a device comprising the same. Background Art
[0002] As communication technology develops from 2G to 5G, the number of communication frequency bands has gradually increased (from 4 frequency bands in 2G to more than 50 frequency bands in 5G). In order to improve the compatibility of smartphones with different communication standards, the amount of filters required for 5G smartphones will increase significantly, driving large-scale growth in the filter market. The RF filter currently widely used in wireless communication terminals is the surface acoustic wave filter, which is responsible for filtering the RF signals of the receiving and transmitting channels and outputting signals of specific frequencies from the multiple input RF signals. In the structure of the surface acoustic wave filter, the most important unit is the resonator, so different resonator structures will have a huge impact on the final performance of the surface acoustic wave filter.
[0003] Figure 1 is a schematic diagram of the structure of the current resonator. Figure 1 As shown, the resonator includes interdigitated electrodes and reflectors 31 located on both sides of the interdigitated electrodes. The interdigitated electrodes include a first bus bar 11 and a second bus bar 21. A plurality of first electrode fingers 12 and a plurality of first virtual fingers 13 are alternately arranged on the first bus bar 11. A plurality of second electrode fingers 22 and a plurality of second virtual fingers 23 are alternately arranged on the second bus bar 21. In the propagation direction of the surface acoustic wave (i.e., the horizontal direction in the figure), the plurality of first electrode fingers 12 and the plurality of second electrode fingers 22 are arranged in an alternating manner. The first electrode fingers 12 and the second virtual fingers 23 are arranged opposite to each other and there is a gap. The second electrode fingers 22 and the first virtual fingers 13 are arranged opposite to each other and there is a gap. The connecting line of the ends of all the first electrode fingers 12 (or the connecting line of the gaps at the ends of all the first electrode fingers 12) and the connecting line of the ends of all the second electrode fingers 22 (or the connecting line of the gaps at the ends of all the second electrode fingers 22) are all straight lines along the propagation direction of the surface acoustic wave. Figure 1 The resonator shown has the problem of lateral energy leakage of acoustic waves, which will cause energy loss in the filter and reduce the filter performance. Summary of the invention
[0004] The present disclosure is proposed to alleviate or solve at least one aspect of the above-mentioned problems in the prior art.
[0005] According to one aspect of an embodiment of the present disclosure, a surface acoustic wave transducer is provided, comprising:
[0006] Piezoelectric layer;
[0007] The interdigitated electrodes are arranged on the surface of the piezoelectric layer, and include: a first bus bar and a plurality of first electrode fingers connected to the first bus bar, a second bus bar and a plurality of second electrode fingers connected to the second bus bar,
[0008] in:
[0009] The interdigitated electrode comprises at least one envelope unit, wherein the envelope unit has a first envelope defined by ends of the plurality of first electrode fingers and / or a second envelope defined by ends of the plurality of second electrode fingers, and at least a portion of the first envelope and / or the second envelope is a step trace;
[0010] For the bus bar in the first bus bar and / or the second bus bar that is close to the step trace, there is a corresponding trend in the position change of at least a portion of the edge of the side edge of the electrode finger in the length direction of the electrode finger and a corresponding trend in the position change of the envelope line close to at least a portion of the edge in the length direction of the electrode finger.
[0011] According to one aspect of an embodiment of the present disclosure, a device is provided, comprising the above-mentioned surface acoustic wave transducer. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The following description and accompanying drawings may better help understand these and other features and advantages of various embodiments disclosed in the present disclosure, wherein the same reference numerals in the drawings always represent the same components, wherein:
[0013] Figure 1 is a schematic top view of a known resonator;
[0014] Figure 2 is a schematic top view of a surface acoustic wave transducer according to an exemplary embodiment of the present disclosure;
[0015] Figure 3 for Figure 2 A schematic cross-sectional view of a surface acoustic wave transducer;
[0016] Figure 4 Shows Figure 2 The envelope and symmetry center of the SAW transducer;
[0017] Figure 5 for Figure 2 A schematic diagram of the interdigitated electrode portion of a surface acoustic wave transducer, showing various dimensions;
[0018] Figure 6 The comparison chart of the test results shows the Figure 1 and Figure 2 The curve of the real part of the admittance of the SAW transducer changing with frequency;
[0019] Figure 7 The comparison chart of the test results shows Figure 1 and Figure 2 The curve of the quality factor of the surface acoustic wave transducer changing with frequency;
[0020] Figure 8 and Fig. 9 for Figure 2 Variations of the SAW transducer showing different numbers of periods;
[0021] Figure 10-13 for Figure 2 Variations of the SAW transducer showing different shapes of the inner side of the busbar.
[0022] The following are the descriptions of the reference numerals:
[0023] 11: first bus bar;
[0024] 12: first electrode finger;
[0025] 13: First virtual finger;
[0026] 14: first trace;
[0027] 21: Second bus bar;
[0028] 22: second electrode finger;
[0029] 23: The second virtual finger;
[0030] 24: second trace;
[0031] 31: reflector;
[0032] 50: symmetry center;
[0033] 51-54: trace points;
[0034] 100: silicon substrate;
[0035] 200, polysilicon layer;
[0036] 300: silicon dioxide layer;
[0037] 400: piezoelectric layer;
[0038] 500: interdigitated electrodes;
[0039] 600: passivation layer;
[0040] 1-S to 6-S: the first segment to the sixth segment. DETAILED DESCRIPTION
[0041] The technical solution of the present disclosure is further specifically described below through examples and in conjunction with the accompanying drawings. In the specification, the same or similar figure numbers indicate the same or similar parts. The following description of the embodiments of the present disclosure with reference to the accompanying drawings is intended to explain the overall inventive concept of the present disclosure and should not be understood as a limitation on the present disclosure. Some embodiments of the invention, not all embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field are within the scope of protection of the present disclosure.
[0042] like Figure 1 As shown, the distance between the ends of the adjacent first electrode fingers 12 and the second electrode fingers 22 in the direction perpendicular to the propagation direction of the surface acoustic wave (eg Figure 1 The pore size is defined as the pore size or the pore size of the finger. Figure 1 In the surface acoustic wave transducer shown, the aperture size and lateral position (ie, the position in the direction perpendicular to the propagation direction of the surface acoustic wave or along the extension direction of the electrode fingers) are constant, which may cause the problem of lateral energy leakage of the acoustic wave.
[0043] In the present disclosure, the interdigitated electrode includes at least one envelope unit, at least one of the first envelope line and the second envelope line defined by the envelope unit is a step trace, and for the bus bar near the step trace in the first bus bar and the second bus bar, the position change of at least a portion of the edge of the side edge (i.e., the inner edge mentioned later) of the electrode finger in the length direction of the electrode finger corresponds to the position change of the envelope line near the at least a portion of the edge in the length direction of the electrode finger. The correspondence here means that the trends of the position changes of the two correspond. Through this structure, the deterioration of the filter performance caused by the lateral mode can be effectively suppressed, thereby making the filter passband flatter.
[0044] For example, the trend of the position change of the two can be represented by the distance relative to the outer edge of the bus bar, specifically, the distance from the side edge of the bus bar corresponding to the side edge where the electrode finger is set is closer or farther away. Figure 3 Middle: The second trace 24 and the first bus bar 11 Figure 3 The distance between the upper edge (ie, the outer edge corresponding to the inner edge) of the first bus bar 11 decreases from the 1-S region to the 3-S region. Figure 3 The distance from the lower edge (ie, inner edge) to the upper edge of the second trace 24 is also reduced from the 1-S region to the 3-S region; Figure 3 The distance between the upper edge of the first bus bar 11 increases from the 4-S region to the 6-S region. Figure 3 The distance from the lower edge to the upper edge of the circuit also increases from the 4-S region to the 6-S region; the distance between the first trace 14 and the second bus bar 21 Figure 3 The distance between the lower edge of the second bus bar 21 and the lower edge of the second bus bar 21 decreases from the 1-S region to the 3-S region. Accordingly, the distance between the lower edge of the second bus bar 21 and the outer edge of the second bus bar 21 decreases from the 1-S region to the 3-S region. Figure 3 The distance from the upper edge (inner edge of the second bus bar 21) to the lower edge (outer edge of the second bus bar 21) in the circuit is also reduced from the 1-S region to the 3-S region; Figure 3 The distance between the lower edge of the bus bar 21 (the outer edge of the second bus bar 21) increases from the 4-S region to the 6-S region. Accordingly, the distance between the lower edge of the bus bar 21 and the outer edge of the second bus bar 21 increases from the 4-S region to the 6-S region. Figure 3 The distance from the upper edge (the inner edge of the second bus bar 21) to the lower edge (the outer edge of the second bus bar 21) also increases from the 4-S region to the 6-S region. Figure 8-Figure 13 There is a similar corresponding relationship of position changes in , which will not be repeated here.
[0045] It should be pointed out that in the present disclosure, as long as at least one envelope line includes a step trace, and the position change of at least a portion of the side edge of the electrode finger in the length direction of the electrode finger corresponds to the position change of the envelope line close to the at least a portion of the edge in the length direction of the electrode finger, it is within the protection scope of the present disclosure.
[0046] More specifically, in the present disclosure, it is not required that the envelope be a step trace as a whole but may include a step trace. For a bus bar close to the step trace, the position change of at least a portion of the side edges of the electrode fingers provided thereon in the direction of the length of the electrode fingers corresponds to the position change of the step trace close to the at least a portion of the edges in the direction of the length of the electrode fingers. In a further embodiment, the at least one side edge includes at least two segment edges corresponding to at least two step segments of the step trace, and the position change of the at least two segment edges in the direction of the length of the electrode fingers corresponds to the position change of the at least two step segments of the step trace in the direction of the length of the electrode fingers. The above structure can effectively suppress the performance deterioration caused by the lateral mode on the basis of maintaining the trace step, and can obtain a larger quality factor.
[0047] The technical solution of the present disclosure is exemplarily described below with reference to the accompanying drawings.
[0048] Figure 2 FIG. 1 is a schematic top view of a surface acoustic wave transducer according to an exemplary embodiment of the present disclosure. Figure 4 for Figure 2 Schematic diagram of the cross section of the surface acoustic wave transducer. Figure 4 As shown in FIG. 4 , the surface acoustic wave transducer includes a piezoelectric layer 400 and interdigital electrodes 500. The interdigital electrodes 500 are arranged on the surface of the piezoelectric layer 400. Figure 2As shown, the interdigitated electrode 500 includes a first bus bar 11, a plurality of first electrode fingers 12 connected to the first bus bar 11, a second bus bar 21, and a plurality of second electrode fingers 22 connected to the second bus bar 21. The plurality of first electrode fingers 12 and the plurality of second electrode fingers 22 are arranged in an interlaced manner in the propagation direction of the surface acoustic wave and have overlapping sections. The interdigitated electrode also includes a first virtual finger 13 and a second virtual finger 23. The plurality of first virtual fingers 13 and the plurality of first electrode fingers 12 are alternately connected to the first bus bar 11. The plurality of second virtual fingers 23 and the plurality of second electrode fingers 22 are alternately connected to the second bus bar 21. Each first electrode finger 12 and a corresponding second virtual finger 23 are arranged relative to each other and there is a gap. Each second electrode finger 22 and a corresponding first virtual finger 13 are arranged relative to each other and there is a gap. As known to those skilled in the art, reflectors 31 are also provided on both sides of the interdigitated electrode.
[0049] In an optional embodiment, the thickness of the first bus bar 11 and / or the second bus bar 21 is greater than or equal to 1 micrometer and less than or equal to 6 micrometers. In an optional embodiment, the material of the first bus bar 11 and / or the second bus bar 21 is, for example, aluminum.
[0050] As known to those skilled in the art, Figure 2 In the figure, the horizontal direction is the propagation direction of the surface acoustic wave.
[0051] Figure 3 Shows Figure 2 The trace and symmetry center of the SAW transducer. Figure 2 and Figure 3 As shown, the interdigitated electrode 500 includes an envelope unit. The envelope unit includes a first envelope 14 defined by the ends of a plurality of first electrode fingers 12, and a second envelope 24 defined by the ends of a plurality of second electrode fingers 22. The end of each first electrode finger 12 constitutes a trace point of the first envelope 14, and the end of each second electrode finger 22 constitutes a trace point of the second envelope 24. Figure 3 , two trace points on the first envelope 14, namely, trace point 51 and trace point 52, and two trace points on the second envelope 24, namely, trace point 53 and trace point 54. It is easy to understand that the first envelope 14 and the second envelope 24 also include other trace points.
[0052] like Figure 3 As shown, the first envelope 14 and the second envelope 24 each include a plurality of horizontal segments or step segments (arranged in parallel with the busbars), and there is a gradient between adjacent horizontal segments, so the first envelope 14 and the second envelope 24 are both step traces. Figure 3As shown, when the outer frame of the envelope unit is a rectangle, there is a gradient between adjacent horizontal segments; however, as mentioned later, the outer frame of the envelope unit can also form a parallelogram structure, in which case there is a gradient between adjacent segments parallel to the busbar.
[0053] In this embodiment, both the first envelope 14 and the second envelope 24 are step traces. In other embodiments, although not shown, only one of the first envelope 14 and the second envelope 24 may be a step trace. In other embodiments, although not shown, only a portion of the first envelope 14 or the second envelope 24 may be a step trace.
[0054] In this embodiment, Figure 3 As shown, for the busbars near the step traces in the first busbar 11 and the second busbar 12, the side edges (hereinafter referred to as inner side edges or inner edges) where the electrode fingers are arranged include at least two sections corresponding to at least two horizontal sections of the step traces. Figure 3 The first trace 14 in the figure, the bus bar close to the step trace is the second bus bar 21, and the upper side of the electrode finger has multiple sections corresponding to the horizontal sections of the step trace, which are divided into the first section 1-S, the second section 2-S... the sixth section 6-3. The change of the position of each of the above sections in the length direction of the electrode finger (hereinafter referred to as the lateral position) has a change trend corresponding to the change of the position of the step trace in the length direction of the electrode finger. The trend of the position change of the two can be expressed by the change of the lateral position. For example, from left to right, the first trace 14 first drops and then rises. Correspondingly, the lateral position of the second section 2-S is lower than the lateral position of the first section 1-S as a whole, and the lateral position of the third section 3-S is lower than the lateral position of the second section 2-S as a whole... The lateral position of the sixth section 6-S is higher than the lateral position of the fifth section 5-S as a whole.
[0055] Here, the lateral position of a certain segment is higher (or lower) than the lateral position of another segment as a whole. The lateral position of each point in the segment may be higher (or lower) than the lateral position of any point in the other segment. The mean of the lateral positions of the points in the segment may be higher (or lower) than the mean of the lateral positions of the points in the other segment.
[0056] In an optional embodiment, if Figure 3 As shown, the inner sides of the first bus bar 11 and the second bus bar 12 have a stepped shape corresponding to the step trace, each segment of the inner side is a horizontal segment corresponding to the horizontal segment of the step trace, and the distances from different segments to the corresponding horizontal segments of the step trace are equal.
[0057] In an optional embodiment, if Figure 2 and Figure 3As shown, for the busbars near the step traces in the first busbar 11 and the second busbar 12, the side without electrode fingers is a straight side. In other embodiments, although not shown, the side without electrode fingers can also be other shapes.
[0058] In the present disclosure, the distance between the side of the bus bar where the electrode fingers are provided and the opposite side defines the bus bar width. In an optional embodiment, the minimum bus bar width corresponding to each section is 0.2 times to 4 times the wavelength of the surface acoustic wave transducer, and the maximum bus bar width corresponding to each section is 2.4 times to 8 times the wavelength of the surface acoustic wave transducer.
[0059] In an optional embodiment, if Figure 3 As shown, at least one section of the inner side of the first bus bar 11 and the corresponding section of the inner side of the second bus bar 12 are in a centrally symmetrical relationship relative to the center 50 of the envelope unit. In the present disclosure, the outer frame of the envelope unit is a rectangle, and the center 50 of the rectangle is the center of symmetry in the above-mentioned centrally symmetrical relationship. It should also be pointed out that, although not shown, in the case where the outer frame of the envelope unit of the present disclosure is other parallelograms, the intersection of the two diagonals of the parallelogram is the center of symmetry. In other words, in the present disclosure, the outer frame of the envelope unit can be not only a rectangle, but also a parallelogram other than a rectangle.
[0060] like Figure 3 As shown, all the sections of the inner side of the first bus bar 11 have corresponding central symmetry. In other embodiments, although not shown, some of the multiple sections of the inner side of the first bus bar 11 may have corresponding central symmetry and others may not have corresponding central symmetry.
[0061] In an optional embodiment, if Figure 3 As shown, the trace points on the first envelope 14 and the trace points on the second envelope 24 may have a corresponding central symmetric relationship. Exemplarily, the trace points 51 on the first envelope 14 and the trace points 54 on the second envelope 24 are symmetric about the symmetry center 50, and the trace points 52 on the first envelope 14 and the trace points 53 on the second envelope 24 are symmetric about the symmetry center 50.
[0062] In an optional embodiment, if Figure 3 As shown, on each side of the symmetry center 50, the inner side of the first bus bar 11 or the second bus bar 21 includes the first segment to the third segment adjacent to each other along the propagation direction of the surface acoustic wave, that is, 1-S to 3-S, or 4-S to 6-S in the figure. From the symmetry, it can be seen that the segment 1-S and the segment 6-S have the same structural parameters (such as segment length, bus bar width, etc.), the segment 2-S and the segment 5-S have the same structural parameters, and the segment 3-S and the segment 4-S have the same structural parameters.
[0063] In the above embodiment, the widths of the busbars in adjacent sections vary in steps. For example, from section 1-S to section 3-S, the widths of the first busbar 11 and the second busbar 12 decrease in sequence.
[0064] In an optional embodiment, if Figure 3 As shown, the busbar width in each segment is uniform. In other embodiments, as shown in FIG. Figure 10-13 As shown, there may be variations in bus bar width within each segment.
[0065] In an alternative embodiment, each segment corresponds to a plurality of equal finger apertures, e.g. Figure 2 Each segment corresponds to two finger apertures, and the two finger apertures are equal. Therefore, the end of the real finger on each segment defines a horizontal segment of the step trace. It is easy to understand that the number of fingers on each segment (here refers to the total number of real fingers and virtual fingers on a single bus bar) is 4 or more.
[0066] In an optional embodiment, if Figure 2 As shown, the number of fingers on each segment is equal. The above-mentioned equal number of fingers may be approximately equal. For example, when the number of fingers is large (e.g., 50), a small difference (e.g., 3 or 5) in the number of fingers on each segment is allowed. In an optional embodiment, the number of fingers on each segment is greater than or equal to 10 and less than or equal to 60. In other embodiments, the number of fingers on each segment may also be different.
[0067] like Figure 3 As shown, in the propagation direction of the surface acoustic wave, the finger apertures corresponding to the multiple segments on each side of the symmetry center 50 change monotonically from the symmetry center 50 to the outside. Figure 3 In the embodiment, the monotonous change is a sequential decrease. For example, from the symmetric center 50 to the left, the finger apertures corresponding to the segments 3-S, 2-S, and 1-S decrease in sequence, and from the symmetric center 50 to the right, the finger apertures corresponding to the segments 4-S, 5-S, and 6-S decrease in sequence. In other embodiments, although not shown, the monotonous change may be a sequential increase.
[0068] In an optional embodiment, if Figure 3 As shown, the lengths of the virtual fingers on each bus bar are the same, and the change in the aperture is achieved by changing the width of the bus bar and the length of the real fingers.
[0069] In an optional embodiment, if Figure 2As shown, the finger apertures corresponding to each section are located at the center of the envelope unit in the direction perpendicular to the propagation direction of the surface acoustic wave, that is, the finger apertures of each section are centered horizontally. At this time, the outer frame of the envelope unit is a rectangle. As can be understood, when the outer frame of the envelope unit is a parallelogram, the line passing through the symmetry center and parallel to the bus bar is the median line of the finger apertures of each area.
[0070] In an optional embodiment, if Figure 2 and Figure 3 As shown, the variation gradients of the finger apertures between adjacent sections are all equal. In other embodiments, although not shown, the variation gradients of the finger apertures between adjacent sections may also be different.
[0071] In the present disclosure, the number of segments on each side of the symmetry center 50 can be determined according to the specific situation, and can be 4 or 5, etc., in addition to 3. It is easy to understand that the number of segments on each side of the symmetry axis is at least 2.
[0072] In each embodiment of the present disclosure, dummy fingers (i.e., dummy electrodes) are provided, so that: the first bus bar 11 is provided with a first dummy finger 13 spaced opposite to the second electrode finger 22 to form a first gap, and the second bus bar 21 is provided with a second dummy finger 23 spaced opposite to the first electrode finger 12 to form a second gap. However, the present disclosure is not limited thereto, and dummy fingers may not be provided.
[0073] In an optional embodiment, if Figure 3 As shown, the lengths of the first virtual fingers 13 and / or the second virtual fingers 23 in each section are the same. The lengths of the first virtual fingers 13 and / or the second virtual fingers 23 in each section in the propagation direction of the surface acoustic wave are the same.
[0074] In an optional embodiment, if Figure 3 As shown, the first gap and / or the second gap in each section are equal, and the first gap and / or the second gap corresponding to each section are equal.
[0075] Figure 5 for Figure 2 Schematic diagram of the interdigitated electrode portion of a surface acoustic wave transducer showing the various dimensions.
[0076] like Figure 5As shown, W1 is the average value of the finger apertures corresponding to multiple segments. When the number of segments on each side of the symmetry axis is 3 and the change gradient of the finger apertures between adjacent segments is equal, W1 is the finger aperture of 2-S and 4-S, and W2 is the change gradient of the finger apertures between adjacent segments. In an optional embodiment, W1 is 10 to 35 times the wavelength of the surface acoustic wave transducer, and W2 is 0.025 to 0.15 times W1, that is, W1 = 10 to 35λ, W2 = 0.025 to 0.15W1.
[0077] like Figure 5 As shown, Gap is the size of the first gap and / or the second gap, and is also the distance between the real finger and the corresponding virtual finger. In an optional embodiment, Gap is 0.02 to 0.15 times the wavelength of the surface acoustic wave transducer, that is, Gap = 0.02 to 0.15λ.
[0078] like Figure 5 As shown, L1 is the busbar width in the first section and the sixth section, L2 is the busbar width in the second section and the fifth section, and L3 is the busbar width in the third section and the fourth section. In an optional embodiment, L1 is 2.4 to 6.4 times the wavelength of the surface acoustic wave transducer, that is, L1 = 2.4 to 6.4λ, L2 is 0.9 to 4.9 times the wavelength of the surface acoustic wave transducer, that is, L2 = 0.9 to 4.9λ, and L3 is 0.2 to 3.4 times the wavelength of the surface acoustic wave transducer, that is, L3 = 0.2 to 3.4λ.
[0079] like Figure 5 As shown, L4 is the length of the virtual finger in each section. In an optional embodiment, L4 is 0.02 to 0.3 times the wavelength of the surface acoustic wave transducer, that is, L4 = 0.02 to 0.3λ.
[0080] Figure 6 The comparison chart of the test results shows the Figure 1 and Figure 2 The curve of the real part of the admittance of the surface acoustic wave transducer changing with frequency. Figure 6 In the figure, curve 1 corresponds to Figure 1 The curve of the real part of the admittance of the surface acoustic wave transducer changing with frequency. Curve 2 corresponds to Figure 2 The curve of the real part of the admittance of the surface acoustic wave transducer changing with frequency. Figure 6 It can be seen that in each frequency band, Figure 2 The curve of the real part of the admittance of the surface acoustic wave transducer changing with frequency is compared with Figure 1 The curves of the real part of the admittance of the surface acoustic wave transducer changing with frequency are smoother, indicating that the surface acoustic wave transducer disclosed in the present invention has a better suppression effect on the transverse mode.
[0081] Figure 7 is a comparison chart of the test results, which shows Figure 1 and Figure 2 The quality factor of the surface acoustic wave transducer varies with frequency. Figure 7 In the figure, curve 3 corresponds to Figure 1 The quality factor of the surface acoustic wave transducer varies with frequency. Curve 4 corresponds to Figure 2 The quality factor of the surface acoustic wave transducer varies with frequency. Figure 7 It can be seen that Figure 2 The quality factor curve of the surface acoustic wave transducer is generally higher than that of Figure 1 The curve of the quality factor of the surface acoustic wave transducer changing with frequency shows that the surface acoustic wave transducer in the present disclosure can obtain a higher quality factor.
[0082] Figure 8 and Fig. 9 for Figure 2 Variations of the surface acoustic wave transducer. Figure 2 In the embodiment, the interdigitated electrode 500 includes an envelope unit, and in Figure 8 and Fig. 9 In the example, the interdigitated electrodes are Figure 2 The envelope units in form a periodic structure. Figure 2 The interdigitated electrodes in can also be called a single-period structure.
[0083] like Figure 8 As shown in the figure, the interdigital electrode includes two envelope units, which is a double-period structure. The double-period structure is evolved on the basis of the envelope unit, so the structural design parameters are consistent with the single-period design. When the design frequency is low or the number of fingers is relatively small, the double period can be used as a basic unit for filter design. This structure can effectively suppress the lateral mode and improve the filter performance.
[0084] like Fig. 9 As shown in the figure, the interdigital electrode includes three envelope units, which is a three-periodic structure. The three-periodic structure is evolved from the single-periodic structure, so the structural design parameters are the same as the single-periodic design. When designing high frequencies or when the number of fingers is relatively large, the three-period can be used as a basic unit for filter design. This structure can effectively suppress the lateral mode and improve the filter performance.
[0085] exist Figure 8 and Fig. 9In the illustrated embodiment, the interdigitated electrodes include a periodic structure extending with an envelope unit as a period in the propagation direction of the surface acoustic wave. In the propagation direction of the surface acoustic wave, the length of the periodic structure is an integer multiple of the length of the single-period structure. In addition, although not shown, it can also be a non-integer multiple, such as 1.5 times, that is, in the propagation direction of the surface acoustic wave, the length of the periodic structure is a non-integer multiple of the length of the envelope unit. The non-integer multiple here can be reflected in that the single envelope unit at the rear in the propagation direction of the surface acoustic wave includes a part but not all of the single envelope unit at the front in the propagation direction of the surface acoustic wave, or can be reflected in that the single envelope unit at the front in the propagation direction of the surface acoustic wave includes a part but not all of the single envelope unit at the rear in the propagation direction of the surface acoustic wave.
[0086] Although not shown, an envelope unit may be arranged adjacent to another envelope unit or exist adjacent to another envelope unit in the interdigital electrodes of the surface acoustic wave transducer. For example, the length of the single envelope unit at the rear in the propagation direction of the surface acoustic wave is different from the length of the single envelope unit at the front in the propagation direction of the surface acoustic wave. The envelope unit here may be a periodic envelope unit or a non-periodic envelope unit.
[0087] In an alternative implementation, if Figure 4 As shown, the surface acoustic wave transducer also includes a polysilicon layer 200, a silicon dioxide layer 300 and a passivation layer 600. The polysilicon layer 200 is disposed on the silicon substrate 100, the silicon dioxide layer 300 is disposed on the polysilicon layer 200, and the piezoelectric layer 400 is disposed on the silicon dioxide layer 300. The passivation layer 600 covers the interdigital electrodes 500 to play a protective role. The polysilicon layer 200 acts as an energy trap layer, which is conducive to further improving the Q value of the surface acoustic wave transducer.
[0088] In an optional embodiment, the silicon substrate 100 may be made of high-resistance silicon. Optionally, the resistivity of the silicon substrate 100 is greater than 2000 Ω-cm. Further, the resistivity of the silicon substrate 100 is greater than 10000 Ω-cm.
[0089] It should be pointed out that in the present disclosure, for numerical ranges, unless explicitly excluded, the endpoint values are included. In addition, it may also be the midpoint value, one-third value, or two-thirds value of the numerical range.
[0090] Figure 10-13 for Figure 2 Variations of the SAW transducer showing different shapes of the inner side of the bus bar.
[0091] like Fig.10 As shown, on the same bus bar, all sections located on the same side of the symmetry center in the propagation direction of the surface acoustic wave are straight lines, connected at the ends and have the same slope, thus forming a straight line as a whole.
[0092] like Fig.11 As shown, on the same busbar, all the segments on the same side of the symmetry center in the propagation direction of the surface acoustic wave are straight lines and connected at the ends. Among them, the segments adjacent to the symmetry center (i.e., the middle segments, such as segment 3-S and segment 4-S) are horizontal lines, and the other segments are inclined lines.
[0093] like Fig.12 As shown in the figure, on the same busbar, all the sections on the same side of the symmetry center in the propagation direction of the surface acoustic wave are straight lines, connected at the end but with different slopes. Fig.12 In the figure, the slope values of the straight lines gradually increase from the center of symmetry to the outside. In addition, there can be other changes, such as gradually decreasing, increasing first and then decreasing, decreasing first and then increasing, increasing first and then unchanged, etc.
[0094] like Fig.12 As shown, on the same bus bar, each section located on the same side of the symmetry center in the propagation direction of the surface acoustic wave can be a curve, and the curve can be a convex curve or a concave curve.
[0095] In other embodiments, although not shown, on the same bus bar, sections located on the same side of the symmetry center in the propagation direction of the surface acoustic wave may include both straight lines and curved lines.
[0096] In the embodiments of the present disclosure, the adjacent sections may be continuous, discontinuous or stepped. In the case of continuity, the connection may be smooth or not smooth.
[0097] In the embodiment of the present disclosure, each section can be further divided into a plurality of sub-sections. Each sub-section can be a straight line or a curve, and adjacent sub-sections can be continuous or discontinuous.
[0098] In the present disclosure, at least a portion of the edge of the side edge of the bus bar where the electrode fingers are provided (whose position changes in the length direction of the electrode fingers) can be a straight line segment, an arc segment, or a combination of straight line segments, a combination of arc segments, or a combination of straight line segments and arc segments.
[0099] It should be pointed out that in the present disclosure, the bus bar may include a rectangular strip portion and a position changing portion where electrode fingers are set. These two portions may be integrally formed or may be formed one after another. The materials of the two portions may be the same or different, all of which are within the protection scope of the present disclosure.
[0100] It should also be pointed out that in the present disclosure, the so-called "position change trend" means that in a section along the direction of sound wave propagation or substantially along the direction of sound wave propagation, the position of at least a portion of the side edge of the bus bar where the electrode fingers are arranged in the length direction of the electrode fingers tends to be close to or away from the outer edge of the bus bar. The edge of the bus bar where the electrode fingers are arranged is the inner edge of the bus bar, and the edge of the bus bar opposite to the inner edge is the outer edge.
[0101] The present disclosure also provides a device, comprising the aforementioned surface acoustic wave transducer. The device may be a filter or other device or apparatus using the aforementioned surface acoustic wave transducer.
[0102] Based on the above, the present disclosure proposes the following technical solutions:
[0103] 1. A surface acoustic wave transducer, comprising:
[0104] Piezoelectric layer;
[0105] The interdigitated electrodes are arranged on the surface of the piezoelectric layer, and include: a first bus bar and a plurality of first electrode fingers connected to the first bus bar, a second bus bar and a plurality of second electrode fingers connected to the second bus bar,
[0106] in:
[0107] The interdigitated electrode comprises at least one envelope unit, wherein the envelope unit has a first envelope defined by ends of the plurality of first electrode fingers and / or a second envelope defined by ends of the plurality of second electrode fingers, and at least a portion of the first envelope and / or the second envelope is a step trace;
[0108] For the bus bar in the first bus bar and / or the second bus bar that is close to the step trace, there is a corresponding trend in the position change of at least a portion of the edge of the side edge of the electrode finger in the length direction of the electrode finger and a corresponding trend in the position change of the envelope line close to at least a portion of the edge in the length direction of the electrode finger.
[0109] 2. The surface acoustic wave transducer according to item 1, wherein:
[0110] For the bus bar in the first bus bar and / or the second bus bar that is close to the step trace, there is a position change trend of at least a portion of the edge of the side edge of the electrode finger provided with the electrode finger in the length direction of the electrode finger, which corresponds to the position change trend of the step trace close to the at least a portion of the edge in the length direction of the electrode finger.
[0111] 3. The surface acoustic wave transducer according to 2, wherein:
[0112] The at least one side edge includes at least two segment edges corresponding to the at least two step segments of the step trace, and the position change trend of the at least two segment edges in the length direction of the electrode finger corresponds to the position change trend of the at least two step segments of the step trace in the length direction of the electrode finger.
[0113] 4. The surface acoustic wave transducer according to 3, wherein:
[0114] The at least two segment edges form a stepped shape corresponding to the at least two stepped segments of the stepped trace.
[0115] 5. The surface acoustic wave transducer according to 3, wherein:
[0116] At least one of the at least two segment edges is a straight line edge.
[0117] 6. The surface acoustic wave transducer according to 5, wherein:
[0118] Among the at least two segment edges, different segment edges located on the same side of the center of the envelope unit in the propagation direction of the surface acoustic wave have different slopes.
[0119] 7. The surface acoustic wave transducer according to 5, wherein:
[0120] The middle segment edge of the at least two segment edges is a horizontal edge, and the other segment edges are inclined edges.
[0121] 8. The surface acoustic wave transducer according to 3, wherein:
[0122] At least one of the at least two segment edges is a curved edge.
[0123] 9. A surface acoustic wave transducer according to any one of 3 to 8, wherein:
[0124] The first bus bar has a first side with first electrode fingers, the second bus bar has a second side with second electrode fingers, and at least one segment edge of the first side is symmetrical with a corresponding segment edge of the second side about a same point.
[0125] 10. The surface acoustic wave transducer according to 9, wherein:
[0126] All segment edges of the first side and corresponding segment edges of the second side are centrally symmetrical about a same point.
[0127] 11. The surface acoustic wave transducer according to 3, wherein:
[0128] The distance between the side of the bus bar where the electrode fingers are provided and the opposite side in the length direction of the electrode fingers defines the bus bar width, the minimum bus bar width corresponding to the at least two segment edges is 0.2 times to 4 times the wavelength of the surface acoustic wave transducer, and the maximum bus bar width corresponding to the at least two segment edges is 2.4 times to 8 times the wavelength of the surface acoustic wave transducer.
[0129] 12. The surface acoustic wave transducer according to 3, wherein:
[0130] The lengths of the first virtual fingers and / or the second virtual fingers in each segment edge of the at least two segment edges are the same.
[0131] 13. The surface acoustic wave transducer according to 12, wherein:
[0132] The lengths of the first virtual fingers and / or the second virtual fingers corresponding to the at least two segment edges in the propagation direction of the surface acoustic wave are the same.
[0133] 14. The surface acoustic wave transducer according to 3, wherein:
[0134] The length of the first virtual finger and / or the second virtual finger is 0.02 times to 0.3 times the wavelength of the surface acoustic wave transducer.
[0135] 15. The surface acoustic wave transducer according to 3, wherein:
[0136] The first gap and / or the second gap is / are 0.02 times to 0.15 times the wavelength of the surface acoustic wave transducer.
[0137] 16. The surface acoustic wave transducer according to 3, wherein:
[0138] The number of fingers corresponding to each segment edge of the at least two segment edges is equal.
[0139] 17. The surface acoustic wave transducer according to 3, wherein:
[0140] In the propagation direction of the surface acoustic wave, the finger apertures corresponding to the edges of the at least two segments change monotonically from the center of the envelope unit to the outside.
[0141] 18. The surface acoustic wave transducer according to 17, wherein:
[0142] In the propagation direction of the surface acoustic wave, the finger apertures corresponding to the edges of the at least two segments decrease sequentially from the center of the envelope unit to the outside.
[0143] 19. The surface acoustic wave transducer according to 9, wherein:
[0144] On each side of the symmetry center corresponding to the central symmetry, the first side includes a first segment edge to a third segment edge adjacent to each other in sequence, and the third segment edge is adjacent to the symmetry center.
[0145] 20. The surface acoustic wave transducer according to 19, wherein:
[0146] The distance between the side of the bus bar where the electrode fingers are provided and the opposite side defines the bus bar width. The bus bar width at the edge of the first section is 2.4 to 6.4 times the wavelength of the surface acoustic wave transducer, the bus bar width within the edge of the second section is 0.9 to 4.9 times the wavelength of the surface acoustic wave transducer, and the bus bar width within the edge of the third section is 0.2 to 3.4 times the wavelength of the surface acoustic wave transducer.
[0147] 21. The surface acoustic wave transducer according to 9, wherein:
[0148] On each side of the symmetry center corresponding to the central symmetry, the first side includes at least three segment edges adjacent to each other in sequence;
[0149] The variation gradients of the finger apertures between the edges of adjacent segments in the at least three segment edges are all equal.
[0150] 22. The surface acoustic wave transducer according to 21, wherein:
[0151] The average value of the finger apertures corresponding to the edges of the at least three segments is 10 to 35 times the wavelength of the surface acoustic wave transducer.
[0152] 23. The surface acoustic wave transducer according to 21, wherein:
[0153] The variation gradient of the finger apertures between adjacent segment edges among the at least three segment edges is 0.025 times to 0.15 times the average value of the finger apertures corresponding to the at least three segment edges.
[0154] 24. The surface acoustic wave transducer according to 3, wherein:
[0155] The number of fingers in each of the at least two segment edges is greater than or equal to 10 and less than or equal to 60.
[0156] 25. The surface acoustic wave transducer according to item 1, wherein:
[0157] The interdigital electrodes include a periodic structure extending with the envelope unit as a period in the propagation direction of the surface acoustic wave, and the periodic structure includes at least two envelope units arranged in sequence and adjacent to each other in the propagation direction of the surface acoustic wave.
[0158] 26. The surface acoustic wave transducer according to item 1, wherein:
[0159] The interdigital electrodes include a periodic structure extending with the envelope units as a period in the propagation direction of the surface acoustic wave, and the periodic structure includes at least three envelope units arranged adjacent to each other in the propagation direction of the surface acoustic wave.
[0160] 27. The surface acoustic wave transducer according to item 1, wherein:
[0161] The interdigitated electrodes include a periodic structure extending with the envelope unit as a period in the propagation direction of the surface acoustic wave, and in the propagation direction of the surface acoustic wave, the length of the periodic structure is a non-integer multiple of the length of the envelope unit; or
[0162] The interdigital electrode includes two different envelope units arranged adjacent to each other.
[0163] 28. The surface acoustic wave transducer according to item 1, wherein:
[0164] A thickness of the first bus bar and / or the second bus bar is greater than or equal to 1 micrometer and less than or equal to 6 micrometers.
[0165] 29. The surface acoustic wave transducer according to item 1, wherein:
[0166] For the bus bar in the first bus bar and / or the second bus bar close to the step trace, at least a portion of the edge of the side edge where the electrode finger is provided is a straight line segment, or an arc segment, or a combination of straight line segments, or a combination of arc segments, or a combination of straight line segments and arc segments.
[0167] 30. A device comprising the surface acoustic wave transducer according to any one of 1-29.
[0168] While embodiments of the present disclosure have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A surface acoustic wave transducer, comprising: Piezoelectric layer; The interdigitated electrodes are arranged on the surface of the piezoelectric layer, and include: a first bus bar and a plurality of first electrode fingers connected to the first bus bar, a second bus bar and a plurality of second electrode fingers connected to the second bus bar, in: The interdigitated electrode comprises at least one envelope unit, wherein the envelope unit has a first envelope defined by ends of the plurality of first electrode fingers and / or a second envelope defined by ends of the plurality of second electrode fingers, and at least a portion of the first envelope and / or the second envelope is a step trace; For the bus bar in the first bus bar and / or the second bus bar that is close to the step trace, there is a corresponding trend in the position change of at least a portion of the edge of the side edge of the electrode finger in the length direction of the electrode finger and a corresponding trend in the position change of the envelope line close to at least a portion of the edge in the length direction of the electrode finger.
2. The surface acoustic wave transducer according to claim 1, wherein: For the bus bar in the first bus bar and / or the second bus bar that is close to the step trace, there is a position change trend of at least a portion of the edge of the side edge of the electrode finger provided with the electrode finger in the length direction of the electrode finger, which corresponds to the position change trend of the step trace close to the at least a portion of the edge in the length direction of the electrode finger.
3. The surface acoustic wave transducer according to claim 2, wherein: The at least one side edge includes at least two segment edges corresponding to the at least two step segments of the step trace, and the position change trend of the at least two segment edges in the length direction of the electrode finger corresponds to the position change trend of the at least two step segments of the step trace in the length direction of the electrode finger.
4. The surface acoustic wave transducer according to claim 3, wherein: The at least two segment edges form a stepped shape corresponding to the at least two stepped segments of the stepped trace.
5. The surface acoustic wave transducer according to claim 3, wherein: At least one of the at least two segment edges is a straight line edge.
6. The surface acoustic wave transducer according to claim 5, wherein: Among the at least two segment edges, different segment edges located on the same side of the center of the envelope unit in the propagation direction of the surface acoustic wave have different slopes.
7. The surface acoustic wave transducer according to claim 5, wherein: The middle segment edge of the at least two segment edges is a horizontal edge, and the other segment edges are inclined edges.
8. The surface acoustic wave transducer according to claim 3, wherein: At least one of the at least two segment edges is a curved edge.
9. The surface acoustic wave transducer according to any one of claims 3 to 8, wherein: The first bus bar has a first side with first electrode fingers, the second bus bar has a second side with second electrode fingers, and at least one segment edge of the first side is symmetrical with a corresponding segment edge of the second side about a same point.
10. The surface acoustic wave transducer according to claim 9, wherein: All segment edges of the first side and corresponding segment edges of the second side are centrally symmetrical about a same point.
11. The surface acoustic wave transducer according to claim 3, wherein: The distance between the side of the bus bar where the electrode fingers are provided and the opposite side in the length direction of the electrode fingers defines the bus bar width, the minimum bus bar width corresponding to the at least two segment edges is 0.2 times to 4 times the wavelength of the surface acoustic wave transducer, and the maximum bus bar width corresponding to the at least two segment edges is 2.4 times to 8 times the wavelength of the surface acoustic wave transducer.
12. The surface acoustic wave transducer according to claim 3, wherein: The lengths of the first virtual fingers and / or the second virtual fingers in each segment edge of the at least two segment edges are the same.
13. The surface acoustic wave transducer according to claim 12, wherein: The lengths of the first virtual fingers and / or the second virtual fingers corresponding to the at least two segment edges in the propagation direction of the surface acoustic wave are the same.
14. The surface acoustic wave transducer according to claim 3, wherein: The length of the first virtual finger and / or the second virtual finger is 0.02 times to 0.3 times the wavelength of the surface acoustic wave transducer.
15. The surface acoustic wave transducer according to claim 3, wherein: The first gap and / or the second gap is / are 0.02 times to 0.15 times the wavelength of the surface acoustic wave transducer.
16. The surface acoustic wave transducer according to claim 3, wherein: The number of fingers corresponding to each segment edge of the at least two segment edges is equal.
17. The surface acoustic wave transducer according to claim 3, wherein: In the propagation direction of the surface acoustic wave, the finger apertures corresponding to the edges of the at least two segments change monotonically from the center of the envelope unit to the outside.
18. The surface acoustic wave transducer according to claim 17, wherein: In the propagation direction of the surface acoustic wave, the finger apertures corresponding to the edges of the at least two segments decrease sequentially from the center of the envelope unit to the outside.
19. The surface acoustic wave transducer according to claim 9, wherein: On each side of the symmetry center corresponding to the central symmetry, the first side includes a first segment edge to a third segment edge adjacent to each other in sequence, and the third segment edge is adjacent to the symmetry center.
20. The surface acoustic wave transducer according to claim 19, wherein: The distance between the side of the bus bar where the electrode fingers are provided and the opposite side defines the bus bar width. The bus bar width at the edge of the first section is 2.4 to 6.4 times the wavelength of the surface acoustic wave transducer, the bus bar width within the edge of the second section is 0.9 to 4.9 times the wavelength of the surface acoustic wave transducer, and the bus bar width within the edge of the third section is 0.2 to 3.4 times the wavelength of the surface acoustic wave transducer.
21. The surface acoustic wave transducer according to claim 9, wherein: On each side of the symmetry center corresponding to the central symmetry, the first side includes at least three segment edges adjacent to each other in sequence; The variation gradients of the finger apertures between the edges of adjacent segments in the at least three segment edges are all equal.
22. The surface acoustic wave transducer according to claim 21, wherein: The average value of the finger apertures corresponding to the edges of the at least three segments is 10 to 35 times the wavelength of the surface acoustic wave transducer.
23. The surface acoustic wave transducer according to claim 21, wherein: The variation gradient of the finger apertures between adjacent segment edges among the at least three segment edges is 0.025 times to 0.15 times the average value of the finger apertures corresponding to the at least three segment edges.
24. The surface acoustic wave transducer according to claim 3, wherein: The number of fingers in each of the at least two segment edges is greater than or equal to 10 and less than or equal to 60.
25. The surface acoustic wave transducer according to claim 1, wherein: The interdigital electrodes include a periodic structure extending with the envelope unit as a period in the propagation direction of the surface acoustic wave, and the periodic structure includes at least two envelope units arranged in sequence and adjacent to each other in the propagation direction of the surface acoustic wave.
26. The surface acoustic wave transducer according to claim 1, wherein: The interdigital electrodes include a periodic structure extending with the envelope units as a period in the propagation direction of the surface acoustic wave, and the periodic structure includes at least three envelope units arranged adjacent to each other in the propagation direction of the surface acoustic wave.
27. The surface acoustic wave transducer according to claim 1, wherein: The interdigitated electrodes include a periodic structure extending with the envelope unit as a period in the propagation direction of the surface acoustic wave, and in the propagation direction of the surface acoustic wave, the length of the periodic structure is a non-integer multiple of the length of the envelope unit; or The interdigital electrode includes two different envelope units arranged adjacent to each other.
28. The surface acoustic wave transducer according to claim 1, wherein: A thickness of the first bus bar and / or the second bus bar is greater than or equal to 1 micrometer and less than or equal to 6 micrometers.
29. The surface acoustic wave transducer according to claim 1, wherein: For the bus bar in the first bus bar and / or the second bus bar close to the step trace, at least a portion of the edge of the side edge where the electrode finger is provided is a straight line segment, or an arc segment, or a combination of straight line segments, or a combination of arc segments, or a combination of straight line segments and arc segments.
30. A device comprising a surface acoustic wave transducer according to any one of claims 1 to 29.