Bulk acoustic wave resonator and method of manufacturing the same

Abstract

The application discloses a bulk acoustic wave resonator and a manufacturing method thereof. The bulk acoustic wave resonator comprises a substrate, a piezoelectric laminated structure on the substrate, the piezoelectric laminated structure comprising a lower electrode layer, a piezoelectric layer and an upper electrode layer which are sequentially laminated from bottom to top, and a reflective ring structure on the upper electrode layer and distributed along the edge of an effective resonance area of the resonator, the reflective ring structure comprising a ring-shaped supporting part and a ring-shaped mass adjusting part which are laminated from bottom to top, and the cross-sectional width of the ring-shaped supporting part is smaller than that of the ring-shaped mass adjusting part in the cross section perpendicular to the piezoelectric laminated direction. The application can effectively suppress the transverse wave of the resonator, improve the performance of the resonator, simplify the process of manufacturing resonators with different frequencies at the same time, and reduce the process cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor device manufacturing, in particular to a bulk acoustic wave resonator and a manufacturing method thereof. BACKGROUND

[0002] The basic structure of a bulk acoustic wave filter (BAW filter) is a "sandwich" structure of two metal electrodes sandwiching a piezoelectric thin film and an acoustic reflection structure (cavity or Bragg mirror) of a bottom substrate. When a high-frequency electrical signal is applied between the electrodes, a bulk acoustic wave propagating in the vertical direction is generated inside the piezoelectric material due to the piezoelectric effect. The acoustic wave of a suitable wavelength oscillates in the composite film layer to form a standing wave, and at this time, the signal resonates inside the material, and the equivalent impedance of the device reaches a maximum value.

[0003] The bulk acoustic wave filter can produce a transverse spurious resonance due to the following reasons: the Rayleigh surface wave is reflected back and forth at the edge of the electrode in the plane, the C-axis of the piezoelectric layer thin film is not perpendicular, the longitudinal wave is not 90° incident, and the transverse shear wave is reflected. This causes the transverse spurious resonance peak, resulting in a decrease in device performance. The common solutions in the industry are as follows:

[0004] 1. The working area is made into an irregular polygon (without parallel sides);

[0005] 2. Forming an electrode with a convex or concave structure frame.

[0006] The above two schemes can solve the problem of transverse spurious wave suppression to a certain extent, but the improvement of resonator performance is limited.

[0007] In addition, the scheme of manufacturing resonators of different frequencies in the bulk acoustic wave filter is as follows:

[0008] 1. The composite film layer (sandwich structure) of different resonators is made into different thicknesses. The advantages of this scheme are that the frequency adjustment has little effect on the performance of the resonator, and the disadvantages are that the process steps are many and the cost is high;

[0009] 2. A tuning pattern is made on the surface of the electrode, and the frequency is adjusted by the duty cycle of the tuning pattern to form resonators of different frequencies. The advantages of this scheme are that the process steps are few and the cost is low, and the disadvantages are that the performance of the resonator is affected. SUMMARY

[0010] The purpose of the present application is to provide a bulk acoustic wave resonator and a manufacturing method thereof, which can effectively suppress the transverse wave of the resonator, improve the performance of the resonator, and simplify the process of manufacturing resonators of different frequencies at the same time, and reduce the process cost.

[0011] In order to achieve the above purpose, in a first aspect, the present application provides a bulk acoustic wave resonator, comprising:

[0012] a substrate;

[0013] a piezoelectric laminated structure on the substrate, the piezoelectric laminated structure comprising a lower electrode layer, a piezoelectric layer and an upper electrode layer stacked in order from bottom to top;

[0014] a reflective ring structure on the upper electrode layer and distributed along an edge of an effective resonance region of the resonator, the reflective ring structure comprising a ring-shaped support portion and a ring-shaped mass adjustment portion stacked in order from bottom to top, the reflective ring structure in a cross section perpendicular to a direction of the piezoelectric laminated structure, a cross section width of the ring-shaped support portion being smaller than a cross section width of the ring-shaped mass adjustment portion.

[0015] In a second aspect, the present application provides a method for manufacturing a bulk acoustic wave resonator, comprising:

[0016] forming a piezoelectric laminated structure on the substrate, the piezoelectric laminated structure comprising a lower electrode layer, a piezoelectric layer and an upper electrode layer stacked in order from bottom to top;

[0017] forming a reflective ring structure on the upper electrode layer, the reflective ring structure being distributed along an edge of an effective resonance region of the resonator, the reflective ring structure comprising a ring-shaped support portion and a ring-shaped mass adjustment portion stacked in order from bottom to top, the reflective ring structure in a cross section perpendicular to a direction of the piezoelectric laminated structure, a cross section width of the ring-shaped support portion being smaller than a cross section width of the ring-shaped mass adjustment portion.

[0018] In a third aspect, the present application provides another method for manufacturing a bulk acoustic wave resonator, comprising:

[0019] forming a piezoelectric laminated structure on the substrate, the piezoelectric laminated structure comprising a lower electrode layer, a piezoelectric layer and an upper electrode layer stacked in order from bottom to top;

[0020] forming a plurality of reflective ring structures on the upper electrode layer, each of the reflective ring structures being distributed along an edge of an effective resonance region of the resonator, the reflective ring structure comprising a ring-shaped support portion and a ring-shaped mass adjustment portion stacked in order from bottom to top, the reflective ring structure in a cross section perpendicular to a direction of the piezoelectric laminated structure, a cross section width of the ring-shaped support portion being smaller than a cross section width of the ring-shaped mass adjustment portion, the cross section width of the ring-shaped mass adjustment portion of different reflective ring structures being different.

[0021] The present application has the following beneficial effects:

[0022] The body acoustic wave resonator structure of the present application is provided with a reflecting ring structure at the edge of the working area of the piezoelectric laminated structure, the reflecting ring structure comprises a ring-shaped supporting part and a ring-shaped mass adjusting part stacked from bottom to top, and the cross-sectional width of the ring-shaped supporting part is smaller than that of the ring-shaped mass adjusting part in the cross section perpendicular to the piezoelectric laminated direction, that is, the reflecting ring structure has the feature of being wide at the top and narrow at the bottom. The reflecting ring structure can not only realize the reflection suppression of the transverse wave at the edge of the working area of the resonator, but also can play the function of mass load due to the structure of being wide at the top and narrow at the bottom, which can concentrate the greater weight in the narrower area. Different mass loads can be realized by adjusting the width of the upper ring-shaped mass adjusting part, so as to realize the frequency adjustment of the resonator.

[0023] Further, the body acoustic wave resonator manufacturing method of the present application can adjust the weight of the mass load by controlling the width of the upper ring-shaped mass adjusting part of the reflecting ring of different resonators in one photoetching process, so as to manufacture resonators with different frequencies. The resonators with different frequencies can also be manufactured simultaneously in one photoetching process, which has the advantages of fewer process steps and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.

[0025] Figure 1 FIG. 1 is a cross-sectional structure schematic diagram of a body acoustic wave resonator according to Embodiment 1 of the present application.

[0026] Figure 2 FIG. 2 is a working area top view of the body acoustic wave resonator according to Embodiment 1 of the present application.

[0027] Figure 3 FIG. 3 is another cross-sectional structure schematic diagram of a body acoustic wave resonator according to Embodiment 1 of the present application.

[0028] Figure 4 FIG. 4 is a device structure schematic diagram corresponding to each step of the manufacturing method of a body acoustic wave resonator according to Embodiment 2 of the present application.

[0029] Figure 5 FIG. 5 is a device structure schematic diagram corresponding to each step of the manufacturing method of a body acoustic wave resonator according to Embodiment 3 of the present application.

[0030] Figure 6 FIG. 6 is a device structure schematic diagram corresponding to each step of the manufacturing method of a body acoustic wave resonator according to Embodiment 4 of the present application.

[0031] Figure 7 Figure 1 is a device structure diagram corresponding to each step of a method for manufacturing a bulk acoustic wave resonator according to Embodiment 5 of the present application. DETAILED DESCRIPTION

[0032] The filter chip packaging structure and wafer level packaging method of the present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present application will be more apparent from the following description and drawings, however, it should be noted that the technical solutions of the present application can be implemented in various different forms and are not limited to the specific embodiments described herein. The accompanying drawings are all in a very simplified form and use non-precise proportions, only for the purpose of facilitating and clarifying the purpose of assisting in the description of the embodiments of the present application.

[0033] The terms "first", "second", and the like in the description and in the claims are used to distinguish between like elements, and are not necessarily used to describe a particular sequential or chronological order. It is to be understood that, where appropriate, the terms so used can be interchangeable, for example, the embodiments of the application described herein can operate in other sequences than the one described or illustrated herein and / or with other components than the ones described or illustrated herein. Similarly, if a method is described herein, it is to be understood that the steps of the method can be performed in a different order than the one described or illustrated herein, and / or some of the steps described herein can be omitted and / or some other steps not described herein can be added to the method. Where components of a figure are identical to components of other figures, although these components can be easily recognized in all the figures, the description will not label all identical components with the same reference numerals in each figure for the sake of clarity of the description of the figures.

[0034] Embodiment 1

[0035] As shown in Figure 1 the present embodiment provides a bulk acoustic wave resonator, comprising:

[0036] a substrate 1, in the present embodiment, the front surface of the substrate 1 has a cavity 7, the piezoelectric layer structure seals the cavity 7, and the resonator working area is located above the cavity 7;

[0037] a piezoelectric layer structure located on the substrate 1, the piezoelectric layer structure comprises a lower electrode 2 layer, a piezoelectric layer 3, and an upper electrode 4 layer stacked in order from bottom to top;

[0038] a reflective ring structure located on the upper electrode 4 layer and distributed along the edge of the effective resonant area of the resonator, the reflective ring structure comprises a ring-shaped support part 5 and a ring-shaped mass adjustment part 6 stacked from bottom to top, and in a cross section perpendicular to the piezoelectric layer direction, the cross-sectional width of the ring-shaped support part 5 is smaller than the cross-sectional width of the ring-shaped mass adjustment part 6.

[0039] In the embodiment, the ratio of the cross-sectional width of the annular support part 5 to the cross-sectional width of the annular mass adjusting part 6 in the cross section perpendicular to the piezoelectric layer stack direction is preferably in the range of 1:2 to 1:5. In the implementation process, the mass load of the reflective ring structure can be adjusted by adjusting the width of the mass adjusting part, and the frequency range of the resonator can be controlled. For example, when the cross-sectional width of the annular mass adjusting part 6 is small, the mass load of the reflective ring structure is small, the frequency of the resonator is high, and the resonator is a high-frequency resonator. When the cross-sectional width of the annular mass adjusting part 6 is large, the mass load of the reflective ring structure is large, the frequency of the resonator is low, and the resonator is a low-frequency resonator.

[0040] In the embodiment, the annular support part 5 and the annular mass adjusting part 6 are made of the same or different materials. The annular support part 5 and the annular mass adjusting part 6 can be made of metal or semiconductor materials.

[0041] As shown in Figure 2 In the embodiment, the projection of the reflective ring structure on the piezoelectric layer 3 is an irregular polygon, and any two sides of the polygon are not parallel. That is, the overall projection shape of the reflective ring structure on the piezoelectric layer 3 is the same as the working area shape.

[0042] In other embodiments, as shown in Figure 3 The substrate 1 can also have a Bragg reflector 8, and the resonator working area is located above the Bragg reflector 8.

[0043] In the bulk acoustic wave resonator of the embodiment, the reflective ring structure has the characteristics of being wide at the top and narrow at the bottom. The reflective ring structure not only can realize reflection suppression of the transverse wave at the edge of the working area of the resonator, but also can play the role of mass load due to the structure of being wide at the top and narrow at the bottom, which concentrates the larger weight in the narrower area. Different mass loads can be realized by adjusting the width of the upper annular mass adjusting part 6, so as to adjust the frequency of the resonator.

[0044] Embodiment 2

[0045] As shown in Figure 4 The embodiment provides a manufacturing method of a bulk acoustic wave resonator, which comprises the following steps:

[0046] S1: forming a piezoelectric layer stack structure on the substrate 1, wherein the piezoelectric layer stack structure comprises a lower electrode 2 layer, a piezoelectric layer 3, and an upper electrode 4 layer which are sequentially stacked from bottom to top;

[0047] In this step, the lower electrode 2 layer, the piezoelectric layer 3, and the upper electrode 4 layer can be sequentially formed on the substrate 1 by a deposition process.

[0048] In this embodiment, the substrate 1 can be any suitable substrate known to those skilled in the art, for example, it can be at least one of the following materials: silicon (Si), germanium (Ge), lithium niobate (LiNbO3), lithium tantalate (LiTaO3), silicon-germanium (SiGe), silicon-carbon (SiC), silicon-germanium-carbon (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP) or other III / V compound semiconductors, including multilayer structures formed by these semiconductors, etc., or silicon-on-insulator (SOI), silicon-on-silicon-on-insulator (SSOI), silicon-germanium-on-silicon-on-insulator (S-SiGeOI), silicon-germanium-on-insulator (SiGeOI) and germanium-on-insulator (GeOI), or double side polished wafers (DSP), ceramic substrates such as alumina, quartz, sapphire or glass substrates, etc. In this embodiment, the substrate 1 is a silicon substrate 1.

[0049] The front surface of the substrate 1 has a cavity 7, and the piezoelectric layer structure is formed to enclose the cavity 7. In the process, the piezoelectric layer structure can be formed after depositing a sacrificial layer in the cavity 7 on the front surface of the substrate 1, and the sacrificial layer in the cavity 7 can be released after the reflective ring structure is subsequently formed. The projection of the cavity 7 on the piezoelectric layer 3 is preferably an irregular pentagon with non-parallel sides, i.e. the shape of the resonator operating area, which is consistent with the projection shape of the subsequently formed reflective ring structure on the piezoelectric layer 3. In other embodiments, the substrate 1 can also have a Bragg mirror 8 (formed by alternating layers of low and high acoustic velocity materials) in it, and the piezoelectric layer structure can be directly formed on the substrate 1.

[0050] The materials of the upper electrode 4 layer and the lower electrode 2 layer can be any suitable conductive material known to those skilled in the art, which can be a metal material with conductive properties, for example, made of one of the following metals: molybdenum (Mo), aluminum (Al), copper (Cu), tungsten (W), tantalum (Ta), platinum (Pt), ruthenium (Ru), rhodium (Rh), iridium (Ir), chromium (Cr), titanium (Ti), gold (Au), osmium (Os), rhenium (Re), palladium (Pd), etc., or made of a stack of the above-mentioned metals. The upper and lower electrodes 2 layers can be formed by physical vapor deposition such as magnetron sputtering, evaporation, or chemical vapor deposition, physical vapor deposition or atomic layer deposition, etc.

[0051] The material of the piezoelectric layer 3 can use aluminum nitride (AIN), zinc oxide (ZnO), lead zirconate titanate (PZT), lithium niobate (LiNbO3), quartz (Quartz), potassium niobate (KNbO3), or lithium tantalate (LiTaO3), and the like piezoelectric materials having a wurtzite crystal structure and combinations thereof. When the piezoelectric layer 3 includes aluminum nitride (AIN), the piezoelectric layer 3 can further include at least one of rare earth metals such as scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La). In addition, when the piezoelectric layer 3 includes aluminum nitride (AIN), the piezoelectric layer 3 can further include at least one of transition metals such as zirconium (Zr), titanium (Ti), manganese (Mn), and hafnium (Hf). The piezoelectric layer 3 can be deposited using any suitable method known to those skilled in the art such as chemical vapor deposition, physical vapor deposition, or atomic layer deposition. In the present embodiment, the piezoelectric layer 3 is made of aluminum nitride (AIN).

[0052] S2: forming a reflective ring structure on the upper electrode 4 layer, the reflective ring structure being distributed along the edge of the working area of the resonator, the reflective ring structure including, from bottom to top, a ring-shaped support portion 5 and a ring-shaped mass adjustment portion 6, the reflective ring structure in a cross-section perpendicular to the piezoelectric layer direction, the cross-sectional width of the ring-shaped support portion 5 being smaller than the cross-sectional width of the ring-shaped mass adjustment portion 6.

[0053] Reference Figure 4 In the present embodiment, forming a reflective ring structure on the upper electrode 4 layer includes:

[0054] S201: forming a sacrificial layer 9 on the upper electrode 4 layer;

[0055] The material of the sacrificial layer 9 can be silicon dioxide (SiO2), silicon nitride (Si3N4), aluminum oxide (Al2O3), and aluminum nitride (AIN), carbon, germanium, silicon, and the like materials that can be bonded with a silicon wafer. The sacrificial layer 9 can be formed by chemical vapor deposition, magnetron sputtering, or evaporation, and the like.

[0056] S202: patterning the sacrificial layer 9 to form a ring-shaped groove 10 distributed along the edge of the working area on the sacrificial layer 9, the bottom of the ring-shaped groove 10 exposing the surface of the upper electrode 4 layer;

[0057] The sacrificial layer 9 can be patterned by a photolithography process, specifically including forming a patterned photoresist on the sacrificial layer 9, and then etching the sacrificial layer 9 by a dry etching process to form a ring-shaped groove 10, the projection of the ring-shaped groove 10 on the piezoelectric layer 3 being a pentagon with any two sides not parallel.

[0058] S203: forming a first material layer 11 on the sacrificial layer 9, the first material layer 11 filling the annular groove 10 and covering the surface of the sacrificial layer 9, the thickness of the first material layer 11 being greater than the thickness of the sacrificial layer 9, the first material layer 11 in the annular groove 10 forming the annular support part 5;

[0059] The thickness of the first material layer 11 being greater than the thickness of the sacrificial layer 9 can ensure that the first material layer 11 filled in the groove and the first material layer 11 on the sacrificial layer 9 are connected together, and ensure that the annular mass adjustment part 6 formed by etching the first material layer 11 is an integral structure with the annular support part 5 in the groove.

[0060] The material of the first material layer 11 can be a dielectric material or a metal material, the metal material including one or more of Mo, W, Al, Cu, Au, Pt, Ti, and the dielectric material including one or more of SiO2, SiN, and AlN. The first material layer 11 can be formed by chemical vapor deposition, magnetron sputtering, or evaporation.

[0061] S204: forming a first photoresist layer on the first material layer 11; patterning the first photoresist layer to form a first annular photoresist mask 12 corresponding to the annular groove 10 on the first material layer 11, the annular groove 10 being located in the coverage range of the first annular photoresist mask 12, and the width of the first annular photoresist mask 12 being greater than the width of the annular groove 10;

[0062] This step forms the first annular photoresist mask 12 by exposing and developing the first photoresist layer. The first annular photoresist mask 12 is used to define the width of the upper annular mass adjustment part 6 of the reflective ring structure. By controlling the width of the first annular photoresist mask 12, the width of the annular mass adjustment part 6 formed subsequently is controlled, and then the mass load of the reflective ring structure is controlled, so that the resonator produced reaches the required frequency.

[0063] S205: etching and removing the first material layer 11 outside the coverage range of the first annular photoresist mask 12 to form the annular mass adjustment part 6 on the annular support part 5;

[0064] By forming the annular photoresist mask with a width greater than the annular groove 10 above the annular support part 5 in the annular groove 10, and then etching the first material layer 11 using the annular photoresist mask, the annular mass adjustment part 6 connected to the annular support part 5 and wider than the annular support part 5 can be formed above the annular support part 5 in the groove, so as to form the reflective ring structure with the upper part being wide and the lower part being narrow.

[0065] S206: removing the first annular photoresist mask 12;

[0066] The first annular photoresist mask 12 can be removed by a dry or wet stripping process.

[0067] S207: removing the sacrificial layer 9.

[0068] The sacrificial layer 9 on the upper electrode 4 layer can be removed by a wet etching process. In addition, the sacrificial layer filled in the front cavity 7 of the substrate 1 can also be removed at this step, and the release hole can be formed on the piezoelectric layer structure by a wet process.

[0069] The method of the embodiment can adjust the weight of the mass load by controlling the width of the upper annular mass adjustment part 6 of the reflection ring of different resonators in one photoresist process, so as to manufacture resonators with different frequencies.

[0070] Embodiment 3

[0071] The embodiment provides a method for manufacturing a bulk acoustic wave resonator, and the difference between the embodiment and the embodiment 2 is that the method for forming the reflection ring structure in step S2 is different, as shown in the following table: Figure 5 The method of the embodiment includes the following steps:

[0072] S1: forming a piezoelectric layer structure on a substrate 1, wherein the piezoelectric layer structure includes a lower electrode 2 layer, a piezoelectric layer 3 and an upper electrode 4 layer which are sequentially stacked from bottom to top.

[0073] The film layer materials and the film layer manufacturing processes involved in this step are referred to the embodiment 2, and will not be described here.

[0074] S2: forming a reflection ring structure on the upper electrode 4 layer, wherein the reflection ring structure is distributed along the edge of the working area of the resonator, the reflection ring structure includes an annular support part 5 and an annular mass adjustment part 6 which are sequentially stacked from bottom to top, and the cross-sectional width of the annular support part 5 is smaller than the cross-sectional width of the annular mass adjustment part 6 in the cross section perpendicular to the piezoelectric layer direction.

[0075] Referring to Figure 5 , in the embodiment, the method for forming the reflection ring structure on the upper electrode 4 layer includes the following steps:

[0076] S211: forming a second material layer 13 on the upper electrode 4 layer; and forming a third material layer 14 on the second material layer 13.

[0077] The material of the second material layer 13 is a metal material, the material of the third material layer 14 is a dielectric material, the metal material includes one or more of Mo, W, Al, Cu, Au, Pt and Ti, and the dielectric material includes one or more of SiO2, SiN and AlN.

[0078] S212: Forming a second photoresist layer on the third material layer 14; patterning the second photoresist layer to form a second annular photoresist mask 15 distributed along the edge of the working area;

[0079] The second annular photoresist mask 15 formed in this step is used to define the width of the upper annular mass adjusting part 6 of the reflective ring structure.

[0080] S213: Etching to remove the third material layer 14 and the second material layer 13 outside the coverage of the second annular photoresist mask 15, and the remaining third material layer 14 and the second material layer 13 form an upper and lower stacked annular structure 16 on the upper electrode 4 layer, and the third material layer 14 located in the upper layer in the annular structure 16 forms the annular mass adjusting part 6;

[0081] S214: Removing the second annular photoresist mask 15;

[0082] The formation and removal of the second annular photoresist mask 15 are consistent with the related processes of the first annular photoresist mask 12 in Embodiment 2, which will not be repeated here.

[0083] S215: Lateral etching is performed on the sidewall of the second material layer 13 located in the lower layer in the annular structure 16 to reduce the width of the second material layer 13 to form the annular support part 5;

[0084] In this step, wet metal etching process can be used to perform lateral etching on the sidewall of the second material layer 13 to reduce the width of the bottom of the annular structure 16, and finally form a reflective ring structure with a wide upper part and a narrow lower part.

[0085] Embodiment 4

[0086] This embodiment provides a method for manufacturing a bulk acoustic wave resonator. The main difference between this embodiment and Embodiment 2 is that the method of this embodiment simultaneously forms multiple reflective ring structures with different top layer widths on a substrate 1 (wafer) to achieve different resonators with different mass loads, thereby simultaneously manufacturing multiple resonators with different frequencies. The processes used in each step and the materials of each film layer are the same as those in Embodiment 2.

[0087] As shown in FIG. 1, Figure 6 a method for manufacturing a bulk acoustic wave resonator according to an embodiment of the present application includes:

[0088] S01: Forming a piezoelectric layer structure on a substrate 1, the piezoelectric layer structure includes a lower electrode 2 layer, a piezoelectric layer 3, and an upper electrode 4 layer stacked in order from bottom to top;

[0089] S02: forming a plurality of spaced reflective ring structures on the upper electrode 4 layer, each of the reflective ring structures is distributed along the edge of the working area of one resonator, the reflective ring structure comprises a ring-shaped support part 5 and a ring-shaped mass adjustment part 6 stacked from bottom to top, the cross-sectional width of the ring-shaped support part 5 is smaller than the cross-sectional width of the ring-shaped mass adjustment part 6 in the cross-section perpendicular to the direction of the piezoelectric layer 3, and the cross-sectional widths of the ring-shaped mass adjustment parts 6 of different reflective ring structures are different in the cross-section perpendicular to the direction of the piezoelectric layer 3.

[0090] Reference Figure 6 The step S02 described above, forming a plurality of spaced reflective ring structures on the upper electrode 4 layer, specifically comprises:

[0091] S301: forming a sacrificial layer 9 on the upper electrode 4 layer;

[0092] S302: patterning the sacrificial layer 9 to form a plurality of ring-shaped grooves 10 on the sacrificial layer 9, each of the ring-shaped grooves 10 is distributed along the edge of the working area of one resonator, and the bottom of the ring-shaped groove 10 exposes the surface of the upper electrode 4 layer;

[0093] S303: forming a first material layer 11 on the sacrificial layer 9, the first material layer 11 fills the ring-shaped grooves 10 and covers the surface of the sacrificial layer 9, the thickness of the first material layer 11 is greater than the thickness of the sacrificial layer 9, and the first material layer 11 in each ring-shaped groove 10 forms a ring-shaped support part 5 of a reflective ring;

[0094] S304: forming a first photoresist layer on the first material layer 11;

[0095] S305: patterning the first photoresist layer to form a plurality of first ring-shaped photoresist masks 12 on the first material layer 11, each of the first ring-shaped photoresist masks 12 corresponds to one of the ring-shaped grooves 10, and the cross-sectional widths of different first ring-shaped photoresist masks 12 are different in the cross-section perpendicular to the direction of the piezoelectric layer 3, each ring-shaped groove 10 is located in the coverage range of one first ring-shaped photoresist mask 12, and the cross-sectional width of each first ring-shaped photoresist mask 12 is greater than the cross-sectional width of the corresponding ring-shaped groove 10 in the cross-section perpendicular to the direction of the piezoelectric layer 3;

[0096] S306: etching to remove the first material layer 11 outside the coverage range of the plurality of first ring-shaped photoresist masks 12, and respectively forming a ring-shaped mass adjustment part 6 on each ring-shaped support part 5;

[0097] S307: removing the first ring-shaped photoresist mask 12;

[0098] S308: removing the sacrificial layer 9.

[0099] In this embodiment, the front surface of the substrate 1 has a plurality of cavities 7, and the piezoelectric layer structure seals the cavities 7, and each of the reflective ring structures is located above one of the cavities 7. In other embodiments, the substrate 1 has a plurality of Bragg reflectors 8, and each of the reflective ring structures is located above one of the Bragg reflectors 8.

[0100] The method of this embodiment can use one photolithography process to manufacture reflective ring structures with different top layer widths, as shown in FIG. 1B. Figure 6 As shown in FIG. 1B, the top layer ring-shaped mass adjustment parts in the reflective ring structures corresponding to the two resonators have different widths (W1 < W2), and different mass loads are achieved, thereby achieving the simultaneous manufacture of resonators with different frequencies in one photolithography process, which has the advantages of fewer process steps and low cost.

[0101] Embodiment 5

[0102] This embodiment provides a method for manufacturing a bulk acoustic wave resonator, and the difference between this embodiment and embodiment 4 mainly lies in the different way of manufacturing a plurality of reflective ring structures in step S02. The processes used in each step and the materials of each film layer are the same as those in embodiment 3.

[0103] As shown in FIG. 1B, the method for manufacturing a bulk acoustic wave resonator of this embodiment includes: Figure 7

[0104] S01: Forming a piezoelectric layer structure on a substrate 1, which includes a lower electrode 2 layer, a piezoelectric layer 3, and an upper electrode 4 layer stacked in order from bottom to top;

[0105] S02: Forming a plurality of spaced reflective ring structures on the upper electrode 4 layer, each of which is distributed along the edge of the working area of one resonator, and each of which includes a ring-shaped support part 5 and a ring-shaped mass adjustment part 6 stacked in order from bottom to top. In a cross-section perpendicular to the piezoelectric layer direction, the cross-sectional width of the ring-shaped support part 5 is smaller than that of the ring-shaped mass adjustment part 6, and the cross-sectional widths of the ring-shaped mass adjustment parts 6 of different reflective ring structures are different in a cross-section perpendicular to the piezoelectric layer 3 direction.

[0106] Referring to FIG. 1B, in step S02 of this embodiment, forming a plurality of spaced reflective ring structures on the upper electrode 4 layer specifically includes: Figure 7 S401: Forming a second material layer 13 on the upper electrode 4 layer; and forming a third material layer 14 on the second material layer 13;

[0107]

[0108] ​​S402: Forming a second photoresist layer on the third material layer 14; patterning the second photoresist layer to form a plurality of second ring-shaped photoresist masks 15 on the third material layer 14, different second ring-shaped photoresist masks 15 have different cross-sectional widths perpendicular to the piezoelectric layer 3, and each second ring-shaped photoresist mask 15 is distributed along the edge of the working area of a resonator;

[0109] S403: Etching to remove the third material layer 14 and the second material layer 13 outside the coverage of the plurality of second ring-shaped photoresist masks 15, and the remaining third material layer 14 and the second material layer 13 form a plurality of upper and lower stacked ring-shaped structures 16 on the upper electrode 4, and the third material layer 14 in the upper layer of the plurality of ring-shaped structures 16 forms ring-shaped mass adjustment parts 6 with different widths respectively;

[0110] S404: Removing the second ring-shaped photoresist mask 15;

[0111] S405: Lateral etching the sidewall of the second material layer 13 in the lower layer of the plurality of ring-shaped structures 16 to reduce the width of the second material layer 13 to form a plurality of ring-shaped support parts 5.

[0112] The method of the embodiment also uses one photoetching process to manufacture the top layer of the reflective ring structure with different widths, as shown in Figure 7 The width of the top layer of the ring-shaped mass adjustment part in the reflective ring structure corresponding to the two resonators is different (W1 < W2), and different mass loads are achieved, thereby achieving the simultaneous manufacture of resonators with different frequencies in one photoetching process, and having the advantages of fewer process steps and low cost.

[0113] It should be noted that each embodiment in the present specification is described in a related manner, and the same and similar parts of each embodiment can be referred to each other, and each embodiment mainly describes the difference from other embodiments. In particular, for structural embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the related parts can be referred to the part of the method embodiment.

[0114] The above description is only a description of the preferred embodiments of the present application, and does not limit the scope of the present application in any way, and any modification or modification of the above-mentioned disclosure by a person skilled in the art falls within the protection scope of the claims.

Claims

1. A method of fabricating a bulk acoustic resonator, comprising: The method comprises the following steps: forming a piezoelectric layer structure on a substrate, the piezoelectric layer structure comprising a lower electrode layer, a piezoelectric layer and an upper electrode layer stacked in order from bottom to top; forming a reflective ring structure on the upper electrode layer, the reflective ring structure being distributed along the edge of an operating area of a resonator, the reflective ring structure comprising a ring-shaped support portion and a ring-shaped mass adjustment portion stacked in order from bottom to top, the cross-sectional width of the ring-shaped support portion being smaller than the cross-sectional width of the ring-shaped mass adjustment portion in a cross section perpendicular to the piezoelectric layer direction; forming a reflective ring structure on the upper electrode layer comprises: forming a second material layer on the upper electrode layer; forming a third material layer on the second material layer; forming a second photoresist layer on the third material layer; patterning the second photoresist layer to form a second ring-shaped photoresist mask distributed along the edge of the operating area; etching to remove the third material layer and the second material layer outside the coverage of the second ring-shaped photoresist mask, the remaining third material layer and the second material layer forming an upper and lower stacked ring-shaped structure on the upper electrode layer, the third material layer located in the upper layer in the ring-shaped structure forming the ring-shaped mass adjustment portion; removing the second ring-shaped photoresist mask; performing lateral etching on the sidewall of the second material layer located in the lower layer in the ring-shaped structure to reduce the width of the second material layer to form the ring-shaped support portion.

2. The method of claim 1, wherein The material of the second material layer is a metal material, and the material of the third material layer is a dielectric material.

3. The method of claim 2, wherein The method for manufacturing a bulk acoustic wave resonator comprises performing lateral etching on the sidewall of the second material layer by a wet etching process.

4. The method of claim 1, wherein The ratio of the cross-sectional width of the ring-shaped support portion to the cross-sectional width of the ring-shaped mass adjustment portion in a cross section perpendicular to the piezoelectric layer direction is in the range of 1:2 to 1:

5.

5. The method of claim 1, wherein The projection of the reflective ring structure on the piezoelectric layer is an irregular polygon, and any two sides of the polygon are not parallel.

6. The method of claim 1, wherein The front surface of the substrate has a cavity, and the piezoelectric layer structure seals the cavity, or the substrate has a Bragg reflector.

7. A method of fabricating a bulk acoustic resonator, the method comprising: The method comprises the following steps: forming a piezoelectric layer structure on a substrate, the piezoelectric layer structure comprising a lower electrode layer, a piezoelectric layer and an upper electrode layer stacked in order from bottom to top; forming a plurality of reflective ring structures distributed at intervals on the upper electrode layer, each reflective ring structure being distributed along the edge of an operating area of a resonator, the reflective ring structure comprising a ring-shaped support portion and a ring-shaped mass adjustment portion stacked in order from bottom to top, the cross-sectional width of the ring-shaped support portion being smaller than the cross-sectional width of the ring-shaped mass adjustment portion in a cross section perpendicular to the piezoelectric layer direction, and the cross-sectional width of the ring-shaped mass adjustment portion of different reflective ring structures being different in a cross section perpendicular to the piezoelectric layer direction; forming a plurality of reflective ring structures distributed at intervals on the upper electrode layer comprises: forming a second material layer on the upper electrode layer; forming a third material layer on the second material layer; forming a second photoresist layer on the third material layer; patterning the second photoresist layer to form a second ring-shaped photoresist mask distributed along the edge of the operating area; forming a plurality of spaced second ring-shaped photoresist masks on the third material layer, different second ring-shaped photoresist masks having different cross-sectional widths perpendicular to the piezoelectric layer, each second ring-shaped photoresist mask being distributed along the edge of the operating region of a resonator; etching and removing the third material layer and the second material layer outside the coverage of the plurality of second ring-shaped photoresist masks, the remaining third material layer and the second material layer forming a plurality of upper and lower stacked ring-shaped structures on the upper electrode layer, the third material layer in the upper layer of the plurality of ring-shaped structures forming ring-shaped mass adjustment portions with different widths respectively; removing the second ring-shaped photoresist masks; performing lateral etching on the sidewalls of the second material layer in the lower layer of the plurality of ring-shaped structures to reduce the width of the second material layer, forming a plurality of ring-shaped support portions.

8. The method of claim 7, wherein, The front surface of the substrate has a plurality of cavities, and the piezoelectric layer structure seals the cavities, and each of the reflective ring structures is located above a cavity; or, the substrate has a plurality of Bragg reflectors, and each of the reflective ring structures is located above a Bragg reflector.

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