CN114006594A - A kind of bulk acoustic wave resonator and preparation method thereof - Google Patents

Abstract

Disclosed herein is a bulk acoustic wave resonator and a method for preparing the same. The bulk acoustic wave resonator includes: a top electrode, a piezoelectric material film, a bottom electrode and a substrate; wherein, the area delimited by the outer periphery of the top electrode is provided with more than one first pass through The piezoelectric material film is provided with one or more second through holes; the area delineated by the outer circumference of the bottom electrode is provided with more than one third through hole; wherein the first through hole, the second through hole and the third through hole are used for Corrosive fluid by etching cavities on the substrate. In the embodiment of the present invention, without applying the sacrificial layer process, the photolithography process on the backside of the substrate and the Bragg reflection layer, the first through hole, the second through hole and the third through hole are provided, and the etching is performed on the substrate by etching The corrosive fluid that corrodes the cavity simplifies the preparation process of the bulk acoustic wave resonator.

Description

A kind of bulk acoustic wave resonator and preparation method thereof

technical field

This article relates to but not limited to radio frequency communication technology, especially to a bulk acoustic wave resonator and its preparation method.

Background technique

Micro-Electro-Mechanical System (MEMS) resonators are widely used in the field of radio frequency communications, and play an extremely important role in the manufacture of micro-filters, duplexers, and multiplexers. The surface acoustic wave resonator technology in the related art is mature, and the resonant frequency can be adjusted by changing the lithography pattern. However, due to the constraints of the lithography process conditions and the limitation of the speed of sound in the piezoelectric material, it is difficult to be above 2.5 gigahertz (GHz). At the same time, it has high electromechanical coupling coefficient and quality factor, and its manufacturing process is difficult to be compatible with the processing technology of complementary metal oxide semiconductor, which does not conform to the development trend of miniaturization and integration of electronic products. The bulk acoustic wave resonator in the related art can be applied to the ultra-high frequency field, but the process is relatively complicated, and the thickness of the piezoelectric film is small when the resonance frequency is high, and the quality is difficult to guarantee. Lamb wave resonators can have high electromechanical coupling coefficients at ultra-high frequencies, but they have stricter requirements on lithography equipment and process conditions, and the intensity and number of spurious modes are also greater than those of bulk acoustic wave resonators.

Aluminum nitride is a piezoelectric material that has been widely used in MEMS resonators in recent years. It has the advantages of stable chemical properties, good process repeatability, and high thermal stability of material parameters. The main problems of making filters with center frequency above 3GHz based on aluminum nitride resonators are complex process, narrow process window, low electromechanical coupling coefficient, and poor quality of aluminum nitride, which are difficult to meet the requirements of mass production. Therefore, there is a need for a resonator with a new structure that can meet the electrical requirements of UHF filters.

SUMMARY OF THE INVENTION

The following is an overview of the topics detailed in this article. This summary is not intended to limit the scope of protection of the claims.

The embodiments of the present invention provide a bulk acoustic wave resonator and a preparation method thereof, which can reduce the requirements of the bulk acoustic wave resonator on the lithography process and simplify the preparation process of the bulk acoustic wave resonator.

An embodiment of the present invention provides a bulk acoustic wave resonator, comprising: a top electrode 1, a piezoelectric material film 2, a bottom electrode 3 and a substrate 4; wherein,

The top electrode (1) is provided with one or more first through holes (1-1) in the area delineated by the outer peripheral contour, and the piezoelectric material film (2) is provided with one or more second through holes (2-1); the bottom electrode (3) ) is provided with more than one third through hole (3-1) in the area delineated by the outer peripheral contour of the );

Wherein, the first through hole (1-1), the second through hole (2-1) and the third through hole (3-1) are used to etch holes on the substrate (4) The corrosive fluid of the cavity; the first projection area of the second through hole (2-1) on the area delineated by the outer peripheral contour of the top electrode (1) and the first projection area of the first through hole (1-1) The overlapping area is the first hollow area; the second projection area of the second through hole (2-1) on the area delineated by the outer peripheral contour of the bottom electrode (3) and the third through hole (3-1) ) overlapping area is the second hollow area.

An embodiment of the present invention also provides a method for preparing a bulk acoustic wave resonator, comprising:

depositing a bottom electrode material and a bottom electrode lead-out electrode material on the upper surface of the substrate, and performing a patterning process to obtain a bottom electrode lead-out electrode and a bottom electrode including a third through hole;

A piezoelectric material film is prepared on the surface of the bottom electrode material;

etching the piezoelectric material film to obtain a second through hole;

A top electrode material and a top electrode lead-out electrode material are deposited on the upper surface of the piezoelectric material film, and patterned to obtain a top electrode lead-out electrode and a top electrode including a first through hole;

The corrosive fluid flows to the substrate etching cavity through the first through hole, the second through hole and the third through hole, and releases the bulk acoustic wave resonator;

Wherein, the first projection area of the second through hole on the area delineated by the outer circumference of the top electrode and the overlapping area of the first through hole is the first hollow area; the second through hole is in the bottom electrode The overlapping area of the second projection area and the third through hole on the area delineated by the outer peripheral contour is the second hollow area.

The technical solution of the present application includes: a top electrode 1, a piezoelectric material film 2, a bottom electrode 3 and a substrate 4; wherein, the area delineated by the outer circumference of the top electrode 1 is provided with more than one first through hole 1-1, and the piezoelectric material The film 2 is provided with one or more second through holes 2-1; the area delineated by the outer periphery of the bottom electrode 3 is provided with more than one third through hole 3-1; The second through hole 2-1 and the third through hole 3-1 are used to pass the corrosive fluid that etches the cavity on the substrate 4; the second through hole 2-1 is delineated on the outer circumference of the top electrode 1 The overlapping area of the first projection area and the first through hole 1-1 on the area is the first hollow area; The overlapping area of the projected area and the third through hole 3-1 is the second hollow area. In the embodiment of the present invention, the first through hole 1-1, the second through hole 2-1 and the third through hole 3 are provided through the first through hole 1-1, the second through hole 2-1 and the third through hole 3 without applying the sacrificial layer process, the substrate backside lithography process and the Bragg reflection layer. -1, By etching the corrosive fluid of the cavity on the substrate, the fabrication process of the bulk acoustic wave resonator is simplified.

Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the description, claims and drawings.

Description of drawings

The accompanying drawings are used to provide a further understanding of the technical solutions of the present invention, and constitute a part of the specification. They are used to explain the technical solutions of the present invention together with the embodiments of the present application, and do not limit the technical solutions of the present invention.

1 is a perspective view of a bulk acoustic wave resonator according to an embodiment of the present invention;

2 is a cross-sectional view of a bulk acoustic wave resonator according to an embodiment of the present invention;

3 is a schematic diagram of an admittance curve of a bulk acoustic wave resonator according to an embodiment of the present invention;

4 is a schematic diagram of an admittance curve of a bulk acoustic wave resonator according to another embodiment of the present invention;

5 is a schematic diagram of an admittance curve of a bulk acoustic wave resonator according to another embodiment of the present invention;

6 is a two-dimensional partial schematic diagram of a bulk acoustic wave resonator according to an embodiment of the present invention;

7 is a schematic diagram of an isolation layer according to an embodiment of the present invention;

8 is a schematic diagram of a gap according to an embodiment of the present invention;

9 is a schematic diagram of an isolation trench according to an embodiment of the present invention;

FIG. 10 is a schematic diagram of a lead-out electrode according to an embodiment of the present invention;

11 is a flowchart of a method for preparing a bulk acoustic wave resonator according to an embodiment of the present invention;

12 is a schematic diagram of the composition of a bulk acoustic wave resonator prepared according to an embodiment of the present invention;

13 is a schematic diagram of the composition of a bulk acoustic wave resonator prepared according to another embodiment of the present invention;

FIG. 14 is a schematic diagram of the composition of a bulk acoustic wave resonator prepared according to still another embodiment of the present invention;

15 is a schematic diagram of the composition of a bulk acoustic wave resonator prepared according to another embodiment of the present invention;

FIG. 16 is a schematic diagram of the composition of a bulk acoustic wave resonator prepared according to another embodiment of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, the embodiments in the present application and the features in the embodiments may be arbitrarily combined with each other if there is no conflict.

The steps shown in the flowcharts of the figures may be performed in a computer system, such as a set of computer-executable instructions. Also, although a logical order is shown in the flowcharts, in some cases the steps shown or described may be performed in an order different from that herein.

1 is a perspective view of a bulk acoustic wave resonator according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a bulk acoustic wave resonator according to an embodiment of the present invention. As shown in FIGS. 1 and 2 , the bulk acoustic wave resonator according to the embodiment of the present invention includes: a top Electrode 1, piezoelectric material film 2, bottom electrode 3 and substrate 4; wherein,

The area delineated by the outer periphery of the top electrode 1 is provided with more than one first through hole 1-1, the piezoelectric material film 2 is provided with more than one second through hole 2-1; the area delimited by the outer periphery of the bottom electrode 3 is provided with one or more first through holes 1-1. The above third through hole 3-1;

Among them, the first through hole 1-1, the second through hole 2-1 and the third through hole 3-1 are used to pass the corrosive fluid that etches the cavity on the substrate 4; the second through hole 2-1 is in The overlapping area of the first projection area and the first through hole 1-1 on the area delineated by the outer circumference of the top electrode 1 is the first hollow area; the second through hole 2-1 is on the area delineated by the outer circumference of the bottom electrode 3 The overlapping area of the second projection area and the third through hole 3-1 is the second hollow area.

In the embodiment of the present invention, the first through hole 1-1 and the third through hole 3-1 are respectively provided in the regions delineated by the outer peripheral contours of the top electrode 1 and the bottom electrode 3; in an exemplary embodiment, the embodiment of the present invention The top electrode 1 has and only has a first through hole 1-1, and the bottom electrode 3 has and only has a third through hole 3-1.

In the embodiment of the present invention, the first through hole 1-1, the second through hole 2-1 and the third through hole 3 are provided without the need to apply the sacrificial layer process, the substrate backside photolithography process and the Bragg reflection layer. -1, By etching the corrosive fluid of the cavity on the substrate, the fabrication process of the bulk acoustic wave resonator is simplified.

In an exemplary example, the size and position of the first through hole 1-1, the second through hole 2-1 and the third through hole 3-1 according to the embodiment of the present invention can be determined by those skilled in the art according to the corrosion resistance. The volume of the fluid, the location of the cavity and the etch rate of the substrate are analyzed and set.

In an exemplary example, the corrosive fluid in the embodiment of the present invention may include: xenon difluoride. In an exemplary example, the corrosive fluid of the embodiment of the present invention can be determined by those skilled in the art according to the material of the substrate.

In an exemplary example, the material of the substrate in the embodiment of the present invention may be silicon or silicon carbide, and the substrate 4 is etched with a corrosive fluid to obtain a cavity; the embodiment of the present invention utilizes the substrate to weaken the edge of the bulk acoustic wave resonator The piezoelectric material film 2 and the vibration of the top electrode 1 and the bottom electrode 3, thereby realizing the suppression of spurious modes.

In an exemplary embodiment, the piezoelectric material film 2 according to the embodiment of the present invention is composed of one or more of the following piezoelectric materials:

Aluminum nitride, scandium-doped aluminum nitride, lithium niobate, lithium tantalate, and lead zirconate titanate.

In an exemplary example, the projections of the top electrode 1 on the plane where the top of the bottom electrode 3 is located according to the embodiment of the present invention are all located in the area delineated by the outer periphery of the bottom electrode 3 .

In an exemplary example, the ratio of the area of the first through hole 1-1 in the embodiment of the present invention to the area of the area delineated by the outer periphery of the top electrode 1 is a first preset ratio.

In an exemplary example, the ratio of the area of the second through hole 2 - 1 according to the embodiment of the present invention to the area of the area delineated by the outer peripheral contour of the top electrode 1 is a second preset ratio.

In an exemplary example, the ratio of the area of the third through hole 3 - 1 in the embodiment of the present invention to the area of the area delineated by the outer periphery of the top electrode 1 is a third preset ratio.

In an exemplary example, the first preset ratio in the embodiment of the present invention is greater than 0.001 but less than 0.7; the second preset ratio is greater than 0.001 but less than 0.7; the third preset ratio is greater than 0.001 but less than 0.7.

In an exemplary example, the first preset ratio, the second preset ratio, and the third preset ratio in the embodiment of the present invention can be adjusted by those skilled in the art based on the performance of the prepared bulk acoustic wave resonator. In an exemplary example, the first preset ratio, the second preset ratio, and the third preset ratio in the embodiment of the present invention may be greater than 0.01 but less than 0.09.

In an exemplary example, the ratio of the area of the upper surface of the cavity of the substrate 4 according to the embodiment of the present invention to the area of the area delimited by the outer peripheral contour of the top electrode 1 is a fourth preset ratio.

In an exemplary example, the fourth preset ratio in the embodiment of the present invention is greater than 0.8 but less than 4.

In an exemplary example, the ratio of the area of the first hollowed-out region in the embodiment of the present invention to the area of the region delineated by the outer periphery of the top electrode 1 is a fifth preset ratio;

The ratio of the area of the second hollow area to the area of the area delineated by the outer periphery of the top electrode 1 is a sixth preset ratio;

Wherein, the fifth preset ratio is greater than 0.001 but less than 0.7; the sixth preset ratio is greater than 0.001 but less than 0.7.

In an exemplary embodiment, the fifth preset ratio and the sixth preset ratio in the embodiment of the present invention may be adjusted by those skilled in the art based on the performance of the prepared bulk acoustic wave resonator. In an exemplary embodiment, this In the embodiment of the invention, the fifth preset ratio and the sixth preset ratio may be greater than 0.01 but less than 0.09. In an exemplary embodiment, in the embodiment of the present invention, when the materials of the top electrode 1 and the bottom electrode 3 are both aluminum, the piezoelectric material film 2 is aluminum nitride, the substrate 4 is silicon, and the top electrode 1 and the bottom electrode 3 are made of aluminum. The outer peripheral contour of the upper surface is circular, and the radius of the top electrode 1 and the radius of the bottom electrode 3 are both larger than the radius of the upper surface of the cavity of the substrate 4; the values of each parameter are shown in Table 1; FIG. 3 is an embodiment of the present invention A schematic diagram of the admittance curve of the bulk acoustic wave resonator, the admittance curve of the bulk acoustic wave resonator with a radius of 58 micrometers (μm) on the upper surface of the cavity on the substrate 4 in a small frequency range; FIG. 4 is another diagram of the present invention. A schematic diagram of the admittance curve of a bulk acoustic wave resonator in an embodiment, the admittance curve of a bulk acoustic wave resonator with a radius of 58 μm on the upper surface of the cavity on the substrate 4 in a large frequency range; the cavity on the substrate 4 The ratio of the area of the upper surface of the top electrode 1 to the area of the area delineated by the outer peripheral contour of the top electrode 1 is the fourth _preset ratio; In gigahertz (GHz), the parallel resonance frequency f _p is 5.024 GHz, and the calculated value of the electromechanical coupling coefficient is 7.27%. Under this parameter combination, the radius of the upper surface of the cavity on the substrate 4 is smaller than the radius of the top electrode and the bottom electrode, which weakens the vibration of the piezoelectric material film and the electrode at the edge of the bulk acoustic wave resonator and suppresses the bulk acoustic wave resonator. Spurious modes caused by edges. If the radius of the upper surface of the cavity on the substrate 4 is larger than the radius of the top electrode and the bottom electrode, for example, when r ₃ =62 μm, the admittance curve of the BAW resonator in a small frequency range is shown in FIG. 5 , compared with FIG. 3 Compared with Fig. 5, there are many spurious modes in the admittance curve of Fig. 5.

parameter value/micron parameter value/micron parameter value/micron x₁ 5 r₁ 60 h_t 0.07 x₂ 4 r₂ 60 h_p 1 x₃ 5 r₃ 58 h_b 0.07

Table 1

的大小，采用一阶泰勒近似公式表示为：FIG. 6 is a two-dimensional partial schematic diagram of a bulk acoustic wave resonator according to an embodiment of the present invention. As shown in FIG. 6 , the two-dimensional partial structure rotates 360° along the rotation axis 9 to form a three-dimensional bulk acoustic wave resonator; suppose: the top electrode 1 and the bottom electrode 3 is circular; the number of first through holes 1-1 is 1 and is circular, the number of second through holes 2-1 is 1 and is circular; the number of third through holes 3-1 is 1 and is Circular; the center of the first through hole 1-1 is the geometric center of the top electrode 1, the center of the second through hole 2-1 is the geometric center of the piezoelectric material film 2, and the third through hole 3-1 is the bottom electrode 3 The geometric center of , the meanings of the parameters in the figure are: x ₁ is the radius of the first through hole 1-1, x ₂ is the radius of the second through hole 2-1, x ₃ is the radius of the third through hole 3-1 Radius, r ₁ is the radius of the top electrode 1, r ₂ is the radius of the bottom electrode 3, r ₃ is the radius of the upper surface of the cavity, h _t is the thickness of the top electrode 1, h _p is the thickness of the piezoelectric material film 2, and h _b is the bottom Electrode 3 thickness. In the embodiment of the present invention, when the first through hole 1-1, the second through hole 2-1 and the third through hole 3-1 are all circular, ignoring the three-dimensional structure of the top electrode lead-out electrode 5 and the bottom electrode lead-out electrode 8 can be It is constructed by rotating the two-dimensional geometric model around the central axis, which is conducive to modeling and simulation. In the embodiment of the present invention, the series resonance frequency f _s and the parallel resonance frequency f _p jointly determine the electromechanical coupling coefficient of the bulk acoustic wave resonator

The size of , using the first-order Taylor approximation formula is expressed as:

In an exemplary example, the embodiment of the present invention obtains the admittance curve based on the parameters of the bulk acoustic wave resonator, and the expression of the piezoelectric equation for obtaining the admittance curve is:

T=cS-eE

D=εE-eS

Among them, T is the stress matrix, c is the piezoelectric material stiffness matrix, S is the strain matrix, e is the piezoelectric stress matrix, E is the electrostatic field strength, D is the electrical displacement, and ε is the piezoelectric material dielectric matrix; The stress matrix e adjusts the resonant frequency and electromechanical coupling coefficient of the bulk acoustic wave resonator, and the piezoelectric stress matrix is:

Among them, e15, e22, e24, e31, e33 are the piezoelectric coefficients of the piezoelectric material in the corresponding directions; based on the above equations, the theoretical admittance curve of the BAW resonator is determined by the method of finite element simulation and the geometric parameters are adjusted; Manufacture the BAW resonator, obtain the actual admittance curve of the BAW resonator, further adjust the geometrical dimensions and process parameters according to the actual admittance curve, and finally determine the geometrical dimensions and process parameters of the BAW resonator that meet the requirements.

In an exemplary example, the first through hole 1-1 in the embodiment of the present invention is any one of the following shapes: circle, ellipse, regular polygon, trapezoid and irregular pentagon;

In an exemplary example, the second through hole 2-1 in the embodiment of the present invention is any one of the following shapes: a circle, an ellipse, a regular polygon, a trapezoid, and an irregular pentagon;

In an exemplary example, the third through hole 3-1 in the embodiment of the present invention is any one of the following shapes: a circle, an ellipse, a regular polygon, a trapezoid and an irregular pentagon.

In an exemplary example, the shape of the outer peripheral contour of the second projection area formed by the projection of the top electrode 1 on the plane where the top of the bottom electrode 3 is located according to the embodiment of the present invention includes any one of the following:

Circles, ellipses, regular polygons, trapezoids, and pentagons. In an exemplary example, the regular polygon according to the embodiment of the present invention includes geometric figures such as an equilateral polygon and a rectangle.

In an exemplary embodiment, the top electrode 1 of the embodiment of the present invention is composed of one or more layers of conductive materials;

In an exemplary example, the conductive material in the embodiment of the present invention includes a conductive compound or any one of the following conductive elements: gold, aluminum, copper, titanium, molybdenum, and platinum.

In an exemplary embodiment, the bottom electrode 3 of the embodiment of the present invention is composed of one or more layers of conductive materials;

In an exemplary example, the conductive material in the embodiment of the present invention includes a conductive compound or any one of the following conductive elements: gold, aluminum, copper, titanium, molybdenum, and platinum.

In an exemplary example, the top electrode 1 in the embodiment of the present invention adopts an aluminum-platinum double-layer electrode. The double-layer electrode deposits aluminum first and then deposits platinum. The platinum is used as an anti-oxidation protective layer to prevent the upper surface of the aluminum layer from being oxidized, thereby improving the device performance. Long-term service reliability;

In an exemplary example, the bottom electrode 3 in the embodiment of the present invention adopts an aluminum-platinum double-layer electrode. The double-layer electrode deposits aluminum first and then deposits platinum. The platinum is used as an anti-oxidation protective layer to prevent the upper surface of the aluminum layer from being oxidized, thereby improving the device performance. The reliability of long-term service; when the upper surface of the bottom electrode 3 is platinum, the quality of the grown aluminum nitride is better.

In an exemplary example, the BAW resonator according to the embodiment of the present invention further includes: a top electrode lead-out electrode 5;

An isolation layer 6 or a cavity 7 is provided between the top electrode lead-out electrode 5 and the piezoelectric material film 2;

Wherein, the isolation layer 6 or the cavity 7 is used to isolate the top electrode lead-out electrode 5 and the piezoelectric material film 2 .

FIG. 7 is a schematic diagram of an isolation layer according to an embodiment of the present invention. As shown in FIG. 7, an isolation layer 6 is provided between the top electrode lead-out electrode 5 and the piezoelectric material film 2, and the isolation layer 6 isolates the top electrode lead-out electrode 5 and the piezoelectric material. Material film 2; In an exemplary embodiment, the isolation layer 6 according to the embodiment of the present invention may be prepared by deposition.

In an exemplary example, the top electrode lead-out electrode 5 according to the embodiment of the present invention is provided with a preset-shaped notch 3-2 at the position of the fourth projection area of the bottom electrode 3;

Wherein, the area of the gap 3-2 includes the fourth projection area.

FIG. 8 is a schematic diagram of a notch in an embodiment of the present invention. As shown in FIG. 8 , a notch 3-2 is provided on the bottom electrode 3; based on the setting of the notch 3-2, the embodiment of the present invention suppresses the top electrode lead-out electrode 5 and the bottom electrode. 3 Spurious modes caused by the coincidence of the projected regions.

In an exemplary embodiment, the bulk acoustic wave resonator of the embodiment of the present invention further includes a top electrode lead-out electrode 5 and a bottom electrode lead-out electrode 8, and an isolation groove 2-2 is etched on the piezoelectric material film 2;

Among them, the projection of the isolation groove 2-2 on the plane where the top of the bottom electrode 3 is located is located in the area composed of the bottom electrode 3 and the bottom electrode lead-out electrode 8; The middle area formed by the outer peripheral contour and the outer peripheral contour of the top electrode 1 .

In an exemplary embodiment, the top electrode 1 and the bottom electrode 3 in the embodiment of the present invention are circular, the isolation groove 2-2 is a fan-shaped ring, the inner radius of the isolation groove 2-2 is larger than the outer radius of the top electrode 1, and the isolation groove The outer radius of 2-2 is smaller than that of the bottom electrode 3 .

FIG. 9 is a schematic diagram of an isolation slot according to an embodiment of the present invention. As shown in FIG. 9 , in the embodiment of the present invention, the isolation slot 2-2 effectively suppresses the propagation of sound waves from the effective area of the bulk acoustic wave resonator to the surroundings, and reduces Interaction between multiple bulk acoustic wave resonators.

In an exemplary embodiment, the bulk acoustic wave resonator of the embodiment of the present invention further includes: a bottom electrode lead-out electrode 8; in an exemplary embodiment, the bulk acoustic wave resonator of the present invention may include more than two top electrode lead-out electrodes 5 and more than two bottom electrode lead-out electrodes 8; FIG. 10 is a schematic diagram of the lead-out electrodes according to the embodiment of the present invention. As shown in FIG. 10, the bulk acoustic wave resonator includes two top electrode lead-out electrodes 5 and two bottom electrode lead-out electrodes 8.

FIG. 11 is a flowchart of a method for preparing a bulk acoustic wave resonator according to an embodiment of the present invention, as shown in FIG. 11 , including:

Step 1101, depositing a bottom electrode material and a bottom electrode lead-out electrode material on the upper surface of the substrate, and performing a patterning process to obtain a bottom electrode lead-out electrode and a bottom electrode including a third through hole;

Step 1102 , preparing a piezoelectric material film on the upper surface of the bottom electrode material; here, the method for preparing the piezoelectric material film includes deposition.

Step 1103, etching the piezoelectric material film to obtain a second through hole;

Step 1104, depositing a top electrode material and a top electrode lead-out electrode material on the upper surface of the piezoelectric material film, and performing a patterning process to obtain a top electrode lead-out electrode and a top electrode including a first through hole;

Step 1105, the corrosive fluid flows to the substrate etching cavity through the first through hole, the second through hole and the third through hole, and releases the bulk acoustic wave resonator;

Wherein, the first projection area of the second through hole on the area delineated by the outer circumference of the top electrode and the overlapping area of the first through hole is the first hollow area; the second through hole is on the area delineated by the outer circumference of the bottom electrode. The overlapping area of the second projection area and the third through hole is the second hollow area.

FIGS. 12 to 16 are finished drawings of the step-by-step preparation of the bulk acoustic wave resonator according to the embodiment of the present invention; as shown in FIG. 12 , the bottom electrode 3 of the bulk acoustic wave resonator obtained by performing step 1101 includes a third through hole 3 in the bottom electrode 3 -1; as shown in Fig. 13, execute the piezoelectric material film 2 of the bulk acoustic wave resonator obtained in step 1102; as shown in Fig. 13, execute step 1103 to etch the piezoelectric material film 2 to form a second through hole 2 -1; as shown in FIG. 14, the top electrode 1 of the bulk acoustic wave resonator obtained by performing step 1104, the top electrode 1 includes a first through hole 1-1; as shown in FIG. 15, performing step 1105 to pass the corrosive fluid through The first through hole, the second through hole and the third through hole flow to the substrate to etch the cavity, releasing the bulk acoustic wave resonator.

In the embodiment of the present invention, the bottom electrode is directly deposited on the substrate to ensure that the thin piezoelectric material can have good crystal plane orientation and low surface roughness; no sacrificial layer process, substrate backside photolithography process and Bragg reflection are required layer, the process is simpler; the vibration of the piezoelectric material film and the electrode at the edge of the resonator is weakened by the substrate, thereby suppressing the parasitic mode; when the first through hole, the second through hole and the third through hole are all circular, The three-dimensional structure of the bulk acoustic wave resonator ignoring the top electrode lead-out electrode and the bottom electrode lead-out electrode can be constructed by rotating a two-dimensional geometric model around the central axis, which is beneficial for modeling and simulation. The embodiment of the present invention can flexibly adjust the area of the upper surface of the cavity of the substrate material to be close to or even smaller than the area of the effective area of the bulk acoustic wave resonator, and ensure the existence of space between adjacent resonators under the condition that the distance between adjacent resonators is extremely small. The area supported by the substrate can effectively alleviate the bending problem of the piezoelectric resonator electrode and the piezoelectric material film in the highly integrated ultra-high frequency filter, thereby improving the electrical characteristics of the resonator and the filter.

"It can be understood by those of ordinary skill in the art that all or some steps in the methods disclosed above, functional modules/units in systems and devices can be implemented as software, firmware, hardware and their appropriate combinations. In the hardware implementation , the division between functional modules/units mentioned in the above description does not necessarily correspond to the division of physical components; for example, one physical component may have multiple functions, or one function or step may be performed cooperatively by several physical components. Some or all components may be implemented as software executed by a processor, such as a digital signal processor or microprocessor, or as hardware, or as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed On computer-readable media, computer-readable media can include computer storage media (or non-transitory media) and communication media (or transitory media). As is known to those of ordinary skill in the art, the term computer storage media is included in the Volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but does not Limited to RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, Digital Versatile Disc (DVD) or other optical disk storage, magnetic cartridges, magnetic tape, magnetic disk storage or other magnetic storage devices, or may be used to store desired information And any other medium that can be accessed by the computer.In addition, it is well known to those of ordinary skill in the art that communication medium usually contains computer readable instructions, data structures, program modules or modulated data signals such as carrier waves or other transport mechanisms. other data, and may include any information delivery medium.".

Claims (11)

1. A bulk acoustic wave resonator, comprising: a top electrode (1), a piezoelectric material film (2), a bottom electrode (3) and a substrate (4); wherein, The top electrode (1) is provided with one or more first through holes (1-1) in the area delineated by the outer peripheral contour, and the piezoelectric material film (2) is provided with one or more second through holes (2-1); the bottom electrode (3) ) is provided with more than one third through hole (3-1) in the area delineated by the outer peripheral contour of the ); Wherein, the first through hole (1-1), the second through hole (2-1) and the third through hole (3-1) are used to etch holes on the substrate (4) The corrosive fluid of the cavity; the first projection area of the second through hole (2-1) on the area delineated by the outer peripheral contour of the top electrode (1) and the first projection area of the first through hole (1-1) The overlapping area is the first hollow area; the second projection area of the second through hole (2-1) on the area delineated by the outer peripheral contour of the bottom electrode (3) and the third through hole (3-1) ) overlapping area is the second hollow area. 2. The bulk acoustic wave resonator according to claim 1, wherein the piezoelectric material film (2) is made up of one or more of the following piezoelectric materials: Aluminum nitride, scandium-doped aluminum nitride, lithium niobate, lithium tantalate, and lead zirconate titanate. 3. The bulk acoustic wave resonator according to claim 1, wherein the projection of the top electrode (1) on the plane where the top of the bottom electrode (3) is located is located on the outer periphery of the bottom electrode (3) within the area delineated by the outline. 4. The bulk acoustic wave resonator according to claim 1, wherein the ratio of the area of the first through hole (1-1) to the area of the area delineated by the outer periphery of the top electrode (1) is the first preset ratio; The ratio of the area of the second through hole (2-1) to the area of the area delineated by the outer peripheral contour of the top electrode (1) is a second preset ratio; The ratio of the area of the third through hole (3-1) to the area of the area delineated by the outer peripheral contour of the top electrode (1) is a third preset ratio; Wherein, the first preset ratio is greater than 0.001 but less than 0.7; the second preset ratio is greater than 0.001 but less than 0.7; the third preset ratio is greater than 0.001 but less than 0.7. 5. The bulk acoustic wave resonator according to claim 1, characterized in that, the area of the upper surface of the cavity on the substrate (4) is the same as the area delineated by the outer circumference of the top electrode (1). The ratio of the area is the fourth preset ratio; Wherein, the fourth preset ratio is greater than 0.8 but less than 4. 6. The bulk acoustic wave resonator according to claim 1, wherein the ratio of the area of the first hollow area to the area of the area delineated by the outer periphery of the top electrode (1) is a fifth preset ratio; The ratio of the area of the second hollow area to the area of the area delineated by the outer peripheral contour of the top electrode (1) is a sixth preset ratio; Wherein, the fifth preset ratio is greater than 0.001 but less than 0.7; the sixth preset ratio is greater than 0.001 but less than 0.7. 7. The bulk acoustic wave resonator according to claim 1, wherein the first through hole (1-1) is any one of the following shapes: circle, ellipse, regular polygon, trapezoid and irregular pentagon; The second through hole (2-1) is any one of the following shapes: circle, ellipse, regular polygon, trapezoid and irregular pentagon; The third through hole (3-1) is any one of the following shapes: circle, ellipse, regular polygon, trapezoid and irregular pentagon. 8. The bulk acoustic wave resonator according to any one of claims 1 to 7, wherein the top electrode (1) is composed of one or more layers of conductive materials; and/or, The bottom electrode (3) is composed of one or more layers of conductive materials. 9. The bulk acoustic wave resonator according to any one of claims 1 to 7, wherein the bulk acoustic wave resonator further comprises a top electrode lead-out electrode (5); An isolation layer (6) or a cavity (7) is provided between the top electrode lead-out electrode (5) and the piezoelectric material film (2); or, The top electrode lead-out electrode (5) is provided with a preset-shaped notch (3-2) at the position of the fourth projection area of the bottom electrode (3); Wherein, the area of the gap (3-2) includes the fourth projection area; the isolation layer (6) or the cavity (7) is used to isolate the top electrode lead-out electrode (5) and the Piezoelectric material film (2). 10. The bulk acoustic wave resonator according to any one of claims 1 to 7, wherein the bulk acoustic wave resonator further comprises a top electrode lead-out electrode (5) and a bottom electrode lead-out electrode (8), the pressure An isolation groove (2-2) is etched on the electrical material film (2); Wherein, the projection of the isolation groove (2-2) on the plane where the top of the bottom electrode (3) is located is located in the area composed of the bottom electrode (3) and the bottom electrode lead-out electrode (8); the isolation The groove (2-2) is located in the middle region formed by the outer peripheral contour of the region composed of the bottom electrode (3) and the bottom electrode lead-out electrode (8) and the outer peripheral contour of the top electrode (1). 11. A preparation method of a bulk acoustic wave resonator, comprising: depositing a bottom electrode material and a bottom electrode lead-out electrode material on the upper surface of the substrate, and performing a patterning process to obtain a bottom electrode lead-out electrode and a bottom electrode including a third through hole; A piezoelectric material film is prepared on the surface of the bottom electrode material; etching the piezoelectric material film to obtain a second through hole; A top electrode material and a top electrode lead-out electrode material are deposited on the upper surface of the piezoelectric material film, and patterned to obtain a top electrode lead-out electrode and a top electrode including a first through hole; The corrosive fluid flows to the substrate etching cavity through the first through hole, the second through hole and the third through hole, and releases the bulk acoustic wave resonator; Wherein, the first projection area of the second through hole on the area delineated by the outer circumference of the top electrode and the overlapping area of the first through hole is the first hollow area; the second through hole is in the bottom electrode The overlapping area of the second projection area and the third through hole on the area delineated by the outer peripheral contour is the second hollow area.

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