Solid-state assembly type bulk acoustic wave resonator and preparation method thereof

Abstract

The present application discloses a solid-state assembly type bulk acoustic wave resonator and a preparation method thereof, wherein the solid-state assembly type bulk acoustic wave resonator comprises a substrate, a Bragg reflection structure stacked on the substrate in sequence, a first electrode layer, a piezoelectric layer, and a second electrode layer, the Bragg reflection structure comprises a non-conductive reflection structure and a conductive reflection structure, the non-conductive reflection structure and the conductive reflection structure both comprise a high acoustic impedance layer and a low acoustic impedance layer stacked alternately, the material of the high acoustic impedance layer and the low acoustic impedance layer of the non-conductive reflection structure are both non-conductive materials, and the material of at least one of the high acoustic impedance layer and the low acoustic impedance layer of the conductive reflection structure is a conductive material. The present application can effectively prevent sound waves from being transmitted to the substrate through the Bragg reflection structure by arranging a non-conductive reflection structure between the substrate and the first electrode layer. Since the non-conductive reflection structure is made of non-conductive materials, it is not necessary to perform patterning on it, which can reduce the number of etching times and the process difficulty.

Description

Technical Field

[0001] The present invention relates to the technical field of resonators, in particular to a solid-state assembled bulk acoustic wave resonator and a preparation method thereof. Background Art

[0002] BAW resonator (Bulk Acoustic Wave Resonator, BAW) is a resonant device based on the propagation of bulk acoustic waves. It has the advantages of high quality factor, high frequency stability and low loss, and has been widely used in wireless communications, digital television, computers, bulk acoustic wave filters, etc. The working principle of BAW resonator is to use the piezoelectric effect of piezoelectric materials to convert electrical energy into mechanical energy, generate bulk acoustic waves, and form resonance in the resonant cavity, thereby realizing the selection and control of frequency.

[0003] There are two mainstream bulk acoustic wave resonators, one is the film bulk acoustic wave resonator (FBAR), and the other is the solid-mounted bulk acoustic wave resonator (SMR). Among them, FBAR consists of upper and lower electrodes and a piezoelectric film sandwiched in the middle. The resonant cavity of FBAR is formed by an air gap or a vacuum gap under the piezoelectric film. This structure can effectively reduce the propagation loss of sound waves, but the preparation process is relatively cumbersome, the yield rate is low, and the contact surface between the FBAR device and the substrate is small, and the heat accumulation effect generated is relatively serious, which is difficult to apply to some high-power application scenarios. The main difference between SMR and FBAR lies in the formation of the resonant cavity. SMR uses high acoustic impedance film materials (such as tungsten) and low acoustic impedance film materials (such as silicon dioxide) to alternately form a Bragg acoustic wave reflection structure to replace the air gap or vacuum gap in FBAR. SMR uses a Bragg reflection structure to replace the air gap or vacuum gap in FBAR. This structure can better resist the influence of the external environment, such as temperature changes, mechanical stress, etc., thereby improving the stability and reliability of the resonator. SMRs are generally able to handle higher power, which gives them an advantage over FBARs in some applications that require processing high-power signals.

[0004] The performance of SMR, especially the resonator quality factor (Quality Factor, Q), is closely related to the structural design of its Bragg acoustic wave reflection layer. To optimize the acoustic wave reflection layer of SMR, high acoustic impedance and low acoustic impedance materials need to be carefully selected. High acoustic impedance materials usually have a larger density and elastic modulus, such as tungsten, titanium tungsten alloy, molybdenum, aluminum nitride, etc.; low acoustic impedance materials usually have a smaller density and elastic modulus, such as silicon dioxide, silicon nitride, styrene, etc. In addition, the optimal number of reflection layers is determined through theoretical calculations and simulations. Generally speaking, increasing the number of layers can improve the reflection efficiency, but it will also increase the difficulty and cost of manufacturing. Summary of the invention

[0005] In view of the above problems, an object of the present invention is to provide a solid-state assembly type bulk acoustic wave resonator and a method for preparing the same.

[0006] According to a first aspect of the present invention, there is provided a bulk acoustic wave resonator, comprising a substrate, a Bragg reflection structure sequentially stacked on the substrate, a first electrode layer, a piezoelectric layer, and a second electrode layer:

[0007] The Bragg reflection structure includes a non-conductive reflection structure and a conductive reflection structure, and both the non-conductive reflection structure and the conductive reflection structure include alternately stacked high acoustic impedance layers and low acoustic impedance layers, and the materials of the high acoustic impedance layer and the low acoustic impedance layer of the non-conductive reflection structure are both non-conductive materials, and the material of at least one of the high acoustic impedance layer and the low acoustic impedance layer of the conductive reflection structure is conductive material.

[0008] Optionally, the non-conductive reflective structure is located on the substrate and completely covers the substrate, the non-conductive reflective structure is a first periodic structure, each first period includes a first high acoustic impedance layer and a first low acoustic impedance layer, and the number of first periods is at least 1.

[0009] Optionally, the conductive reflective structure is located between the non-conductive reflective structure and the first electrode layer and partially covers the non-conductive reflective structure, the conductive reflective structure is a second periodic structure, each second period includes a second high acoustic impedance layer and a second low acoustic impedance layer, and the number of second periods is at least 1.

[0010] Optionally, the period number of the Bragg reflection structure is at least 3.

[0011] Optionally, the material of the first high acoustic impedance layer is at least one of aluminum nitride, tantalum pentoxide, hafnium oxide, aluminum oxide, silicon carbide, boron nitride, zirconium oxide, titanium oxide, and tungsten oxide; the material of the first low acoustic impedance layer is at least one of silicon dioxide, silicon nitride, magnesium oxide, nanoporous mixture, aerogel, dry gel or polymer material.

[0012] Optionally, the material of the second high acoustic impedance layer is at least one of tungsten, titanium tungsten, molybdenum, platinum, ruthenium, iridium, hafnium, tantalum, nickel, chromium, cobalt, zirconium carbide, cobalt oxide, aluminum nitride, tantalum pentoxide, hafnium oxide, aluminum oxide, silicon carbide, boron nitride, zirconium oxide, titanium oxide, and tungsten oxide; the material of the second low acoustic impedance layer is at least one of aluminum, magnesium, silicon dioxide, silicon nitride, magnesium oxide, nanoporous mixture, aerogel, dry gel or polymer material.

[0013] Optionally, when the second high acoustic impedance layer and the second low acoustic impedance layer are both made of conductive materials, the second high acoustic impedance layer and the second low acoustic impedance layer partially cover the non-conductive reflective structure; when the material of the second high acoustic impedance layer is conductive material and the material of the second low acoustic impedance layer is non-conductive material, the second low acoustic impedance layer completely covers the non-conductive reflective structure, and the second high acoustic impedance layer partially covers the non-conductive reflective structure; when the material of the second high acoustic impedance layer is non-conductive material and the material of the second low acoustic impedance layer is conductive material, the second high acoustic impedance layer completely covers the non-conductive reflective structure, and the second low acoustic impedance layer partially covers the non-conductive reflective structure.

[0014] According to a second aspect of the present invention, there is provided a method for preparing the solid-state assembled bulk acoustic wave resonator described above, comprising: forming a Bragg reflection structure on a substrate; sequentially forming a first electrode layer, a piezoelectric layer, and a second electrode layer on the Bragg reflection structure; forming the Bragg reflection structure on the substrate comprises: alternately depositing high acoustic impedance layers and low acoustic impedance layers on the substrate to form a non-conductive reflection structure; alternately depositing high acoustic impedance layers and low acoustic impedance layers on the non-conductive reflection structure and patterning them to form a conductive reflection structure; the materials of the high acoustic impedance layer and the low acoustic impedance layer of the non-conductive reflection structure are both non-conductive materials, and the material of at least one of the high acoustic impedance layer and the low acoustic impedance layer of the conductive reflection structure is conductive material.

[0015] Optionally, both the high acoustic impedance layer and the low acoustic impedance layer of the conductive reflective structure are patterned to form a conductive reflective structure, wherein the conductive reflective structure partially covers the non-conductive reflective structure.

[0016] Optionally, one layer of the conductive reflective structure is patterned, and the other layer is not patterned to form a conductive reflective structure, wherein one layer partially covers the non-conductive reflective structure, and the other layer completely covers the non-conductive reflective structure;

[0017] The material of one layer is a conductive material, and the material of the other layer is a non-conductive material.

[0018] Beneficial Effects

[0019] According to the solid-state assembled bulk acoustic wave resonator and the preparation method thereof of the embodiments of the present invention, the Bragg reflection structure of the bulk acoustic wave resonator includes a non-conductive reflection structure and a conductive reflection structure. By arranging the non-conductive reflection structure between the substrate and the first electrode layer, the sound wave transmission coefficient can be maintained without damaging the sound wave transmission coefficient, and the sound wave can still be effectively prevented from being transmitted to the substrate through the Bragg reflection structure. Moreover, since the materials of the non-conductive reflection structure are all non-conductive materials, there is no need to perform patterning on them, which can reduce the number of metal etching times and reduce the difficulty of the process preparation of the Bragg reflection structure.

[0020] Furthermore, when the number of periods of the Bragg reflection structure is fixed, the number of layers of the non-conductive reflection structure is increased, and the number of layers of the corresponding conductive reflection structure is reduced. The steps generated by metal etching become smaller, which further reduces the difficulty of process preparation and improves product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0022] Figure 1a and Figure 1b The schematic diagrams of the structures of the solid-state assembled bulk acoustic wave resonators in the prior art are shown respectively;

[0023] Figure 2 Show Figure 1a and Figure 1b A schematic diagram of the transmission coefficient of the Bragg reflection layer in the solid-state assembly type bulk acoustic wave resonator is shown;

[0024] Figure 3 A schematic structural diagram of a solid-state assembly type bulk acoustic wave resonator provided by a first embodiment of the present invention is shown;

[0025] Figure 4 A schematic structural diagram of a solid-state assembly type bulk acoustic wave resonator provided in a second embodiment of the present invention is shown;

[0026] Figure 5 A schematic structural diagram of a solid-state assembly type bulk acoustic wave resonator provided in a third embodiment of the present invention is shown;

[0027] Figure 6 A schematic diagram showing the transmission coefficient of the Bragg reflection layer in the solid-state assembly type bulk acoustic wave resonator provided by the third embodiment of the present invention;

[0028] Figure 7a-7l A schematic diagram showing different stages of a method for preparing a solid-state assembled bulk acoustic wave resonator provided by an embodiment of the present invention;

[0029] Figure 8a-8lA schematic diagram showing different stages of a method for preparing a solid-state assembled bulk acoustic wave resonator provided by another embodiment of the present invention. DETAILED DESCRIPTION

[0030] Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In each of the accompanying drawings, the same elements are represented by the same or similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not drawn to scale.

[0031] The specific implementation of the present invention is further described in detail below in conjunction with the drawings and examples.

[0032] The solid-state matching bulk acoustic wave resonator 100 in the prior art includes a substrate 110, a Bragg reflection structure 120, a first electrode layer 130, a piezoelectric layer 140, and a second electrode layer 150. The Bragg reflection structure is composed of high acoustic impedance layers 121 and low acoustic impedance layers 122 stacked alternately (see Figure 1a and Figure 1b ). The performance of the bulk acoustic wave resonator, especially the resonator quality factor (Quality Factor, Q), is closely related to the structural design of its Bragg acoustic wave reflection layer. On the one hand, it is necessary to select suitable materials for the high acoustic impedance layer 121 and the low acoustic impedance layer 122, and on the other hand, it is necessary to determine the appropriate number of layers. The material of the high acoustic impedance layer 121 usually has a larger density and elastic modulus, such as tungsten, molybdenum, etc.; the material of the low acoustic impedance layer 122 usually has a smaller density and elastic modulus, such as silicon dioxide, silicon nitride, etc. In addition, the number of layers of the Bragg reflection layer is determined by theoretical calculation and simulation. Generally speaking, increasing the number of layers can improve the reflection efficiency, but it will increase the manufacturing difficulty and cost.

[0033] Figure 1b The Bragg reflection structure is Figure 1a The Bragg reflection structure adds a layer of high acoustic impedance. Figure 2 , the dotted line indicates Figure 1a The sound wave transmission coefficient of the Bragg sound wave reflection structure is shown in the solid line. Figure 1b The acoustic wave transmission coefficient of the Bragg acoustic wave reflection structure, Figure 1a and Figure 1b The maximum reflection frequency of the Bragg reflection structure 120 is about 2.3 GHz. Figure 1b The Bragg reflection structure has a better ability to limit sound waves than Figure 1a The Bragg reflection structure has been improved.

[0034] Figure 1bThe Bragg reflection structure in the resonator contains three layers of metal, which requires three photolithography and etching processes. Each photolithography process needs to be aligned with the pattern formed by the previous photolithography. In addition, metal etching will form steps at the edge of the resonator, and the height of the steps formed by the accumulation of multiple layers of metal becomes larger. Both of these factors increase the complexity of the process, the device performance is more affected by the process accuracy, and the product production yield is reduced.

[0035] In order to solve the above problems, the present application provides a solid-state assembled bulk acoustic wave resonator, whose Bragg reflection structure includes a non-conductive reflection structure and a conductive reflection structure. By arranging the non-conductive reflection structure between the substrate and the first electrode layer, the sound wave transmission coefficient can be not damaged, and the sound wave can still be effectively prevented from being transmitted to the substrate through the Bragg reflection structure. Moreover, since the materials of the non-conductive reflection structure are all non-conductive materials, there is no need to perform patterning on them, which can reduce the number of metal etching times and reduce the difficulty of the process preparation of the Bragg reflection structure.

[0036] Figure 3 FIG. 2 is a schematic diagram showing the structure of a solid-state assembly type bulk acoustic wave resonator provided by the first embodiment of the present invention. Figure 3 As shown, the solid-state assembly type BAW resonator 200 includes a substrate 210 , a Bragg reflection structure 220 , a first electrode layer 230 , a piezoelectric layer 240 and a second electrode layer 250 .

[0037] The Bragg reflection structure 220 includes a non-conductive reflection structure 221 and a conductive reflection structure 222 .

[0038] The non-conductive reflective structure 221 and the conductive reflective structure 222 both include high acoustic impedance layers and low acoustic impedance layers that are alternately stacked. The materials of the high acoustic impedance layer and the low acoustic impedance layer of the non-conductive reflective structure 221 are both non-conductive materials, and the material of at least one of the high acoustic impedance layer and the low acoustic impedance layer of the conductive reflective structure 222 is a conductive material. The conductive material is, for example, a metal material and / or an alloy material, but is not limited thereto.

[0039] In some embodiments, a high acoustic impedance layer and a low acoustic impedance layer are sequentially deposited on the substrate 210 to form the Bragg reflection structure 220 , or a low acoustic impedance layer and a high acoustic impedance layer are sequentially deposited on the substrate to form the Bragg reflection structure 220 .

[0040] The non-conductive reflective structure 221 is located on the substrate 210 and completely covers the substrate 210 . The conductive reflective structure 222 is located between the non-conductive reflective structure 221 and the first electrode layer 230 and partially covers the non-conductive reflective structure 221 .

[0041] The non-conductive reflective structure 221 includes alternately stacked first high acoustic impedance layers 2211 and first low acoustic impedance layers 2212, wherein the materials of the first high acoustic impedance layers 2211 and the first low acoustic impedance layers 2212 are both non-conductive materials. The non-conductive reflective structure 221 is a first periodic structure, and its first period number is at least 1.

[0042] Optionally, the material of the first high acoustic impedance layer 2211 is at least one of aluminum nitride, tantalum pentoxide, hafnium oxide, aluminum oxide, silicon carbide, boron nitride, zirconium oxide, titanium oxide, and tungsten oxide, but is not limited thereto.

[0043] Optionally, the material of the first low acoustic impedance layer 2212 is at least one of silicon dioxide, silicon nitride, magnesium oxide, a nanoporous mixture (such as nanoporous methyl silsesquioxane), aerogel, xerogel or a polymer material (such as phenylpropylcyclobutene), but is not limited thereto.

[0044] The conductive reflective structure 222 comprises alternately stacked second high acoustic impedance layers 2221 and second low acoustic impedance layers 2222, wherein the second high acoustic impedance layers 2221 and the second low acoustic impedance layers 2222 are both made of non-conductive materials. The conductive reflective structure 222 is a second periodic structure, and its second period number is at least 1.

[0045] Optionally, the material of the second high acoustic impedance layer 2221 is at least one of tungsten, titanium tungsten, molybdenum, platinum, ruthenium, iridium, hafnium, tantalum, nickel, chromium, cobalt, zirconium carbide, cobalt oxide, aluminum nitride, tantalum pentoxide, hafnium oxide, aluminum oxide, silicon carbide, boron nitride, zirconium oxide, titanium oxide, and tungsten oxide, but is not limited thereto.

[0046] Optionally, the material of the second low acoustic impedance layer 2222 is at least one of aluminum, magnesium, silicon dioxide, silicon nitride, magnesium oxide, a nanoporous mixture (such as nanoporous methyl silsesquioxane), aerogel, dry gel or polymer material (such as phenylpropylcyclobutene), but is not limited thereto.

[0047] In some implementations, the second high acoustic impedance layer 2221 and the second low acoustic impedance layer 2222 are both made of conductive materials, and the second high acoustic impedance layer 2221 and the second low acoustic impedance layer 2222 are both patterned to partially cover the non-conductive reflective structure 221 .

[0048] In some implementations, the second high acoustic impedance layer 2221 is a conductive material, the second low acoustic impedance layer 2222 is a non-conductive material, the second low acoustic impedance layer 2222 completely covers the non-conductive reflective structure 221 , and the second high acoustic impedance layer 2221 is patterned to partially cover the non-conductive reflective structure 221 .

[0049] In some implementations, the second high acoustic impedance layer 2221 is a non-conductive material, the second low acoustic impedance layer 2222 is a conductive material, the second high acoustic impedance layer 2221 completely covers the non-conductive reflective structure 221 , and the second low acoustic impedance layer 2222 is patterned to partially cover the non-conductive reflective structure 221 .

[0050] Since both the non-conductive reflection structure 221 and the conductive reflection structure 222 are periodic structures, the Bragg reflection structure 220 is also a periodic structure, and the period of the Bragg reflection structure 220 is at least 3.

[0051] The solid-state assembled bulk acoustic wave resonator provided by the present application has a Bragg reflection structure including a non-conductive reflection structure and a conductive reflection structure. By arranging the non-conductive reflection structure between the substrate and the first electrode layer, the sound wave transmission coefficient can be maintained without damaging the sound wave transmission coefficient through the Bragg reflection structure. Moreover, since the materials of the non-conductive reflection structure are all non-conductive materials, there is no need to perform patterning on them, which can reduce the number of metal etching times and reduce the difficulty of the process preparation of the Bragg reflection structure.

[0052] Furthermore, when the number of periods of the Bragg reflection structure is fixed, the number of layers of the non-conductive reflection structure is increased, and the number of layers of the corresponding conductive reflection structure is reduced. The steps generated by metal etching become smaller, which further reduces the difficulty of process preparation and improves product yield.

[0053] Figure 4 FIG. 2 is a schematic diagram showing the structure of a solid-state assembly type bulk acoustic wave resonator provided by a second embodiment of the present invention. Figure 4 As shown, the BAW resonator 300 includes a substrate 310 , a Bragg reflection structure 320 , a first electrode layer 330 , a piezoelectric layer 340 and a second electrode layer 350 .

[0054] The Bragg reflection structure 320 includes a non-conductive reflection structure 321 and a conductive reflection structure 322 .

[0055] The non-conductive reflective structure 321 and the conductive reflective structure 322 both include high acoustic impedance layers and low acoustic impedance layers that are alternately stacked. The materials of the high acoustic impedance layer and the low acoustic impedance layer of the non-conductive reflective structure 321 are both non-conductive materials, and the material of at least one of the high acoustic impedance layer and the low acoustic impedance layer of the conductive reflective structure 322 is a conductive material. The conductive material is, for example, a metal material and / or an alloy material, but is not limited thereto.

[0056] In some embodiments, a high acoustic impedance layer and a low acoustic impedance layer are sequentially deposited on the substrate 310 to form the Bragg reflection structure 320 , or a low acoustic impedance layer and a high acoustic impedance layer are sequentially deposited on the substrate to form the Bragg reflection structure 320 .

[0057] The non-conductive reflective structure 321 is located on the substrate 310 and completely covers the substrate 310 . The conductive reflective structure 322 is located between the non-conductive reflective structure 321 and the first electrode layer 330 and partially covers the non-conductive reflective structure 321 .

[0058] The non-conductive reflective structure 321 includes alternately stacked first high acoustic impedance layers 3211 and first low acoustic impedance layers 3212, wherein the materials of the first high acoustic impedance layers 3211 and the first low acoustic impedance layers 3212 are both non-conductive materials. The non-conductive reflective structure 321 is a first periodic structure, and its first period number is at least 1.

[0059] Optionally, the material of the first high acoustic impedance layer 3211 is at least one of aluminum nitride, tantalum pentoxide, hafnium oxide, aluminum oxide, silicon carbide, boron nitride, zirconium oxide, titanium oxide, and tungsten oxide, but is not limited thereto.

[0060] Optionally, the material of the first low acoustic impedance layer 3212 is at least one of silicon dioxide, silicon nitride, magnesium oxide, a nanoporous mixture (such as nanoporous methyl silsesquioxane), aerogel, xerogel or a polymer material (such as phenylpropylcyclobutene), but is not limited thereto.

[0061] The conductive reflective structure 322 includes alternately stacked second high acoustic impedance layers 3221 and second low acoustic impedance layers 3222, wherein the second high acoustic impedance layers 3221 and the second low acoustic impedance layers 3222 are both made of non-conductive materials. The conductive reflective structure 322 is a second periodic structure, and its second period number is at least 1.

[0062] Optionally, the material of the second high acoustic impedance layer 3221 is at least one of tungsten, titanium tungsten, molybdenum, platinum, ruthenium, iridium, hafnium, tantalum, nickel, chromium, cobalt, zirconium carbide, cobalt oxide, aluminum nitride, tantalum pentoxide, hafnium oxide, aluminum oxide, silicon carbide, boron nitride, zirconium oxide, titanium oxide, and tungsten oxide, but is not limited thereto.

[0063] Optionally, the material of the second low acoustic impedance layer 3222 is at least one of aluminum, magnesium, silicon dioxide, silicon nitride, magnesium oxide, a nanoporous mixture (such as nanoporous methyl silsesquioxane), aerogel, dry gel or polymer material (such as phenylpropylcyclobutene), but is not limited thereto.

[0064] In some implementations, the second high acoustic impedance layer 3221 and the second low acoustic impedance layer 3222 are both made of conductive materials, and the second high acoustic impedance layer 3221 and the second low acoustic impedance layer 3222 are both patterned to partially cover the non-conductive reflective structure 321 .

[0065] In some implementations, the second high acoustic impedance layer 3221 is a conductive material, the second low acoustic impedance layer 3222 is a non-conductive material, the second low acoustic impedance layer 3222 completely covers the non-conductive reflective structure 321 , and the second high acoustic impedance layer 3221 is patterned to partially cover the non-conductive reflective structure 321 .

[0066] In some implementations, the second high acoustic impedance layer 3221 is a non-conductive material, the second low acoustic impedance layer 3222 is a conductive material, the second high acoustic impedance layer 3221 completely covers the non-conductive reflective structure 321 , and the second low acoustic impedance layer 3222 is patterned to partially cover the non-conductive reflective structure 321 .

[0067] Since both the non-conductive reflection structure 321 and the conductive reflection structure 322 are periodic structures, the Bragg reflection structure 320 is also a periodic structure, and the number of periods of the Bragg reflection structure 320 is at least three.

[0068] Compared with the first embodiment, the period number of the non-conductive reflective structure in this embodiment is 1, and the period number of the conductive reflective structure is 2.

[0069] Figure 5 The schematic diagram of the structure of the solid-state assembly type bulk acoustic wave resonator provided by the third embodiment of the present invention is shown. Compared with the first embodiment, the period number of the non-conductive reflective structure in the present application is 2, and the period number of the conductive reflective structure is 2. The rest is the same as the first embodiment and will not be repeated here.

[0070] Figure 6 Graph 2 shows the transmission coefficient of the Bragg reflection structure of the third embodiment of the present invention. Figure 1b Compared with the solid-state assembled bulk acoustic wave resonator structure shown, the acoustic wave transmission coefficient of the hybrid Bragg acoustic wave reflection structure does not decrease in the same frequency range, but since a non-conductive reflection structure is added between the substrate and the conductive reflection structure, the process is simplified and the manufacturing difficulty is reduced.

[0071] Figure 7a-7l The schematic diagram shows different stages of the method for preparing a solid-state assembled BAW resonator provided by the present invention. The method for preparing a solid-state assembled BAW resonator comprises the following steps.

[0072] In step S110, a Bragg reflection structure 420 is formed on a substrate 410. In some embodiments, step S110 includes step S111 and step S112.

[0073] In step S111 , high acoustic impedance layers and low acoustic impedance layers are alternately deposited on the substrate 410 to form a non-conductive reflective structure 421 .

[0074] Specifically, a first high acoustic impedance layer 4211 and a first low acoustic impedance layer 4212 are alternately deposited on the substrate 410 to form a non-conductive reflective structure 421 (see Figure 7a-Figure 7b ). In this embodiment, Figure 6 The solid-state assembly type BAW resonator is used as an example for explanation. The number of periods of the non-conductive reflective structure 421 can be set according to actual conditions and is not limited to that shown in the above embodiment.

[0075] In step S112 , high acoustic impedance layers and low acoustic impedance layers are alternately deposited on the non-conductive reflective structure 421 and patterned to form a conductive reflective structure 422 .

[0076] Specifically, the second high acoustic impedance layer 4221 and the second low acoustic impedance layer 4222 are alternately deposited on the non-conductive reflective structure 421 to form a conductive reflective structure 422 (see Figure 7c-7f ). The number of periods of the conductive reflective structure 422 can be set according to actual conditions and is not limited to that shown in the above embodiments.

[0077] In this embodiment, the second high acoustic impedance layer 4221 and the second low acoustic impedance layer 4222 are both patterned to partially cover the non-conductive reflective structure 421 as an example for description, but the invention is not limited thereto.

[0078] In some implementations, the second high acoustic impedance layer 4221 and the second low acoustic impedance layer 4222 are both made of conductive materials, and the second high acoustic impedance layer 4221 and the second low acoustic impedance layer 4222 are both patterned to partially cover the non-conductive reflective structure 421 .

[0079] In some implementations, the second high acoustic impedance layer 4221 is a conductive material, the second low acoustic impedance layer 4222 is a non-conductive material, the second low acoustic impedance layer 4222 completely covers the non-conductive reflective structure 421 , and the second high acoustic impedance layer 4221 is patterned to partially cover the non-conductive reflective structure 421 .

[0080] In some implementations, the second high acoustic impedance layer 4221 is a non-conductive material, the second low acoustic impedance layer 4222 is a conductive material, the second high acoustic impedance layer 4221 completely covers the non-conductive reflective structure 421 , and the second low acoustic impedance layer 4222 is patterned to partially cover the non-conductive reflective structure 421 .

[0081] In step S120 , a first electrode layer 430 , a piezoelectric layer 440 , and a second electrode layer 450 are sequentially formed on the Bragg reflection structure 420 .

[0082] Specifically, a first electrode is provided on the Bragg reflection structure 420 and a first electrode layer 430 is formed by patterning (see Figure 7g-7h); providing a piezoelectric layer on the first electrode layer 430 and patterning the piezoelectric layer 440 (see Figure 7i-7j ); providing a second electrode on the piezoelectric layer 440 and patterning to form a second electrode layer 450 (see Figure 7k-7l ).

[0083] The method for preparing a bulk acoustic wave resonator provided in the present application sequentially forms a non-conductive reflection structure and a conductive reflection structure on a substrate as a Bragg reflection structure, which can prevent the sound wave transmission coefficient from being damaged and can still effectively prevent the sound wave from being transmitted to the substrate through the Bragg reflection structure. Moreover, since the material of the non-conductive reflection structure is all non-conductive material, there is no need to perform patterning on it, which can reduce the number of metal etching times and reduce the difficulty of the process preparation of the Bragg reflection structure.

[0084] Furthermore, when the number of periods of the Bragg reflection structure is fixed, the number of layers of the non-conductive reflection structure is increased, and the number of layers of the corresponding conductive reflection structure is reduced. The steps generated by metal etching become smaller, which further reduces the difficulty of process preparation and improves product yield.

[0085] Figure 8a-8l A schematic diagram showing different stages of a method for preparing a solid-state assembly type BAW resonator provided by another embodiment of the present invention is shown. The method for preparing a solid-state assembly type BAW resonator comprises the following steps.

[0086] In step S210, a Bragg reflection structure 520 is formed on a substrate 510. In some embodiments, step S210 includes step S211 and step S212.

[0087] In step S211 , high acoustic impedance layers and low acoustic impedance layers are alternately deposited on the substrate 510 to form a non-conductive reflective structure 521 .

[0088] Specifically, a first high acoustic impedance layer 5211 and a first low acoustic impedance layer 5212 are alternately deposited on the substrate 510 to form a non-conductive reflective structure 521 (see Figure 8a-8b ). In this embodiment, Figure 6 The solid-state assembly type BAW resonator is used as an example for explanation. The number of periods of the non-conductive reflective structure 521 can be set according to actual conditions and is not limited to that shown in the above embodiment.

[0089] In step S212 , high acoustic impedance layers and low acoustic impedance layers are alternately deposited on the non-conductive reflective structure 521 and patterned to form a conductive reflective structure 522 .

[0090] Specifically, a second high acoustic impedance layer 5221 and a second low acoustic impedance layer 5222 are alternately deposited on the non-conductive reflective structure 521 to form a conductive reflective structure 522 (see Figure 8c-8f). The number of periods of the conductive reflective structure 522 can be set according to actual conditions and is not limited to that shown in the above embodiment. In this embodiment, one layer of the conductive reflective structure 522 is a conductive material, and the other layer is a non-conductive material. Only the conductive material is patterned to partially cover the non-conductive reflective structure 521 as an example for illustration, but it is not limited to this.

[0091] In some implementations, the second high acoustic impedance layer 5221 is a conductive material, the second low acoustic impedance layer 5222 is a non-conductive material, the second low acoustic impedance layer 5222 completely covers the non-conductive reflective structure 521 , and the second high acoustic impedance layer 5221 is patterned to partially cover the non-conductive reflective structure 521 .

[0092] In some implementations, the second high acoustic impedance layer 5221 is a non-conductive material, the second low acoustic impedance layer 5222 is a conductive material, the second high acoustic impedance layer 5221 completely covers the non-conductive reflective structure 521 , and the second low acoustic impedance layer 5222 is patterned to partially cover the non-conductive reflective structure 521 .

[0093] In step S220 , a first electrode layer 530 , a piezoelectric layer 540 , and a second electrode layer 550 are sequentially formed on the Bragg reflection structure 520 .

[0094] Specifically, a first electrode is provided on the Bragg reflection structure 520 and a first electrode layer 530 is formed by patterning (see Figure 8g-Figure 8h ); providing a piezoelectric layer on the first electrode layer 530 and patterning the piezoelectric layer 540 (see Figure 8i-8j ); providing a second electrode on the piezoelectric layer 540 and patterning to form a second electrode layer 550 (see Figure 8k-8l ).

[0095] The method for preparing a bulk acoustic wave resonator provided in the present application sequentially forms a non-conductive reflection structure and a conductive reflection structure on a substrate as a Bragg reflection structure, which can prevent the sound wave transmission coefficient from being damaged and can still effectively prevent the sound wave from being transmitted to the substrate through the Bragg reflection structure. Moreover, since the material of the non-conductive reflection structure is all non-conductive material, there is no need to perform patterning on it, which can reduce the number of metal etching times and reduce the difficulty of the process preparation of the Bragg reflection structure.

[0096] Furthermore, when the number of periods of the Bragg reflection structure is fixed, the number of layers of the non-conductive reflection structure is increased, and the number of layers of the corresponding conductive reflection structure is reduced. The steps generated by metal etching become smaller, which further reduces the difficulty of process preparation and improves product yield.

[0097] Furthermore, one of the high acoustic impedance layer and the low acoustic impedance layer in the conductive reflective structure is made of conductive material, and the other is made of non-conductive material. When forming the conductive reflective structure, only the metal material layer is patterned, which further reduces the number of metal etching times and reduces the difficulty of the process preparation of the Bragg reflective structure.

[0098] According to the embodiments of the present invention as described above, these embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and the modified use based on the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A solid-state assembled bulk acoustic wave resonator, characterized in that: It includes a substrate, a Bragg reflection structure, a first electrode layer, a piezoelectric layer and a second electrode layer which are sequentially stacked on the substrate; The Bragg reflection structure includes a non-conductive reflection structure and a conductive reflection structure, and both the non-conductive reflection structure and the conductive reflection structure include alternately stacked high acoustic impedance layers and low acoustic impedance layers. The materials of the high acoustic impedance layer and the low acoustic impedance layer of the non-conductive reflection structure are both non-conductive materials, and the material of at least one of the high acoustic impedance layer and the low acoustic impedance layer of the conductive reflection structure is a conductive material, and the conductive material is generally a metal or an alloy.

2. The solid-state assembly type bulk acoustic wave resonator according to claim 1, characterized in that: The non-conductive reflective structure is located on the substrate and completely covers the substrate, the conductive reflective structure is located between the non-conductive reflective structure and the first electrode layer, and the conductive reflective structure partially covers the non-conductive reflective structure.

3. The solid-state assembly type bulk acoustic wave resonator according to claim 1, characterized in that: The non-conductive reflective structure is a first periodic structure, each first period includes a first high acoustic impedance layer and a first low acoustic impedance layer, and the number of first periods is at least 1; the conductive reflective structure is a second periodic structure, each second period includes a second high acoustic impedance layer and a second low acoustic impedance layer, and the number of second periods is at least 1.

4. The solid-state assembly type bulk acoustic wave resonator according to claim 1, characterized in that: The period number of the Bragg reflection structure is at least 3.

5. The solid-state assembly type bulk acoustic wave resonator according to claim 3, characterized in that: The material of the first high acoustic impedance layer is at least one of aluminum nitride, tantalum pentoxide, hafnium oxide, aluminum oxide, silicon carbide, boron nitride, zirconium oxide, titanium oxide, and tungsten oxide; the material of the first low acoustic impedance layer is at least one of silicon dioxide, silicon nitride, magnesium oxide, nanoporous mixture, aerogel, dry gel or polymer material.

6. The solid-state assembly type bulk acoustic wave resonator according to claim 3, characterized in that: The material of the second high acoustic impedance layer is at least one of tungsten, titanium tungsten, molybdenum, platinum, ruthenium, iridium, hafnium, tantalum, nickel, chromium, cobalt, zirconium carbide, cobalt oxide, aluminum nitride, tantalum pentoxide, hafnium oxide, aluminum oxide, silicon carbide, boron nitride, zirconium oxide, titanium oxide, and tungsten oxide; the material of the second low acoustic impedance layer is at least one of aluminum, magnesium, silicon dioxide, silicon nitride, magnesium oxide, nanoporous mixture, aerogel, dry gel or polymer material.

7. The solid-state assembly type bulk acoustic wave resonator according to claim 1, characterized in that: When the second high acoustic impedance layer and the second low acoustic impedance layer are both made of conductive materials, the second high acoustic impedance layer and the second low acoustic impedance layer partially cover the non-conductive reflective structure; When the material of the second high acoustic impedance layer is a conductive material and the material of the second low acoustic impedance layer is a non-conductive material, the second low acoustic impedance layer completely covers the non-conductive reflective structure, and the second high acoustic impedance layer partially covers the non-conductive reflective structure; When the material of the second high acoustic impedance layer is non-conductive material and the material of the second low acoustic impedance layer is conductive material, the second high acoustic impedance layer completely covers the non-conductive reflective structure and the second low acoustic impedance layer partially covers the non-conductive reflective structure.

8. A method for preparing a solid-state assembled bulk acoustic wave resonator according to any one of claims 1 to 7, characterized in that: include: forming a Bragg reflection structure on a substrate; forming a first electrode layer, a piezoelectric layer, and a second electrode layer in sequence on the Bragg reflection structure; Wherein, forming a Bragg reflection structure on the substrate comprises: A high acoustic impedance layer and a low acoustic impedance layer are alternately deposited on a substrate to form a non-conductive reflective structure; Alternately depositing high acoustic impedance layers and low acoustic impedance layers on the non-conductive reflective structure and patterning them to form a conductive reflective structure; The materials of the high acoustic impedance layer and the low acoustic impedance layer of the non-conductive reflective structure are both non-conductive materials, and the material of at least one of the high acoustic impedance layer and the low acoustic impedance layer of the conductive reflective structure is conductive material.

9. The method for preparing a solid-state assembled bulk acoustic wave resonator according to claim 8, characterized in that: The high acoustic impedance layer and the low acoustic impedance layer of the conductive reflective structure are both patterned to form a conductive reflective structure, wherein the conductive reflective structure partially covers the non-conductive reflective structure.

10. The method for preparing a solid-state assembled bulk acoustic wave resonator according to claim 8, characterized in that: One layer of the conductive reflective structure is patterned, and the other layer is not patterned to form a conductive reflective structure, wherein one layer partially covers the non-conductive reflective structure, and the other layer completely covers the non-conductive reflective structure; The material of one layer is a conductive material, and the material of the other layer is a non-conductive material.

Images