Bulk acoustic wave resonator, method of manufacturing the same, filter, and multiplexer

Abstract

The embodiment of the present disclosure provides a bulk acoustic resonator, a manufacturing method thereof, a filter and a multiplexer. The bulk acoustic resonator comprises a substrate; a reflection structure located on a surface of the substrate, wherein a cross section of the reflection structure is perpendicular to the surface of the substrate, the cross section comprises an opposite bottom edge and a top edge, and two side edges connecting the bottom edge and the top edge, the bottom edge is relatively close to the substrate, each side edge comprises at least two first curves, the at least two first curves are not parallel, and an angle between a tangent line of each point on each first curve and a plane where the bottom edge is located satisfies: greater than 0° and less than or equal to 45°; and a first electrode layer, a piezoelectric layer and a second electrode layer which are sequentially and layerwisely arranged on the reflection structure.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to the field of semiconductor, and particularly to a bulk acoustic wave resonator, a method for manufacturing the same, a filter and a multiplexer. BACKGROUND

[0002] With the rapid growth of wireless communication demand, modern wireless communication technology promotes the development of high-frequency components, giving birth to higher frequency communication applications, larger bandwidth, faster data signal transmission. The bulk acoustic wave resonator has the advantages of small size, light weight, low insertion loss, wide frequency band and high quality factor, and its preparation process is compatible with CMOS, which well meets the development needs of wireless communication, and has broad application prospects in wireless communication systems. SUMMARY

[0003] Embodiments of the present disclosure provide a bulk acoustic wave resonator, a method for manufacturing the same, a filter and a multiplexer.

[0004] According to a first aspect of the present disclosure, a bulk acoustic wave resonator is provided, comprising:

[0005] a substrate;

[0006] a reflection structure located on a surface of the substrate, wherein a cross section of the reflection structure perpendicular to the surface of the substrate comprises an opposite bottom edge and top edge, and two side edges connecting the bottom edge and the top edge, the bottom edge is relatively close to the substrate, each of the side edges comprises at least two first curves, the at least two first curves are not parallel, and the tangent of each point on each of the first curves and the plane on which the bottom edge lies satisfies: greater than 0° and less than or equal to 45°; and

[0007] a first electrode layer, a piezoelectric layer and a second electrode layer are sequentially stacked on the reflection structure.

[0008] In some embodiments, the at least two first curves are all line segments; or

[0009] the at least two first curves are all arc lines; or

[0010] of the at least two first curves, at least one of the first curves is a line segment, and the other first curves are arc lines.

[0011] In some embodiments, the first curve comprises a line segment, and the angle between the line segment and the plane on which the bottom edge lies satisfies: greater than or equal to 5° and less than or equal to 45°.

[0012] In some embodiments, the angle between the line segment connected with the bottom edge and the bottom edge satisfies: greater than or equal to 10° and less than or equal to 25°.

[0013] In some embodiments, the angle between the line segment connected with the top edge and the plane where the bottom edge lies satisfies: greater than or equal to 10°, and less than or equal to 25°.

[0014] In some embodiments, the first curve includes an arc, and the angle between the tangent of each point on the arc and the plane where the bottom edge lies satisfies: greater than or equal to 5°, and less than or equal to 45°.

[0015] In some embodiments, the arc includes a concave curve concaved to the substrate, or a convex curve protruding from the substrate.

[0016] In some embodiments, the angle between the tangent of each point on the arc connected with the bottom edge and the plane where the bottom edge lies satisfies: greater than or equal to 10°, and less than or equal to 25°.

[0017] In some embodiments, in two adjacent segments of the first curve, the angle between the tangent of each point on the first curve relatively close to the bottom edge and the plane where the bottom edge lies is greater than the angle between the tangent of each point on the first curve relatively close to the top edge and the plane where the bottom edge lies; along the direction from the bottom edge to the top edge, the length of the projection of the at least two segments of the first curve on the plane where the substrate lies gradually increases; or,

[0018] In some embodiments, in two adjacent segments of the first curve, the angle between the tangent of each point on the first curve relatively close to the bottom edge and the plane where the bottom edge lies is less than the angle between the tangent of each point on the first curve relatively close to the top edge and the plane where the bottom edge lies; along the direction from the bottom edge to the top edge, the length of the projection of the at least two segments of the first curve on the plane where the substrate lies gradually decreases.

[0019] In some embodiments, the side edge further includes:

[0020] a second curve, the second curve being parallel to the bottom edge, and the second curve being located between two adjacent segments of the first curve.

[0021] In some embodiments, the reflective structure includes a cavity or a Bragg reflection layer.

[0022] In some embodiments, the reflective structure includes first reflective gratings and second reflective gratings alternately stacked, wherein the first reflective gratings correspond to the side edge including first sub-curves, and the second reflective gratings correspond to the side edge including second sub-curves, and the first sub-curves and the second sub-curves are not parallel.

[0023] According to a second aspect of the present disclosure, a filter is provided, including one or more bulk acoustic wave resonators as described in the first aspect of the present disclosure.

[0024] According to a third aspect of the present disclosure, a multiplexer is provided, comprising one or more filters according to the second aspect of the present disclosure.

[0025] According to a fourth aspect of the present disclosure, a method for manufacturing a bulk acoustic wave resonator is provided, comprising:

[0026] providing a substrate;

[0027] forming a sacrificial layer on the substrate; wherein the sacrificial layer comprises a bottom surface and a top surface arranged oppositely, and a side surface connecting the bottom surface and the top surface; a cross section of the sacrificial layer obtained by a plane perpendicular to a surface of the substrate comprises a bottom edge, a top edge, and two side edges, each of the side edges comprises at least two first curves, the at least two first curves are not parallel, and an angle between a tangent line of each point on each of the first curves and a plane where the bottom edge is located satisfies: greater than 0°, and less than or equal to 45°;

[0028] forming a first electrode layer, a piezoelectric layer, and a second electrode layer arranged in sequence on the sacrificial layer;

[0029] removing the sacrificial layer to form a reflective structure comprising a cavity.

[0030] In some embodiments, the forming of the sacrificial layer on the substrate comprises:

[0031] forming a sacrificial material layer covering the substrate; wherein the sacrificial material layer comprises a central region and an edge region surrounding the central region, and the edge region comprises at least two sub-regions arranged in sequence from the center to the edge;

[0032] sequentially removing part of the sacrificial material layer in the at least two sub-regions to form a side surface of the sacrificial layer by a surface of the sacrificial material layer remaining in the at least two sub-regions; wherein each of the sub-regions comprises a first curved surface, and the first curved surface is a first curve obtained by a plane perpendicular to a surface of the substrate.

[0033] In some embodiments, the sequentially removing part of the sacrificial material layer in the at least two sub-regions comprises:

[0034] sequentially removing part of the sacrificial material layer in the at least two sub-regions by an etching process; wherein different etching parameters are used for different sub-regions to make the first curves corresponding to the first curved surfaces of different sub-regions not parallel.

[0035] The body acoustic wave resonator provided by the embodiment of the present disclosure comprises a reflection structure, a first electrode layer, a piezoelectric layer and a second electrode layer which are sequentially stacked on a substrate, wherein a cross section of the reflection structure comprises an opposite bottom edge and top edge, and a side edge connecting the bottom edge and the top edge, and the side edge comprises at least two first curves, the at least two first curves are not parallel, and an angle between a tangent of each point on each first curve and a plane where the bottom edge is located satisfies that the angle is greater than 0° and less than or equal to 45°.

[0036] The reflection structure in the embodiment of the present disclosure has the following advantages. On the one hand, the angle between the tangent of each point on each first curve included in the side edge and the plane where the bottom edge is located satisfies that the angle is greater than 0° and less than or equal to 45°, so that the side surface of the reflection structure and the corner where the side surface is connected with the bottom surface and the top surface are relatively gentle, the transverse / slanting tensile force between the piezoelectric layer crystals grown on the side surface is reduced, the probability of dislocation and fracture of the piezoelectric layer at the corner and the side surface of the reflection structure is reduced, the loss of the piezoelectric layer is reduced, and the performance of the device is improved. On the other hand, the side edge comprises at least two first curves, the length, shape or curvature of each curve can be changed to adjust the length of the normal projection of the side edge on the plane where the bottom edge is located, so that the length of the normal projection of the side edge on the plane where the bottom edge is located is within a required range, the probability of the first electrode layer extending to the side surface of the reflection structure is reduced, the parasitic capacitance of the device is reduced, and the performance of the device is further improved. In addition, the height of the reflection structure can be kept unchanged when the length, shape or curvature of each curve of the side edge of the reflection structure is adjusted, and the thickness of the resonator is not additionally increased, which is beneficial to the miniaturization of the device. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 A cross-sectional schematic view of a body acoustic wave resonator provided by the embodiment of the present disclosure is shown in FIG. 1.

[0038] Figure 2 A unit cell structure schematic view of aluminum nitride provided by the embodiment of the present disclosure is shown in FIG. 2.

[0039] Figure 3 A cross-sectional schematic view of a reflection structure provided by the embodiment of the present disclosure is shown in FIG. 3.

[0040] Figure 4 A cross-sectional schematic view of another reflection structure provided by the embodiment of the present disclosure is shown in FIG. 4.

[0041] Figure 5 A cross-sectional schematic view of another body acoustic wave resonator provided by the embodiment of the present disclosure is shown in FIG. 5.

[0042] Figure 6 A cross-sectional schematic view of the reflection structure shown in FIG. 3 and the reflection structure shown in FIG. 4 is shown in FIG. 6. Figure 5 A cross-sectional schematic view of the reflection structure shown in FIG. 3 and the reflection structure shown in FIG. 4 is shown in FIG. 6. Figure 3 A cross-sectional schematic view of the reflection structure shown in FIG. 3 and the reflection structure shown in FIG. 4 is shown in FIG. 6.

[0043] Figure 7 Yet another reflective structure and Figure 4 A cross-sectional view of the reflective structure shown;

[0044] Figure 8 Yet another reflective structure and Figure 4 A cross-sectional view of the reflective structure shown;

[0045] Figure 9 A cross-sectional view of yet another reflective structure provided by embodiments of the present disclosure;

[0046] Figure 10 A cross-sectional view of yet another reflective structure provided by embodiments of the present disclosure;

[0047] Figure 11 A cross-sectional view of yet another reflective structure provided by embodiments of the present disclosure;

[0048] Figure 12 A cross-sectional view of yet another reflective structure provided by embodiments of the present disclosure;

[0049] Figure 13 A cross-sectional view of yet another reflective structure provided by embodiments of the present disclosure;

[0050] Figure 14 A cross-sectional view of yet another reflective structure provided by embodiments of the present disclosure;

[0051] Figure 15 A cross-sectional view of yet another reflective structure provided by embodiments of the present disclosure;

[0052] Figure 16 A cross-sectional view of yet another reflective structure provided by embodiments of the present disclosure;

[0053] Figure 17 A flowchart of a method for manufacturing a bulk acoustic wave resonator provided by embodiments of the present disclosure;

[0054] Figures 18a to 18d A flowchart of forming a sacrificial layer provided by embodiments of the present disclosure;

[0055] Figure 19 A flowchart of a method for manufacturing a bulk acoustic wave resonator provided by embodiments of the present disclosure. DETAILED DESCRIPTION

[0056] Exemplary embodiments provided in this disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure may be implemented in various forms and should not be limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0057] The present disclosure is described in more detail below by way of example with reference to the accompanying drawings. The advantages and features of the present disclosure will become clearer from the following description and claims. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present disclosure.

[0058] In the embodiments of this disclosure, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0059] It should be noted that the technical solutions described in the embodiments of this disclosure can be combined arbitrarily without conflict.

[0060] Currently, fourth-generation (4G) mobile communication technology is the dominant protocol standard. With the gradual development of communication technology, fifth-generation (5G) mobile communication technology is gradually being implemented. In the future, the number of frequency bands used for communication will increase, and the distance between these bands will become smaller. To reduce mutual interference between frequency bands, many communication devices have strict specifications and standards. The main purpose of mobile communication technology development is to pursue higher bandwidth transmission rates to handle large amounts of information transmission.

[0061] The existence of multiple wireless communication standards worldwide necessitates that communication devices support various modes and frequency bands to facilitate roaming across regions. Therefore, the fabrication of high-performance, small-size, low-power, and low-cost acoustic wave devices (e.g., bulk acoustic resonators) is currently a key research focus in the industry.

[0062] Figure 1 This is a schematic cross-sectional view of a bulk acoustic resonator provided in an embodiment of this disclosure. Figure 1 As shown, the bulk acoustic wave resonator includes a substrate 100′, and a reflective structure 200′, a first electrode layer 300′, a piezoelectric layer 400′, and a second electrode layer 500′ sequentially stacked on the substrate 100′.

[0063] The reflective structure 200' is located on the surface of the substrate 100'. The reflective structure 200' includes a bottom surface and a top surface disposed opposite each other, and a side surface connecting the bottom surface and the top surface, with the bottom surface relatively close to the substrate 100'. Here, the cross-section of the reflective structure 200' obtained by a plane perpendicular to the surface of the substrate 100' is as follows: Figure 1 As shown, the cross-section includes a bottom edge and a top edge positioned opposite each other, as well as two side edges connecting the bottom edge and the top edge. The bottom edge corresponds to the bottom surface, the top edge corresponds to the top surface, and the two side edges correspond to the side surfaces.

[0064] For example, the bottom edge is parallel to the top edge, and the length of the bottom edge is greater than the length of the top edge, so that the cross-section of the reflective structure 200′ is generally trapezoidal, wherein the angle between the side edge and the bottom edge is acute, and the angle between the side edge and the top edge is obtuse.

[0065] like Figure 1 As shown, a first electrode layer 300′ is conformally deposited on the reflective structure 200′, and a piezoelectric layer 400′ is conformally deposited on the first electrode layer 300′, the surface of the reflective structure 200′ not covered by the first electrode layer 300′, and the surface of the substrate 100′. When the cross-section of the reflective structure 200′ is trapezoidal, the piezoelectric layer 400′ grown on it has a first corner α at the angle between the side and bottom of the reflective structure 200′, and the angle of the first corner α is equal to the angle between the side and bottom of the reflective structure 200′. The piezoelectric layer 400′ has a second corner β at the angle between the side and top of the reflective structure 200′, and the angle of the second corner β is equal to the angle between the side and top of the reflective structure 200′.

[0066] In bulk acoustic resonators, commonly used piezoelectric layers 400′ include aluminum nitride (AlN) and zinc oxide (ZnO), with AlN and ZnO belonging to the hexagonal wurtzite structure. Figure 2 This is a schematic diagram of the unit cell structure of AlN provided in an embodiment of this disclosure, as shown below. Figure 2 As shown, during the deposition of AlN or ZnO thin films, the grains grow along the C-axis to form a crystal pillar. At the positions of the first corner α and the second corner β, if the angle of the first corner α is too large or the angle of the second corner β is too small, dislocations are easily generated within the crystal pillar, leading to defects such as dislocations or fractures in the piezoelectric layer 400′, affecting the performance of the device, or even causing the device to fail.

[0067] In related technologies, in order to keep the crystal pillars of the piezoelectric layer 400′ in the same crystal orientation and to reduce the probability of defects such as dislocations or fractures in the piezoelectric layer 400′, the angle between the side and bottom of the reflective structure 200′ is usually reduced. Figure 3 A cross-sectional schematic diagram of another reflective structure provided in the disclosed embodiments, such as... Figure 3As shown, reducing the angle between the side and bottom of the reflective structure 200′ can reduce the first corner α and increase the second corner β, thus making the angle change of the piezoelectric layer more gradual and reducing the probability of defects such as dislocations and fractures in the piezoelectric layer 400′ at the corners. For example, when the angle between the side and bottom of the reflective structure (i.e., the first corner α) is less than or equal to 45°, and the angle between the side and top (i.e., the second corner β) is greater than or equal to 135°, the risk of dislocations or fractures in the piezoelectric layer is relatively small.

[0068] However, when the device design requires a thicker piezoelectric layer 400', the risk of breakage at the corners increases, necessitating a smaller angle between the side and bottom edges of the reflective structure 200'. This inevitably leads to the elongation of the side surface of the reflective structure 200', causing the first electrode layer 300' to extend to the side surface of the reflective structure 200', adversely affecting device performance, for example, increasing the device's parasitic capacitance.

[0069] In some embodiments, such as Figure 4 As shown, by making the side of the reflective structure 200′ curved, the transition of the piezoelectric layer 400′ at the second corner β is smoothed, which can reduce the probability of defects appearing in the piezoelectric layer 400′ at the second corner. However, at the first corner α, the angle change of the piezoelectric layer is still relatively large, and defects are prone to appear in the piezoelectric layer 400′. Ultimately, the probability of defects appearing in the piezoelectric layer 400′ at the first corner α is often reduced by lengthening the side of the reflective structure 200′.

[0070] Therefore, embodiments of this disclosure provide a bulk acoustic resonator. Figure 5 A schematic cross-sectional view of a bulk acoustic resonator provided in an embodiment of this disclosure is shown below. Figure 5 As shown, the bulk acoustic resonator includes a substrate 100, and a reflective structure 200, a first electrode layer 300, a piezoelectric layer 400, and a second electrode layer 500 sequentially stacked on the substrate 100.

[0071] The reflective structure 200 has a cross section perpendicular to the surface of the substrate 100. The cross section includes a bottom edge and a top edge that are disposed opposite to each other, and two side edges that connect the bottom edge and the top edge. Each side edge includes at least two segments of first curve SA. The at least two segments of first curve SA are not parallel. The angle between the tangent at each point on each segment of first curve SA and the plane containing the bottom edge satisfies the following condition: greater than 0° and less than or equal to 45°.

[0072] Here, the number of segments of the first curve SA included on the side can be two, three, four, or more. This disclosure does not impose any restrictions on this.

[0073] Here, the first curve SA can be a line segment or an arc.

[0074] It should be noted that in the present disclosure, the arc line refers to a curved line, that is, the arc line can be any curve except a straight line, a broken line and a line segment. For example, the arc line can be a circular arc, an elliptical arc, a parabolic curve, an exponential function curve or a logarithmic function curve, etc., or can be any curve.

[0075] Here, the at least two first curves included in the side edge can all be line segments, or all be arc lines, or at least one first curve is a line segment and the other first curves are arc lines (that is, there are both line segments and arc lines).

[0076] Here, the at least two first curves included in the side edge are not parallel. It can be understood that when the at least two first curves included in the side edge are all line segments, the at least two line segments are not parallel to each other. When the at least two first curves included in the side edge are all arc lines, the at least two arc lines are not parallel to each other. When the at least two first curves included in the side edge are both line segments and arc lines, the plurality of line segments are not parallel to each other, the plurality of arc lines are not parallel to each other, and the line segments and the arc lines are not parallel.

[0077] In some embodiments, the two side edges can be symmetrical, and the axis of symmetry is the vertical bisector of the bottom edge. In other embodiments, the two side edges can also be asymmetrical. When the two side edges are asymmetrical, the number of curves included in the two side edges or the length or shape or curvature of at least one curve is not completely the same.

[0078] Figures 6 to 8 The cross-sectional comparison diagram of the reflection structure and the reflection structure in the related art is shown. The reflection structure provided by the embodiments of the present disclosure is described below in combination with Figures 6 to 8 The reflection structure provided by the embodiments of the present disclosure is compared with the reflection structure in the related art. Here, it should be noted that the reflection structure provided by the embodiments of the present disclosure is not limited to the reflection structure shown in the figures. Figures 5 to 16 The dashed line in the figure is an extension line of the line segment or a tangent line of the first end point of the arc line, which is drawn to better illustrate the angle change of the first end point of the plurality of line segments or arc lines. The first end point of the arc line refers to the end point of the arc line relatively close to the substrate.

[0079] Figure 6 The cross-sectional comparison diagram of the reflection structure shown in Figure 5 and the reflection structure shown in Figure 3 is shown. As shown in Figure 6 in the related art, the side edge of the reflection structure 200' includes a line segment L1. For example, the angle between the line segment L1 and the bottom edge is 20°.

[0080] The side of the reflective structure 200 provided by the embodiments of the present disclosure includes a line segment SA1, a line segment SA2 and a line segment SA3. For example, the angle between the line segment SA1 and the bottom edge is 35°, the angle between the line segment SA2 and the plane where the bottom edge is located is 28°, and the angle between the line segment SA3 and the plane where the bottom edge is located is 20°. The angles between the three line segments and the plane where the bottom edge is located are all small, so that the first corner a of the piezoelectric layer 400 is small, and the second corner β is large, the angle change of the piezoelectric layer 400 is relatively gentle, and the probability of defects of the piezoelectric layer 400 at the first corner a and the second corner β is reduced.

[0081] Further, as shown in Figure 6 the reflective structure 200 provided by the embodiments of the present disclosure, the length of the orthographic projection of the side on the surface of the substrate 100 is smaller than the length of the orthographic projection of the line segment L1 on the surface of the substrate 100, which can reduce the probability of the first electrode layer 300 extending to the side of the reflective structure 200. As can be seen, the reflective structure 200 provided by the present disclosure can not only reduce the probability of defects such as dislocation and fracture of the piezoelectric layer 400, but also reduce the length of the orthographic projection of the side of the reflective structure 200 on the surface of the substrate 100, avoid the first electrode layer 300 extending to the side of the reflective structure 200, and thus improve the performance of the device. In addition, when adjusting the length, shape or curvature of each curve of the side of the reflective structure 200, the height thereof can be kept unchanged without additional increase in the thickness of the resonator, which is beneficial to the miniaturization of the device.

[0082] Figure 7 For another reflective structure provided by the embodiments of the present disclosure and Figure 4 a cross-sectional comparison diagram of the reflective structure is shown. As shown in Figure 7 in the related art, the side of the reflective structure 200' includes an arc line L2. For example, the angle between the tangent of the first end point of the arc line L2 and the bottom edge is 60°, and the angle between the tangent of the second end point of the arc line L2 and the plane where the bottom edge is located is 13°. The arc line L2 can reduce the probability of fracture of the piezoelectric layer 400 at the second corner β, but cannot reduce the probability of fracture of the piezoelectric layer 400 at the first corner a.

[0083] Here, the second end point of the arc line refers to the end point of the arc line relatively far away from the substrate, and the second end point is another end point of the arc line except the first end point.

[0084] The side of the reflective structure 200 provided by the embodiments of the present disclosure includes an arc line SA4 and an arc line SA5. For example, the angle between the tangent of the first end point of the arc line SA4 and the bottom edge is 33°, the angle between the tangent of the second end point of the arc line SA4 and the plane where the bottom edge is located is 15°, the angle between the tangent of the first end point of the arc line SA5 and the plane where the bottom edge is located is 40°, and the angle between the tangent of the second end point of the arc line SA5 and the plane where the bottom edge is located is 20°.

[0085] Since both the two arc lines are convex curves, the slope of each point on the convex curve gradually decreases from the first end point to the second end point, thus, the angle between the tangent of each point on the arc line SA4 and the plane where the bottom side lies is less than 33° and greater than 15°, and the angle between the tangent of each point on the arc line SA5 and the plane where the bottom side lies is less than 40° and greater than 20°. It can be seen that the angle between the tangent of each point on the two arc lines and the plane where the bottom side lies is relatively small, less than 45°, thus, the angle change of the piezoelectric layer 400 is relatively gentle, and the probability of defects of the piezoelectric layer 400 at the first corner α and the second corner β is reduced.

[0086] Further, as shown in FIG. 6, the sum of the lengths of the projections of the arc line SA4 and the arc line SA5 on the surface of the substrate 100 is equal to the length of the projection of the arc line L2 on the surface of the substrate 100, which can reduce the probability of the first electrode layer 300 extending to the side surface of the reflective structure 200. Figure 7

[0087] Therefore, compared with the related art, the reflective structure 200 provided in the embodiments of the present disclosure can reduce the probability of defects such as dislocation and fracture of the piezoelectric layer 400 on the basis of ensuring that the length of the projection of the side surface on the surface of the substrate 100 is not increased, thereby improving the performance of the device.

[0088] Figure 8 FIG. 7 is a cross-sectional view of another reflective structure 200 provided in the embodiments of the present disclosure and a comparison diagram of a cross section of the reflective structure 200. As shown in FIG. 7, in the related art, the side surface of the reflective structure 200' includes an arc line L2, parameters of which have been described in the analysis of FIG. 6, and thus are not described herein. Figure 4 Figure 8 Figure 7

[0089] The reflective structure 200 provided in the embodiments of the present disclosure has a side surface including a line segment SA6 and an arc line SA7. The arc line is a convex curve. For example, the angle between the line segment SA6 and the bottom side is 30°, the angle between the tangent of the first end point of the arc line SA7 and the plane where the bottom side lies is 40°, and the angle between the tangent of the second end point of the arc line SA7 and the plane where the bottom side lies is 15°. It can be seen that the angle between each point on the line segment SA6 and the arc line SA7 and the plane where the bottom side lies is relatively small, less than 45°, which can make the angle change of the piezoelectric layer 400 relatively gentle.

[0090] Further, as shown in FIG. 8, the sum of the lengths of the projections of the line segment SA6 and the arc line SA7 on the surface of the substrate 100 is equal to the length of the projection of the arc line L2 on the surface of the substrate 100. Therefore, the reflective structure 200 provided in the embodiments of the present disclosure can reduce the probability of defects such as dislocation and fracture of the piezoelectric layer 400 on the basis of ensuring that the length of the projection of the side surface on the surface of the substrate 100 is not increased, thereby improving the performance of the device. Figure 8

[0091] ​​​​​In summary, the reflection structure 200 provided by the present disclosure, on the one hand, the angle between the tangent of each point on the first curve SA included in the side edge and the plane where the bottom edge lies satisfies greater than 0° and less than or equal to 45°, which can make the angle of the piezoelectric layer 400 at the first corner α smaller and the angle at the second corner β larger, so that the angle change of the piezoelectric layer is relatively gentle, the probability of dislocation and fracture defects of the piezoelectric layer at the two corners is reduced, the loss of the piezoelectric layer is reduced, and the performance of the device is improved. On the other hand, the side edge includes at least two first curves, and the length of the side edge in the projection on the plane where the bottom edge lies can be adjusted by changing the shape or curvature of each curve (for example, changing the slope of the line segment with respect to the plane where the bottom edge lies, changing the shape or curvature of the arc, etc.), so that the length of the side edge in the projection on the plane where the bottom edge lies is within the required range, the probability of the first electrode layer extending to the side of the reflection structure is reduced, thereby reducing the parasitic capacitance of the device, and further improving the performance of the device. In addition, the length, shape or curvature of each curve of the side edge of the reflection structure 200 can be adjusted while keeping the height unchanged, without increasing the thickness of the resonator, which is beneficial to the miniaturization of the device.

[0092] Further, in some embodiments, when the first curve is a line segment, the angle between the line segment and the plane where the bottom edge lies satisfies: greater than or equal to 5° and less than or equal to 45°.

[0093] Here, no matter whether the first curve included in the side edge is a line segment or partially a line segment, the angle between these line segments and the plane where the bottom edge lies satisfies: greater than or equal to 5° and less than or equal to 45°.

[0094] It can be understood that, among the multiple line segments included in the side edge, if the angle between a line segment and the plane where the bottom edge lies is too small (for example, 1°), the projection of the line segment on the surface of the substrate 100 is relatively long, and the angle between another line segment and the plane where the bottom edge lies must be relatively large (for example, 35°) to reduce the length of the projection of the line segment on the surface of the substrate 100, so as to meet the requirement of the length of the projection of the side edge on the surface of the substrate 100. The side edge formed in this way is relatively steep.

[0095] In the present embodiment, the angle between the line segment and the plane where the bottom edge lies is further limited to greater than or equal to 5° and less than or equal to 45°, so that each line segment is relatively gentle, the overall side edge is relatively gentle, and the quality of the piezoelectric layer 400 formed is better, which is more conducive to reducing the loss of the piezoelectric layer 400 and improving the performance of the piezoelectric layer 400.

[0096] In some embodiments, when the first curve connected to the bottom edge is a line segment, the angle between the line segment and the bottom edge satisfies: greater than or equal to 10° and less than or equal to 25°.

[0097] The experimental studies disclosed herein show that when the angles of the line segments connected to the bottom edge are 10°, 25°, and 35°, the yields of multiple bulk acoustic wave resonators on a single wafer are 97%, 75%, and 58%, respectively. It is evident that when the angle of the line segments connected to the bottom edge is within the range of 10° to 25°, the sides become smoother, resulting in a higher quality piezoelectric layer 400, which is more conducive to improving the performance of the piezoelectric layer 400, thereby increasing the device yield to over 75%.

[0098] Similarly, in some embodiments, when the first curve connected to the top edge is a line segment, the angle between the line segment and the plane containing the bottom edge satisfies the following condition: greater than or equal to 10° and less than or equal to 25°. This also makes the sides smoother, which is more conducive to improving the performance of the piezoelectric layer 400.

[0099] In some embodiments, such as Figure 5 As shown, when the multiple first curves included in the side are all line segments, the angle between these multiple line segments and the plane containing the bottom edge can gradually decrease along the direction from the bottom edge to the top edge. In this way, the side can be made smoother, which is more conducive to improving the performance of the piezoelectric layer 400.

[0100] In some embodiments, when the multiple first curves included in the side are all line segments, the angle between the multiple line segments and the plane containing the bottom edge can gradually increase along the direction from the bottom edge to the top edge. Figure 9 A cross-sectional schematic diagram of another reflective structure provided in this disclosure embodiment, as shown below. Figure 9 As shown, the angle between line segment SA8 and the plane containing the base is 10°, and the angle between line segment SA9 and the plane containing the base is 20°. 10 The angle between the segment and the plane containing the bottom edge is 30°. Along the direction from the bottom edge to the top edge, the angle between this segment and the plane containing the bottom edge gradually increases, which makes the side edge smoother and is more conducive to improving the performance of the piezoelectric layer 400.

[0101] In some embodiments, when the first curve is an arc, the angle between the tangent at the first endpoint and the plane containing the bottom edge satisfies: greater than or equal to 5° and less than or equal to 45°, and the angle between the tangent at the second endpoint and the plane containing the bottom edge satisfies: greater than 0° and less than or equal to 45°.

[0102] More preferably, the angle between the tangent at each point on the arc and the plane containing the base edge satisfies the following condition: greater than or equal to 5° and less than or equal to 45°.

[0103] Based on the above analysis that the angle between the line segment and the plane of the bottom side satisfies greater than or equal to 5° and less than or equal to 45°, when the tangent of the first endpoint of the arc line satisfies: greater than or equal to 5° and less than or equal to 45°, or the tangent of each point on the arc line satisfies: greater than or equal to 5° and less than or equal to 45°, the side can be made more gentle as a whole, and the quality of the piezoelectric layer 400 formed is better, which is more conducive to improving the performance of the piezoelectric layer 400.

[0104] Further, in some embodiments, when the first curve connected with the bottom side is an arc line, the tangent of the first endpoint of the arc line and the bottom side satisfies: greater than or equal to 10° and less than or equal to 25°.

[0105] More preferably, when the first curve connected with the bottom side is an arc line, the tangent of each point on the arc line and the bottom side satisfies: greater than or equal to 10° and less than or equal to 25°.

[0106] Experimental research of the present disclosure shows that when the tangent of each point on the arc line connected with the bottom side and the bottom side is within the range of 10° to 25°, the side can be made more gentle, the quality of the piezoelectric layer 400 formed is better, which is more conducive to improving the performance of the piezoelectric layer 400, thereby improving the yield of the device to more than 75%.

[0107] Similarly, in some embodiments, when the first curve connected with the top side is an arc line, the tangent of the second endpoint of the arc line and the plane of the bottom side satisfies: greater than or equal to 10° and less than or equal to 25°.

[0108] More preferably, when the first curve connected with the top side is an arc line, the tangent of each point on the arc line and the bottom side satisfies: greater than or equal to 10° and less than or equal to 25°.

[0109] Experimental research of the present disclosure shows that when the tangent of each point on the arc line connected with the top side and the plane of the bottom side is within the range of 10° to 25°, the side can also be made more gentle, the quality of the piezoelectric layer 400 formed is better, which is more conducive to improving the performance of the piezoelectric layer 400, thereby greatly improving the yield of the device.

[0110] In some embodiments, the arc line can be a concave curve that is concave to one side of the substrate 100. The concave curve is smooth and continuous, and has no inflection point. It can be understood that the tangent of each point on the concave curve and the plane of the bottom side gradually increases from the first endpoint to the second endpoint.

[0111] In some embodiments, the arc line can also be a convex curve that is convex away from one side of the substrate 100. The convex curve is smooth and continuous, and has no inflection point.

[0112] In some embodiments, such as Figure 7 As shown, the multiple first curve segments included in the side can all be convex curves.

[0113] In some embodiments, the multiple first curves included in the side edge may all be concave curves. Figure 10 A cross-sectional schematic diagram of another reflective structure provided in this disclosure embodiment, as shown below. Figure 10 As shown, arc SA 14 , arc SA 15 and the arc SA 16 All are concave curves.

[0114] In some embodiments, the multiple first curves included in the side may include both convex and concave curves. Figure 11 A cross-sectional schematic diagram of another reflective structure provided in this disclosure embodiment, as shown below. Figure 11 As shown, curve SA 29 It is a convex curve, curve SA 30 It is a concave curve, curve SA 31 It is a convex curve.

[0115] In some embodiments, when the multiple first curves included in the side edge are all convex curves, the angle between the tangent of the first endpoint of the multiple convex curves and the plane containing the bottom edge can gradually increase or gradually decrease along the direction from the bottom edge to the top edge. In this way, the side edge can be made smoother, which is more conducive to improving the performance of the piezoelectric layer 400. Figure 12 A cross-sectional schematic diagram of another reflective structure provided in this disclosure embodiment, as shown below. Figure 12 As shown, arc SA 11 The angle between the tangent at the first endpoint and the plane containing the base is 18°, and the arc SA 12 The angle between the tangent at the first endpoint and the plane containing the base is 38°, and the arc SA 13 The angle between the tangent at the first endpoint and the plane containing the bottom edge is 43°. The angle between the tangent at the first endpoint of the multi-segment convex curve and the plane containing the bottom edge gradually increases, and the side of the reflective structure 200 is relatively gentle.

[0116] In some embodiments, when the multiple first curves included in the side edge are all concave curves, the angle between the tangent of the first endpoint of the multiple concave curves and the plane containing the bottom edge can gradually increase or gradually decrease along the direction from the bottom edge to the top edge. This makes the side edge smoother, which is more conducive to improving the performance of the piezoelectric layer 400. Figure 10 As shown, arc SA 14 The angle between the tangent at the first endpoint and the plane containing the base is 18°, and the arc SA 15 The angle between the tangent at the first endpoint and the plane containing the base is 13°, and the arc SA 16The angle between the tangent of the first end point of the first curve and the plane of the bottom edge is 8°, the angle between the tangent of the first end point of the multi-segment concave curve and the plane of the bottom edge gradually decreases, and the side edge of the reflective structure 200 is relatively flat.

[0117] In some embodiments, when the side edge comprises a multi-segment first curve SA, the number of arcs and line segments is not limited by the present disclosure. The relative positions of the arcs and line segments are also not limited by the present disclosure, and the arcs can be on the line segments or the line segments can be on the arcs.

[0118] In some embodiments, the at least two segments of the first curve comprise at least two line segments and at least one arc, wherein the arc is located between the two adjacent line segments. Here, the arc can be regarded as chamfering at the joint of the two adjacent line segments, so that the transition of the two line segments is smoother, which can buffer the growth of the crystal column in the piezoelectric layer and reduce the problem of piezoelectric layer fracture, thereby improving the quality of the piezoelectric layer 400.

[0119] Figure 13 Another schematic diagram of a reflective structure provided by an embodiment of the present disclosure is shown in FIG. 2B. As shown in FIG. 2B, the side edge of the reflective structure comprises a line segment SA Figure 13 17 , an arc SA 18 , a line segment SA 19 , an arc SA 20 , and a line segment SA 21 . The arcs SA 18 and SA 20 make the side edge of the reflective structure 200 more flat, which is beneficial to improving the performance of the piezoelectric layer 400.

[0120] In some embodiments, among the multi-segment first curve comprising the side edge, the angle between the tangent of each point on the first curve relatively close to the bottom edge and the plane of the bottom edge is greater than the angle between the tangent of each point on the first curve relatively close to the top edge and the plane of the bottom edge; in the plane of the substrate, the length of the orthographic projection of the first curve relatively close to the bottom edge is less than the length of the orthographic projection of the first curve relatively close to the top edge, in other words, along the direction from the bottom edge to the top edge, the length of the orthographic projection of the multi-segment first curve comprising the side edge in the plane of the substrate gradually increases.

[0121] Here, the first curve can be a line segment or an arc, and the arc can be a convex curve or a concave curve.

[0122] For example, the ratio of the length of the orthographic projection of the first curve connected to the bottom edge in the plane of the substrate to the length of the orthographic projection of the side edge in the plane is less than 50%.

[0123] ​Here, by setting the length of the first curve connected to the bottom edge to be relatively short, even if a dislocation occurs in the piezoelectric layer 400 at the first corner α, the proportion of dislocated crystal pillars in the piezoelectric layer 400 can be reduced, thereby decreasing the impact of dislocated crystal pillars on the performance of the piezoelectric layer 400 and also reducing the impact on the upper second electrode layer 500. Furthermore, setting the length of the first curve connected to the bottom edge to be relatively short also helps to improve the overall physical structural strength of the device.

[0124] In some embodiments, among the multiple first curves included in the side, the angle between the tangent of each point on the first curve that is relatively closer to the bottom edge and the plane where the bottom edge is located is smaller than the angle between the tangent of each point on the first curve that is relatively closer to the top edge and the plane where the bottom edge is located; on the plane where the substrate is located, the orthographic projection length of the first curve that is relatively closer to the bottom edge is greater than the orthographic projection length of the first curve that is relatively closer to the top edge. In other words, along the direction from the bottom edge to the top edge, the orthographic projection length of the multiple first curves included in the side on the plane where the substrate is located gradually decreases.

[0125] For example, the proportion of the orthographic projection length of the first curve connected to the bottom edge in the plane of the substrate to the orthographic projection length of the side edge in the same plane is greater than or equal to 30%.

[0126] Here, when the length of the first curve connected to the bottom edge is set to be longer, the side edge is more gentle, the quality of the piezoelectric layer 400 formed is better, and it is more conducive to improving the performance of the piezoelectric layer 400.

[0127] In some embodiments, the side may further include:

[0128] The second curve is parallel to the bottom edge and is located between two adjacent segments of the first curve.

[0129] Here, the second curve is a line segment parallel to the base. The angle between the second curve and the plane containing the base is 0°.

[0130] Figure 14 A cross-sectional schematic diagram of another reflective structure provided in this disclosure embodiment, as shown below. Figure 14 As shown, the side of the reflective structure 200 includes a first curve SA. 22 Second curve SB1, first curve SA 23 The second curve SB2 and the first curve SA 24 Here, the first curve SA 23 The first endpoint is connected to the second curve SB1, and the first curve SA 24 The first endpoint is connected to the second curve SB2, which makes the side of the reflective structure 200 more gentle, which is beneficial to improving the performance of the piezoelectric layer 400.

[0131] In addition, the reflection structure 200 can be regarded as a plurality of stacked sub-reflection structures, and each first curve is a side of a sub-reflection structure. For example, the first curve SA 22 is a side of a first sub-reflection structure, the first curve SA 23 is a side of a second sub-reflection structure, and the first curve SA 24 is a side of a third sub-reflection structure. For example, the reflection structure 200 is a cavity formed by removing a sacrificial layer after forming a first electrode layer, a piezoelectric layer, and a second electrode layer on the sacrificial layer. In the preparation process of the reflection structure 200 provided in this embodiment, a first part of the sacrificial layer can be deposited first, and then a second part of the sacrificial layer is deposited to form a side corresponding to the second sub-reflection structure after the side corresponding to the first sub-reflection structure is formed on the side of the first part of the sacrificial layer. Finally, a third part of the sacrificial layer is deposited to form a side corresponding to the third sub-reflection structure. The forming process of such a reflection structure is simpler, which can shorten the preparation period and reduce the preparation cost.

[0132] Here, the two first curves connected by the second curve can be an arc or a line segment. The present disclosure does not limit this.

[0133] When the second end point of the arc is connected to the second curve, the tangent line of the arc at the second end point and the plane on which the bottom side lies has an included angle close to 0°, so that the arc is smoothly connected to the second curve at the second end point.

[0134] Here, the second curve can be arranged between each group of adjacent first curves, or the second curve can be arranged between part of the adjacent first curves. The present disclosure does not limit this.

[0135] In some embodiments, the bulk acoustic resonator can be a film bulk acoustic resonator (FBAR), and the reflection structure 200 of the FBAR is a cavity. For example, the reflection structure 200 of the FBAR is a cavity. Figures 5 to 14 The reflection structures 200 shown in the figures are all cavities.

[0136] In some embodiments, the bulk acoustic resonator can also be a solidly mounted resonator (SMR). The reflection structure 200 of the SMR is a Bragg reflection layer. The Bragg reflection layer is composed of high acoustic impedance layers and low acoustic impedance layers with a thickness of one-quarter wavelength alternately stacked. If viewed from the high acoustic impedance layer downward, the equivalent impedance of the Bragg reflection layer is infinite, and if viewed from the low acoustic impedance layer downward, the equivalent impedance of the Bragg reflection layer is zero. The Bragg reflection layer is used to provide an acoustic wave boundary.

[0137] In some embodiments, to improve the performance of the piezoelectric layer 400 in the SMR, the reflective structure of the SMR may be configured to include: an alternately stacked first reflective grating and a second reflective grating, wherein the corresponding side of the first reflective grating includes a first sub-curve, the corresponding side of the second reflective grating includes a second sub-curve, and the first sub-curve and the second sub-curve are not parallel.

[0138] Figure 15 This is a cross-sectional schematic diagram of another reflective structure provided in an embodiment of this disclosure. (See diagram below.) Figure 15 As shown, the reflective structure 200 includes alternating layers of a first reflective grating 201 and a second reflective grating 202, wherein the first reflective grating 201 corresponds to a first sub-curve SA. 25 The second sub-curve SA corresponding to the second reflective grating 202 26 By not being parallel, the sides of the reflective structure 200 can be made relatively flat while ensuring that the orthographic projection length of the side of the reflective structure 200 on the surface of the substrate 100 is within the required range. This makes the piezoelectric layer relatively flat and improves the performance of the piezoelectric layer.

[0139] Figure 16 This is a cross-sectional schematic diagram of another reflective structure provided in an embodiment of this disclosure. (See diagram below.) Figure 16 As shown, the reflective structure 200 includes a first portion 210 and a second portion 220. The first portion 210 includes alternating layers of a first reflective grating 201 and a second reflective grating 202. The side of the first reflective grating 201 includes a first sub-curve SA. 25 The side corresponding to the second reflective grating 202 includes the second sub-curve SA. 26 The first sub-curve SA 25 Second sub-curve SA 26 The second part includes alternating layers of a third reflective grating 203 and a fourth reflective grating 204. The third reflective grating 203 and the first reflective grating 201 are made of the same material and have the same thickness. The fourth reflective grating 204 and the second reflective grating 202 are made of the same material and have the same thickness. The side of the third reflective grating 203 includes a third sub-curve SA. 27 The side corresponding to the fourth reflective grating 204 includes the fourth sub-curve SA. 28 The third sub-curve SA 27 and the fourth sub-curve SA 28 Non-parallel, and the third subcurve SA 27 and the first sub-curve SA 25 Non-parallel, fourth sub-curve SA 28 Second sub-curve SA 26 Not parallel. Thus, by making the third subcurve SA 27 The angle between the curve and the plane containing the bottom edge is less than that of the first sub-curve SA. 25 The angle between the curve and the plane containing the base edge makes the fourth subcurve SA28 The angle between the curve and the plane containing the bottom edge is less than that of the second subcurve SA. 26 The angle between the reflective structure 200 and the plane containing the bottom edge can also make the side of the reflective structure 200 more gentle, thereby making the piezoelectric layer more gentle and improving the performance of the piezoelectric layer.

[0140] In some embodiments, such as Figure 5 As shown, the angle between the side and bottom edge of the first electrode layer 300 satisfies the condition that it is greater than or equal to 5° and less than or equal to 15°. This makes the piezoelectric layer 400 located on the side of the first electrode layer 300 relatively flat, reducing the risk of breakage of the piezoelectric layer 400 and improving its performance.

[0141] Preferably, the angle between the side and bottom edge of the first electrode layer 300 is greater than or equal to 7° and less than or equal to 12°, so as to further reduce the risk of breakage of the piezoelectric layer 400 and improve its performance.

[0142] In summary, the bulk acoustic wave resonator provided in this embodiment can make the first corner α and the second corner β of the piezoelectric layer larger, so that the angle change of the piezoelectric layer is more gradual, reducing the probability of defects such as dislocations and fractures in the piezoelectric layer at the two corners, reducing the loss of the piezoelectric layer and improving the performance of the device. It can also make the orthographic projection length of the side of the reflective structure on the plane where the bottom edge is located within the required range, reducing the probability of the first electrode layer extending to the side of the reflective structure, thereby reducing the parasitic capacitance of the device and further improving the performance of the device.

[0143] This disclosure also provides a method for fabricating a bulk acoustic resonator. Figure 17 This is a schematic flowchart illustrating the fabrication method of a bulk acoustic resonator provided in an embodiment of this disclosure. Figure 17 As shown, the manufacturing method includes:

[0144] S100: Provides a substrate;

[0145] S200: A sacrificial layer is formed on a substrate; wherein the sacrificial layer includes a bottom surface and a top surface disposed opposite each other, and a side surface connecting the bottom surface and the top surface; the cross section of the sacrificial layer obtained by a plane perpendicular to the surface of the substrate includes a bottom edge, a top edge and two side edges, each side edge including at least two first curve segments, the at least two first curve segments being non-parallel, and the angle between the tangent at each point on each first curve segment and the plane containing the bottom edge satisfies: greater than 0° and less than or equal to 45°;

[0146] S300: A first electrode layer, a piezoelectric layer, and a second electrode layer are sequentially formed on the sacrificial layer;

[0147] S400: Remove the sacrificial layer to form a reflective structure including a cavity.

[0148] Here, the bulk acoustic resonator is an FBAR.

[0149] In step S100, a substrate is provided.

[0150] The substrate may be composed of silicon (Si), germanium (Ge), or silicon-on-insulator (SOI) on an insulating substrate 100.

[0151] In step S200, a sacrificial layer is formed on the substrate.

[0152] Understandably, this sacrificial layer is removed in subsequent processes to form a cavity-type reflective structure. Therefore, the bottom, top, and side surfaces of the sacrificial layer are the same as the bottom, top, and side surfaces of the reflective structure.

[0153] In this step, the sacrificial layer can be adjusted to have a specific shape according to the desired shape of the final reflective structure.

[0154] In some embodiments, step S200, the step of forming a sacrificial layer with a specific shape on the substrate, includes:

[0155] A sacrificial material layer is formed over a substrate; wherein the sacrificial material layer includes a central region and an edge region surrounding the central region, and the edge region includes at least two sub-regions arranged sequentially from the center to the edge;

[0156] Partial sacrificial material layers are removed sequentially from at least two sub-regions so that the surfaces of the remaining sacrificial material layers in the at least two sub-regions form the side surfaces of the sacrificial layers; wherein each sub-region includes a first curved surface, the first curved surface being intersected by a plane perpendicular to the substrate surface to obtain a first curve.

[0157] Figures 18a to 18d This is a schematic diagram illustrating the process of forming a sacrificial layer according to an embodiment of this disclosure. It should be understood that... Figures 18a to 18d The operations shown are not necessarily performed in exact order. Instead, the steps can be processed in reverse order or simultaneously. Additionally, other operations can be added to these processes, or one or more operations can be removed from them.

[0158] The following is combined Figures 18a-18d This paper describes the specific implementation process of the sacrifice layer provided in the embodiments of this disclosure.

[0159] See Figure 18a A sacrificial material layer 600 is formed covering the substrate 100; the sacrificial material layer includes a central region 110 and an edge region 120 surrounding the central region. Here, only a portion of the central region 110 and the edge region 120 are shown. It should be understood that in a cross-sectional view of the complete sacrificial material layer 600, the edge region 120 should be symmetrically located on both sides of the central region 110.

[0160] Here, the material of the sacrificial material layer 600 can include silicon dioxide (SiO2), photoresist, polyimide, porous silicon, aluminum, phospho-silicate glass (PSG), and the like.

[0161] Here, the sacrificial material layer 600 can be formed by a chemical vapor deposition process (CVD), a physical vapor deposition process (PVD), an atomic layer deposition process (ALD), or the like. The chemical vapor deposition process can include plasma-enhanced chemical vapor deposition (PECVD) and low-pressure chemical vapor deposition (LPCVD), and the like.

[0162] Referring to Figures 18b to 18d The sacrificial material layer 600 in the at least two sub-regions is sequentially removed, so that the surface of the remaining sacrificial material layer 600 in the at least two sub-regions forms a side surface of the sacrificial layer.

[0163] Here, the sacrificial material layer 600 located in the central region 110 is not etched, and the sacrificial material layer 600 located in the central region 110 forms a top surface of the sacrificial layer relative to the surface of the substrate 100. The remaining sacrificial material layer 600 located in the central region 110 and the edge region 120 forms a bottom surface of the sacrificial layer relative to the surface of the substrate 100.

[0164] Referring to Figure 18b A first mask layer 701 is formed on the sacrificial material layer 600, wherein the first mask layer 701 exposes the first sub-region. Then, the sacrificial material layer 600 in the first sub-region is etched through the first mask layer 701, so that the surface of the remaining sacrificial material layer 600 in the first sub-region forms a first curved surface.

[0165] Here, the sacrificial material layer 600 can be etched by a dry etching process. The dry etching process can include plasma etching, reactive ion etching (RIE), ion beam etching, sputtering etching, and the like. The plasma etching can include inductively coupled plasma (ICP) etching and capacitively coupled plasma (CCP) etching, and the like. The dry etching process includes a physical etching process and a chemical etching process. The physical etching process is more likely to form a flat surface, while the chemical etching process is more likely to form a curved surface. The proportion of the physical etching process and the chemical etching process can be controlled by adjusting the etching parameters such as the gas ratio of the etching process, the etching power, and the cavity pressure.

[0166] In the present disclosure, the etching parameters of the dry etching process can be adjusted according to the side of the sacrificial layer that is finally desired. It can be understood that the slope of the line segment, the shape of the arc, and the tangent of the first and second endpoints of the arc can all be controlled by adjusting the etching parameters of the dry etching process. The projection length of the first curve on the plane of the bottom side can be controlled by adjusting the exposure area of the first mask layer 701.

[0167] Referring to Figure 18c After the first first curve is formed in the first sub-region, the first mask layer 701 is removed, and then a second mask layer 702 is formed on the sacrificial material layer 600, wherein the second mask layer 702 exposes the second sub-region. Then, the sacrificial material layer 600 in the second sub-region is etched through the second mask layer 702, so that the surface of the remaining sacrificial material layer 600 in the second sub-region forms a second first curve.

[0168] Referring to Figure 18d After the second first curve is formed in the second sub-region, the second mask layer 702 is removed, and then a third mask layer 703 is formed on the sacrificial material layer 600, wherein the third mask layer 703 exposes the third sub-region. Then, the sacrificial material layer 600 in the third sub-region is etched through the third mask layer 703, so that the surface of the remaining sacrificial material layer 600 in the third sub-region forms a third first curve.

[0169] Here, different etching parameters can be used for different sub-regions, so that the first curves corresponding to the first curves of different sub-regions are not parallel.

[0170] In some embodiments, after the sacrificial material layer 600 in each sub-region is etched by the dry etching process, the surface of the etched sacrificial material layer 600 can be passivated to protect the shape of the formed side surface.

[0171] In some embodiments, when the side surface includes a second curve, one way is to form a mask layer that exposes a certain sub-region and form a second curve corresponding to the second curve in the sub-region, the second curve being a plane. Another way is to form a first curve corresponding to the first curve in a certain sub-region, and by adjusting the etching parameters, a part of the surface of the remaining sacrificial material layer in the sub-region forms a first curve, and another part of the surface of the remaining sacrificial material layer forms a second curve.

[0172] In step S300, a first electrode layer, a piezoelectric layer, and a second electrode layer are sequentially formed on the sacrificial layer.

[0173] Here, the constituent material of the first electrode layer can include an electrically conductive metal such as aluminum (Al), molybdenum (Mo), ruthenium (Ru), iridium (Ir), or platinum (Pt), or an electrically conductive material composed of an alloy of the above electrically conductive metals; and the constituent material of the second electrode layer can include an electrically conductive metal such as aluminum (Al), molybdenum (Mo), ruthenium (Ru), iridium (Ir), or platinum (Pt), or an electrically conductive material composed of an alloy of the above electrically conductive metals. The constituent materials of the first electrode layer and the second electrode layer can be the same or different. For example, the constituent materials of the first electrode layer and the second electrode layer can include molybdenum.

[0174] The constituent material of the piezoelectric layer can include a material having piezoelectric properties. For example, aluminum nitride, zinc oxide, lithium tantalate, lead zirconate titanate, or barium titanate. The constituent material of the piezoelectric layer can also include a material having piezoelectric properties doped with a transition metal or a rare metal, for example, scandium-doped aluminum nitride.

[0175] It can be understood that the side surface of the reflection structure provided by the embodiments of the present disclosure can greatly reduce the defects of the aluminum nitride piezoelectric layer and the zinc oxide piezoelectric layer, and for piezoelectric layers of other materials, the reflection structure can also make the piezoelectric layer relatively flat, thereby improving the physical structure strength of the entire device.

[0176] In step S400, the sacrificial layer is removed to form a reflection structure including a cavity.

[0177] Here, a release hole extending through the piezoelectric layer or extending through the first electrode layer, the piezoelectric layer, and the second electrode layer and extending to the sacrificial layer can be formed first, and the sacrificial layer is removed through the release hole. At the position where the sacrificial layer is removed, a cavity is formed, which is the reflection structure.

[0178] Here, the sacrificial layer can be removed by a hydrogen fluoride vapor release process. Specifically, the bulk acoustic wave resonator with the release hole is placed in hydrogen fluoride vapor, the hydrogen fluoride vapor contacts and reacts with the sacrificial layer through the release hole, thereby removing the sacrificial layer and forming a cavity.

[0179] Figure 19 A flowchart of another method for manufacturing a bulk acoustic wave resonator provided by the embodiments of the present disclosure is shown. In some embodiments, when the bulk acoustic wave resonator is an SMR, the reflection structure thereof is a Bragg reflection layer, and the method for manufacturing the bulk acoustic wave resonator is as shown in Figure 19 , which includes:

[0180] S100': providing a substrate,

[0181] S200' : forming a reflecting structure on the substrate; wherein the reflecting structure comprises a plurality of reflecting gratings stacked in sequence, the reflecting structure comprises a bottom surface and a top surface arranged oppositely, and a side surface connecting the bottom surface and the top surface; a cross section of the reflecting structure obtained by a plane perpendicular to a surface of the substrate comprises a bottom edge, a top edge and two side edges, each of the side edges comprises at least two first curves, the at least two first curves are not parallel, and an angle between a tangent line of each point on each of the first curves and a plane where the bottom edge is located satisfies: greater than 0° and less than or equal to 45°;

[0182] S300' : sequentially forming a first electrode layer, a piezoelectric layer and a second electrode layer on the reflecting structure.

[0183] Here, the substrate in step S100' is the same as the substrate in the above method for manufacturing the FBAR, and thus is not described herein again. Step 300' is the same as the steps of forming the first electrode layer, the piezoelectric layer and the second electrode layer in the above method for manufacturing the FBAR, and thus is not described herein again.

[0184] In step S200', the reflecting structure is formed on the substrate.

[0185] Here, the reflecting structure is a Bragg reflecting layer.

[0186] In some embodiments, step S200' specifically comprises:

[0187] forming a reflecting material layer on the substrate; wherein the reflecting material layer comprises first reflecting material layers and second reflecting material layers stacked alternately, the first reflecting material layers and the second reflecting material layers have different etching rates under the same etching parameter; the reflecting material layer comprises a central region and an edge region surrounding the central region;

[0188] adopting a dry etching process to remove part of the reflecting material layer in the edge region, so that a surface of the remaining reflecting material layer in the edge region forms a side surface of the reflecting structure, a part of the side surface corresponding to the first reflecting grating comprises a first sub-surface, a part of the side surface corresponding to the second reflecting grating comprises a second sub-surface, and the first sub-surface and the second sub-surface are cut by a plane perpendicular to a surface of the substrate to form a first sub-curve and a second sub-curve.

[0189] Here, the reflecting material layer in the central region is not etched, and a surface of the reflecting material layer in the central region relatively far away from the surface of the substrate forms a top surface of the reflecting structure. The remaining reflecting material layer in the central region and the edge region relatively close to the surface of the substrate forms a bottom surface of the reflecting structure.

[0190] Here, the etching rate of the first reflective material layer and the second reflective material layer under the same etching parameter is different, that is, the first reflective material layer and the second reflective material layer have an etching selectivity ratio. When the dry etching process is used to etch the first reflective material layer and the second reflective material layer at the same time, the first reflective material layer and the second reflective material layer are etched to different degrees. Therefore, the corresponding side surface of the first reflective grating includes the first sub-surface, and the corresponding side surface of the second reflective grating includes the second sub-surface, and the shapes of the first sub-surface and the second sub-surface are different, that is, the first sub-surface and the second sub-surface are not parallel, and the first sub-curve corresponding to the first sub-surface and the second sub-curve corresponding to the second sub-surface are also not parallel.

[0191] In some embodiments, different etching parameters can also be used to etch different sub-regions, and a reflective structure 200 as shown in FIG. 2B can be obtained. Figure 16

[0192] In addition, the embodiment of the present disclosure also provides a filter formed by cascading the plurality of bulk acoustic resonators.

[0193] The embodiment of the present disclosure also provides a multiplexer including the filter as described above. The multiplexer includes a diplexer, a triplexer, a quadruplexer, and the like. The features disclosed in the several method or device embodiments provided by the present disclosure can be combined arbitrarily without conflict, to obtain new method embodiments or device embodiments.

[0194] In the embodiments provided by the present disclosure, it should be understood that the disclosed device, system and method can be implemented in other ways. The above are merely specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any variations or replacements within the technical range disclosed by the present disclosure can be easily conceived by those skilled in the art, and should be encompassed by the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.​

Claims

1. A bulk acoustic wave resonator, characterized by, include: Substrate; A reflective structure is located on the surface of the substrate, wherein the cross-section of the reflective structure is perpendicular to the substrate surface. The cross-section includes a bottom edge and a top edge disposed opposite each other, and two side edges connecting the bottom edge and the top edge. The bottom edge is relatively close to the substrate. Each side edge includes at least two first curve segments, one of which connects to the bottom edge and the other connects to the top edge. The at least two first curve segments are not parallel. The angle between the tangent at each point on each first curve segment and the plane containing the bottom edge satisfies the following condition: greater than 0° and less than or equal to 45°. A first electrode layer, a piezoelectric layer, and a second electrode layer, stacked sequentially, are located on the reflective structure.

2. The bulk acoustic resonator of claim 1, wherein, The at least two segments of the first curve are both line segments; or... Both of the at least two segments of the first curve are arcs; or... Of the at least two first curve segments, at least one of the first curve segments is a line segment, and the other first curve segments are arcs.

3. The bulk acoustic resonator of claim 1, wherein, The first curve includes a line segment, and the angle between the line segment and the plane containing the bottom edge satisfies the following conditions: greater than or equal to 5° and less than or equal to 45°.

4. The bulk acoustic resonator of claim 3, wherein, The angle between the line segment connected to the bottom edge and the bottom edge satisfies the following conditions: greater than or equal to 10° and less than or equal to 25°.

5. The bulk acoustic resonator of claim 3, wherein, The angle between the line segment connected to the top edge and the plane containing the bottom edge satisfies the following conditions: greater than or equal to 10° and less than or equal to 25°.

6. The bulk acoustic resonator of claim 1, wherein, The first curve includes an arc, and the angle between the tangent at each point on the arc and the plane containing the bottom edge satisfies the following conditions: greater than or equal to 5° and less than or equal to 45°.

7. The bulk acoustic resonator of claim 6, wherein, The arc includes a concave curve that dips into the substrate, or a convex curve that protrudes from the substrate.

8. The bulk acoustic resonator of claim 6, wherein, The angle between the tangent at each point on the arc connected to the bottom edge and the plane containing the bottom edge satisfies the following conditions: greater than or equal to 10° and less than or equal to 25°.

9. The bulk acoustic resonator of claim 1, wherein, In two adjacent segments of the first curve, the angle between the tangent at each point on the first curve relatively closer to the bottom edge and the plane containing the bottom edge is greater than the angle between the tangent at each point on the first curve relatively closer to the top edge and the plane containing the bottom edge; along the direction from the bottom edge to the top edge, the orthographic projection length of the at least two segments of the first curve on the plane containing the substrate gradually increases; or, In two adjacent segments of the first curve, the angle between the tangent at each point on the first curve relatively closer to the bottom edge and the plane containing the bottom edge is smaller than the angle between the tangent at each point on the first curve relatively closer to the top edge and the plane containing the bottom edge; along the direction from the bottom edge to the top edge, the orthographic projection length of the at least two segments of the first curve on the plane containing the substrate gradually decreases.

10. The bulk acoustic resonator of claim 1, wherein, The side also includes: The second curve is parallel to the bottom edge and is located between two adjacent segments of the first curve.

11. The bulk acoustic resonator of claim 1, wherein, The reflective structure includes a cavity or a Bragg reflector layer.

12. The bulk acoustic resonator of claim 1, wherein, The reflective structure comprises first reflective gratings and second reflective gratings alternately stacked, wherein the first reflective gratings correspond to the side edges comprising first sub-curves, and the second reflective gratings correspond to the side edges comprising second sub-curves, and the first sub-curves and the second sub-curves are not parallel.

13. A filter, characterized by One or more bulk acoustic resonators as claimed in any of claims 1 to 12.

14. A multiplexer, characterized by One or more filters as claimed in claim 13.

15. A method of fabricating a bulk acoustic resonator, the method comprising: Comprising: providing a substrate; forming a sacrificial layer on the substrate; wherein the sacrificial layer comprises oppositely arranged bottom and top surfaces, and side surfaces connecting the bottom and top surfaces; a cross section of the sacrificial layer obtained by a plane perpendicular to a surface of the substrate comprises a bottom edge, a top edge, and two side edges, each of the side edges comprises at least two first curves, one of the first curves is connected with the bottom edge, and the other of the first curves is connected with the top edge, the at least two first curves are not parallel, and an angle between a tangent line of each point on each of the first curves and a plane where the bottom edge is located satisfies: greater than 0°, and less than or equal to 45°; forming a first electrode layer, a piezoelectric layer, and a second electrode layer in sequence on the sacrificial layer; removing the sacrificial layer to form a reflective structure comprising a cavity.

16. The method of claim 15, wherein The forming of the sacrificial layer on the substrate comprises: forming a sacrificial material layer covering the substrate; wherein the sacrificial material layer comprises a central region and an edge region surrounding the central region, and the edge region comprises at least two sub-regions arranged in sequence from the center to the edge; sequentially removing part of the sacrificial material layer in the at least two sub-regions to form a surface of the sacrificial material layer remaining in the at least two sub-regions as side surfaces of the sacrificial layer; wherein each of the sub-regions comprises a first curved surface, and the first curved surface is a first curve obtained by a plane perpendicular to a surface of the substrate.

17. The method of claim 16, wherein The sequentially removing part of the sacrificial material layer in the at least two sub-regions comprises: sequentially removing part of the sacrificial material layer in the at least two sub-regions by using an etching process; wherein different etching parameters are used for different sub-regions to make the first curves corresponding to the first curved surfaces of different sub-regions not parallel.

Images