CN118264219A - A filter and a method for preparing the same - Google Patents

Abstract

The present application discloses a filter and a preparation method thereof, and relates to the technical field of communication equipment. The preparation method of the filter of the present application comprises forming a plurality of connected resonance units on a substrate and forming a mass load layer on the plurality of resonance units; etching downwardly the mass load layer on a portion of the resonance unit with a first preset thickness to divide the resonance unit into a first type of resonance unit etched with the first preset thickness and a second type of resonance unit not etched with the first preset thickness; etching downwardly a portion of the first type of resonance unit and a portion of the second type of resonance unit with a second preset thickness to divide the first type of resonance unit into a third type of resonance unit and a fourth type of resonance unit, and dividing the second type of resonance unit into a fifth type of resonance unit and a sixth type of resonance unit; patterning the upper electrode layer to form an upper electrode and leading out a lower electrode to form a filter. The filter and the preparation method thereof provided by the present application can reduce the over-etching amount of the piezoelectric layer, thereby improving the performance of the resonator.

Description

A filter and a method for preparing the same

Technical Field

The present application relates to the technical field of communication equipment, and in particular to a filter and a method for preparing the same.

Background technique

Film bulk acoustic wave resonators have become one of the key components for building RF bandpass filters due to their high quality factor, low loss, high reliability, and miniaturization. Generally speaking, a bandpass filter requires two resonators of different frequencies to be cascaded using a certain topological structure, namely a high-frequency series resonator and a low-frequency parallel resonator. Since FBAR mainly uses the energy of longitudinal sound waves to realize the conversion of electrical energy and acoustic energy, the frequency of FBAR is mainly determined by the sandwich thickness of the lower electrode-piezoelectric layer-upper electrode. FBAR can increase the thickness of the sandwich structure layer by adding a mass load layer on the surface of the upper electrode. According to the relationship formula between sound speed-wavelength-frequency, the corresponding frequency can be calculated. The current technical solution for preparing the mass load layer of FBAR is mainly etching technology. First, the mass load layer material is deposited, and then the thin film material is patterned using etching technology.

At present, filters designed based on FBAR not only contain two frequencies, but for complex filters, additional suppression is required for certain frequency bands, so three or even more frequencies are required, which requires multiple deposition and patterning of the mass load layer to achieve this. During each etching, the etching stop time is when the lower material is detected, which means that each etching will be over-etched, that is, when the mass load layer is etched, the piezoelectric layer will be damaged. Although the amount of over-etching is only a few nanometers, if the number of etchings is too many, the damage to the piezoelectric layer will have a cumulative effect. According to the relationship between wavelength and frequency, the thinning of the piezoelectric layer in the outer area of the mass load layer will produce a parasitic mode higher than the series resonance frequency, reducing the effective electromechanical coupling coefficient of the resonator. At the same time, due to the impedance mismatch at the boundary, more pseudo-modes will be generated, which will interfere with the main mode and affect the performance of the resonator.

Summary of the invention

The purpose of the present application is to provide a filter and a method for preparing the same, which can reduce the over-etching amount of the piezoelectric layer, thereby improving the performance of the resonator.

On the one hand, an embodiment of the present application provides a method for preparing a filter, including forming a plurality of connected resonance units on a substrate and forming a mass load layer on the plurality of resonance units, wherein the resonance units include a lower electrode, a piezoelectric layer and an upper electrode layer; etching downwardly a portion of the mass load layer on the resonance unit with a first preset thickness to divide the resonance unit into a first type of resonance unit etched with the first preset thickness and a second type of resonance unit not etched with the first preset thickness; etching downwardly a portion of the first type of resonance unit and a portion of the second type of resonance unit with a second preset thickness to divide the first type of resonance unit into a third type of resonance unit etched with the second preset thickness and a fourth type of resonance unit not etched with the second preset thickness, and dividing the second type of resonance unit into a fifth type of resonance unit etched with the second preset thickness and a sixth type of resonance unit not etched with the second preset thickness; thereby forming mass loads of different thicknesses on each type of resonance unit; patterning the upper electrode layer to form an upper electrode and leading out a lower electrode to form a filter.

As an practicable manner, forming a plurality of connected resonance units on a substrate and forming a mass load layer on the plurality of resonance units includes: forming a plurality of connected resonance units on a substrate; forming a first mass load layer of a second preset thickness on the plurality of resonance units; forming a second mass load layer of a first preset thickness on the first mass load layer, the first mass load layer and the second mass load layer forming a mass load layer.

As an practicable manner, before forming a plurality of connected resonance units on the substrate, the preparation method further includes: forming an acoustic reflection structure in the substrate.

On the other hand, an embodiment of the present application provides a method for preparing a filter, comprising: forming a plurality of connected resonance units on a substrate, wherein the resonance unit comprises a lower electrode, a piezoelectric layer and an upper electrode layer; forming a mass load having a third preset thickness on part of the resonance units by a stripping process, so as to divide the resonance units into a first type of resonance units having a mass load having the third preset thickness and a second type of resonance units having no mass load; forming a mass load having a fourth preset thickness on part of the first type of resonance units and part of the second type of resonance units by a stripping process, so as to divide the first type of resonance units into a third type of resonance units having a mass load having the fourth preset thickness and a fourth type of resonance units having no mass load having the fourth preset thickness, and dividing the second type of resonance units into a fifth type of resonance units having a mass load having the fourth preset thickness and a sixth type of resonance units having no mass load having the fourth preset thickness; and patterning the upper electrode layer to form a plurality of upper electrodes and lead out the lower electrode to form a filter.

As an practicable method, forming a mass load having a third preset thickness on a portion of the resonant unit using a stripping process includes: coating a photoresist on an upper electrode layer and patterning the photoresist; depositing a mass load material having a third preset thickness on the photoresist, so that a portion of the mass load material contacts the upper electrode layer through the patterned photoresist; and stripping the mass load material on the photoresist through the photoresist, so that the mass load material in contact with the upper electrode layer forms a mass load having a third preset thickness.

As an practicable method, forming multiple connected resonant units on a substrate includes: providing a substrate, forming a bottom electrode layer on the substrate and etching to form multiple bottom electrodes; forming a piezoelectric layer on the bottom electrode, the piezoelectric layer covering the bottom electrode; and forming an upper electrode layer on the piezoelectric layer.

As an implementable method, a piezoelectric layer is formed on the bottom electrode. After the piezoelectric layer covers the bottom electrode, the preparation method also includes: etching the piezoelectric layer to form a lead-out hole so that the lower electrode is exposed through the lead-out hole; depositing a conductive material on the piezoelectric layer to form an upper electrode layer, and the conductive material fills the lead-out hole to lead out the lower electrode.

As an implementable method, patterning the upper electrode layer and leading out the lower electrode so that multiple types of resonant units form a filter includes: patterning the upper electrode layer to form multiple upper electrodes so that part of the piezoelectric layer is exposed, and the upper electrodes correspond to the lower electrodes one by one; etching the exposed piezoelectric layer to form lead-out holes, so that the lower electrodes are exposed through the lead-out holes; and depositing a conductive material in the lead-out holes to lead out the lower electrodes.

As an practicable manner, after depositing a conductive material in the lead-out hole to lead out the lower electrode, the preparation method further includes: depositing a passivation material on the upper electrode and patterning to form a passivation layer; depositing a protective layer material on the passivation layer and patterning to form a protective layer.

On the other hand, an embodiment of the present application provides a filter, which is prepared by the above-mentioned filter preparation method, including a substrate and a plurality of resonance units formed on the substrate, and mass loads are respectively arranged on the plurality of resonance units. The plurality of resonance units are divided into multiple types of resonance units according to different thicknesses of the mass loads, and the thicknesses of the mass loads on the multiple types of resonance units are different.

The beneficial effects of the embodiments of the present application include:

The filter preparation method provided by the present application includes forming a plurality of connected resonance units on a substrate and forming a mass load layer on the plurality of resonance units, wherein the resonance unit includes a lower electrode, a piezoelectric layer and an upper electrode layer; etching downwardly a portion of the mass load layer on the resonance unit with a first preset thickness to divide the resonance unit into a first type of resonance unit etched with the first preset thickness and a second type of resonance unit not etched with the first preset thickness; wherein the thickness of the mass load layer on the first type of resonance unit is the original thickness of the mass load layer minus the first preset thickness, and the thickness of the mass load layer on the second type of resonance unit is the original thickness of the mass load layer, and in this process, the etching stop surface is the mass load layer, so that the thickness of the piezoelectric layer will not be affected; etching downwardly a portion of the first type of resonance unit and a portion of the second type of resonance unit with a second preset thickness to divide the first type of resonance unit into a third type of resonance unit etched with the second preset thickness The second type of resonant unit is divided into the fifth type of resonant unit etched with the second preset thickness and the sixth type of resonant unit not etched with the second preset thickness; in this way, mass loads of different thicknesses are formed on each type of resonant unit, wherein the thickness of the mass load layer on the third type of resonant unit is the original thickness minus the sum of the first preset thickness and the second preset thickness, the thickness of the mass load layer on the fourth type of resonant unit is the original thickness minus the first preset thickness, the thickness of the mass load layer on the fifth type of resonant unit is the original thickness minus the second preset thickness, and the thickness of the mass load layer on the sixth type of resonant unit is the original thickness, so as to form mass loads of different thicknesses on different types of resonant units, so that different types of resonant units work at different frequencies; the patterned upper electrode layer forms the upper electrode and leads out the lower electrode to form a filter, and the etching stops at the piezoelectric layer when the upper electrode layer is patterned. Therefore, in the preparation method of the filter provided in the embodiment of the present application, only when the upper electrode layer is patterned, it stops on the piezoelectric layer, thereby reducing the over-etching amount of the piezoelectric layer and improving the performance of the resonator.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

FIG1 is a flow chart of a method for preparing a filter provided in an embodiment of the present application;

FIG. 2 is one of the state diagrams of a method for preparing a filter provided in an embodiment of the present application;

FIG3 is a second state diagram of a method for preparing a filter provided in an embodiment of the present application;

FIG4 is a third state diagram of a method for preparing a filter provided in an embodiment of the present application;

FIG5 is a fourth state diagram of a method for preparing a filter provided in an embodiment of the present application;

FIG6 is a fifth state diagram of a method for preparing a filter provided in an embodiment of the present application;

FIG. 7 is a sixth state diagram of a method for preparing a filter provided in an embodiment of the present application;

FIG8 is a seventh state diagram of a method for preparing a filter provided in an embodiment of the present application;

FIG9 is an eighth state diagram of a method for preparing a filter provided in an embodiment of the present application;

FIG10 is a ninth state diagram of a method for preparing a filter provided in an embodiment of the present application;

FIG11 is a tenth state diagram of a method for preparing a filter provided in an embodiment of the present application;

FIG12 is a state diagram eleven of a method for preparing a filter provided in an embodiment of the present application;

FIG13 is a twelve state diagram of a method for preparing a filter provided in an embodiment of the present application;

FIG14 is a thirteenth state diagram of a method for preparing a filter provided in an embodiment of the present application;

FIG15 is a fourteenth state diagram of a method for preparing a filter provided in an embodiment of the present application;

FIG16 is a fifteenth state diagram of a method for preparing a filter provided in an embodiment of the present application;

FIG17 is a sixteenth state diagram of a method for preparing a filter provided in an embodiment of the present application;

FIG18 is a second flow chart of a method for preparing a filter provided in an embodiment of the present application;

FIG19 is a seventeenth state diagram of a method for preparing a filter provided in an embodiment of the present application;

FIG20 is a state diagram of the eighteenth method for preparing a filter provided in an embodiment of the present application;

FIG21 is a nineteenth state diagram of a method for preparing a filter provided in an embodiment of the present application;

FIG. 22 is a state diagram 20 of a method for preparing a filter provided in an embodiment of the present application;

FIG. 23 is a state diagram 21 of a method for preparing a filter provided in an embodiment of the present application;

FIG. 24 is a state diagram 22 of a method for preparing a filter provided in an embodiment of the present application;

FIG. 25 is a state diagram 23 of a method for preparing a filter provided in an embodiment of the present application;

FIG. 26 is a state diagram 24 of a method for preparing a filter provided in an embodiment of the present application;

FIG. 27 is a state diagram 25 of a method for preparing a filter provided in an embodiment of the present application;

FIG. 28 is a state diagram 26 of a method for preparing a filter provided in an embodiment of the present application;

FIG29 is a state diagram 27 of a method for preparing a filter provided in an embodiment of the present application;

FIG30 is a state diagram 28 of a method for preparing a filter provided in an embodiment of the present application;

FIG31 is a state diagram 29 of a method for preparing a filter provided in an embodiment of the present application;

FIG32 is a state diagram of the 30th method for preparing a filter provided in an embodiment of the present application;

FIG33 is a state diagram 31 of a method for preparing a filter provided in an embodiment of the present application;

FIG34 is a state diagram 32 of a method for preparing a filter provided in an embodiment of the present application;

FIG35 is one of the structural schematic diagrams of a mask provided in an embodiment of the present application;

FIG36 is a second schematic diagram of the structure of a mask provided in an embodiment of the present application;

FIG. 37 is a third schematic diagram of the structure of a mask provided in an embodiment of the present application.

Icon: 110-substrate; 120-resonance unit; 122-lower electrode; 123-piezoelectric layer; 124-upper electrode layer; 125-upper electrode; 126-lead-out hole; 130-mass load layer; 141-first type of resonant unit; 142-second type of resonant unit; 143-third type of resonant unit; 144-fourth type of resonant unit; 145-fifth type of resonant unit; 146-sixth type of resonant unit; 151-seed layer; 152-passivation layer; 153-protective layer; 154-groove; 155-sacrificial material; 156-cavity; 161-release hole; 171-effective resonant region; 172-ineffective resonant region.

Detailed ways

In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not require further definition and explanation in the subsequent drawings.

The present application provides a method for preparing a filter, as shown in FIG1 , comprising:

S10: As shown in FIG. 2 to FIG. 9 , a plurality of connected resonance units 120 are formed on the substrate 110 and a mass load layer 130 is formed on the plurality of resonance units 120 , wherein the resonance unit 120 includes a lower electrode 122 , a piezoelectric layer 123 and an upper electrode layer 124 .

Among them, the upper electrode 125, the lower electrode 122 and the piezoelectric layer 123 have a partially overlapping active area projected in the hierarchical direction, the lower electrode 122 is multiple corresponding to each resonance unit 120, the piezoelectric layers 123 of the multiple resonance units 120 are connected as a whole, the upper electrode layer 124 of the multiple resonance units 120 is the entire hierarchical structure laid on the piezoelectric layer 123, and a whole layer of mass load layer 130 is formed on the upper electrode layer 124.

S20: As shown in FIG. 10 , the mass load layer 130 on a portion of the resonance unit 120 is etched downward by a first preset thickness to divide the resonance unit 120 into a first type of resonance unit 141 etched by the first preset thickness and a second type of resonance unit 142 not etched by the first preset thickness.

Among them, the thickness of the mass load layer 130 on the first type of resonance unit 141 is the original thickness of the mass load layer 130 minus the first preset thickness, and the thickness of the mass load layer 130 on the second type of resonance unit 142 is the original thickness of the mass load layer 130. In this process, the etching stop surface is the mass load layer 130, so that the thickness of the piezoelectric layer 123 will not be affected.

S30: As shown in FIG. 11 , a portion of the first type resonant unit 141 and a portion of the second type resonant unit 142 are etched downward with a second preset thickness, so as to divide the first type resonant unit 141 into a third type resonant unit 143 etched with the second preset thickness and a fourth type resonant unit 144 not etched with the second preset thickness, and divide the second type resonant unit 142 into a fifth type resonant unit 145 etched with the second preset thickness and a sixth type resonant unit 146 not etched with the second preset thickness; thereby forming mass loads of different thicknesses on each type of resonant unit 120;

The thickness of the mass load layer 130 on the third type of resonance unit 143 is the original thickness minus the sum of the first preset thickness and the second preset thickness, the thickness of the mass load layer 130 on the fourth type of resonance unit 144 is the original thickness minus the first preset thickness, the thickness of the mass load layer 130 on the fifth type of resonance unit 145 is the original thickness minus the second preset thickness, and the thickness of the mass load layer 130 on the sixth type of resonance unit 146 is the original thickness, so that different types of resonance units 120 operate at different frequencies.

In this process, the etching stop surface is the mass load layer 130 or the upper electrode layer 124 , so that the thickness of the piezoelectric layer 123 is not affected.

S40 : As shown in FIGS. 12 , 13 and 14 , the upper electrode layer 124 is patterned to form an upper electrode 125 and the lower electrode 122 is led out to form a filter.

When patterning the upper electrode layer 124, etching stops at the piezoelectric layer 123. Therefore, in the filter manufacturing method provided in the embodiment of the present application, etching stops at the piezoelectric layer 123 only when patterning the upper electrode 125, thereby reducing the overetching amount of the piezoelectric layer 123 and improving the performance of the resonator.

It should be noted that the embodiment of the present application is described by taking two downward etchings as an example, and does not limit the present application to etching only twice to form four mass loads of different thicknesses. When etching downwards three times, six mass loads of different thicknesses can be formed, and by analogy, multiple resonance units 120 of different frequencies can be completed.

Each time etching is performed downward, a mask is required, so by using N masks, n*(n-1) resonance units 120 with different resonance frequencies can be prepared, thus saving processing costs.

The preparation method of the filter provided in the present application includes forming a plurality of connected resonance units 120 on a substrate 110 and forming a mass load layer 130 on the plurality of resonance units 120; etching downwardly a portion of the mass load layer 130 on the resonance unit 120 with a first preset thickness, and dividing the resonance unit 120 into a first type of resonance unit 141 etched with the first preset thickness and a second type of resonance unit 142 not etched with the first preset thickness; wherein the thickness of the mass load layer 130 on the first type of resonance unit 141 is the original thickness of the mass load layer 130 minus the first preset thickness, and the thickness of the mass load layer 130 on the second type of resonance unit 142 is the original thickness of the mass load layer 130, and in this process, the etching stop surface is the mass load layer 130, so that the thickness of the piezoelectric layer 123 is not affected; then etching downwardly a portion of the first type of resonance unit 141 and a portion of the second type of resonance unit 142 with a second preset thickness, so as to divide the first type of resonance unit 141 into a third type of resonance unit 141 etched with the second preset thickness. The resonant unit 143 and the fourth type of resonant unit 144 which is not etched to the second preset thickness, divide the second type of resonant unit 142 into the fifth type of resonant unit 145 which is etched to the second preset thickness and the sixth type of resonant unit 146 which is not etched to the second preset thickness; thereby, mass loads of different thicknesses are formed on each type of resonant unit 120, wherein the thickness of the mass load layer 130 on the third type of resonant unit 143 is the original thickness minus the sum of the first preset thickness and the second preset thickness, the thickness of the mass load layer 130 on the fourth type of resonant unit 144 is the original thickness minus the first preset thickness, the thickness of the mass load layer 130 on the fifth type of resonant unit 145 is the original thickness minus the second preset thickness, and the thickness of the mass load layer 130 on the sixth type of resonant unit 146 is the original thickness, so that different types of resonant units 120 operate at different frequencies; the patterned upper electrode layer 124 forms the upper electrode 125 and leads out the lower electrode 122 to form a filter, and the etching stops at the piezoelectric layer 123 when the upper electrode layer 124 is patterned. Therefore, in the method for preparing the filter provided in the embodiment of the present application, the patterning stops on the piezoelectric layer 123 only when the upper electrode 125 is patterned, thereby reducing the over-etching amount of the piezoelectric layer 123 and improving the performance of the resonator.

Optionally, forming a plurality of connected resonance units 120 on the substrate 110 and forming a mass load layer 130 on the plurality of resonance units 120 includes:

S11: As shown in FIG. 2 to FIG. 9 , a plurality of connected resonance units 120 are formed on a substrate 110 ;

S12: As shown in FIG. 9 , a first mass load layer having a second preset thickness is formed on the plurality of resonance units 120 ;

S13 : as shown in FIG. 9 , a second mass load layer with a first preset thickness is formed on the first mass load layer. The first mass load layer and the second mass load layer form a mass load layer 130 .

The mass load layer 130 is divided into a first mass load layer and a second mass load layer for deposition. The first mass load layer is close to the resonance unit 120 and has a second preset thickness. The second mass load layer is far away from the resonance unit 120 and has a first preset thickness. In this way, when etching downward for the first time, it is easier to stop etching at the interface between the first mass load layer and the second mass load layer.

The thickness of the first mass-loading layer and the second mass-loading layer may be the same or different; the materials of the first mass-loading layer and the second mass-loading layer may be the same or different.

In one achievable manner of the embodiment of the present application, before forming a plurality of connected resonance units 120 on the substrate 110, the preparation method further includes:

S01 : forming an acoustic reflection structure in the substrate 110 .

Specifically, the structure of the sound reflection structure is not limited in the embodiment of the present application, and can be a cavity 156, or a stack of materials with high and low sound reflection coefficients alternately arranged. For example, when the sound reflection structure is a cavity 156, the following steps are used to form it:

As shown in FIG. 2 , a substrate 110 is provided. The specific material of the substrate 110 is not limited in the embodiment of the present application, and it may be a high-resistance silicon substrate 110 ;

As shown in FIG. 3 , a groove 154 is etched on the substrate 110 at a position corresponding to the resonant unit 120 , and as shown in FIG. 4 , a sacrificial material 155 is filled in the groove 154 ;

As shown in FIG5 , chemical mechanical polishing is used to grind the surface of the substrate 110 to the surface of the high-resistance silicon substrate 110 ;

As shown in FIG6 , a seed layer 151 is deposited on the surface of the high-resistance silicon substrate 110 to improve the film quality of the piezoelectric layer 123 ;

After the preparation of the resonance unit 120 and the mass load is completed, a release hole 161 can be etched to form as shown in Figures 16 and 33, and the sacrificial material 155 in the groove 154 can be released through the release hole 161 to form a cavity 156 as shown in Figures 17 and 34.

Another aspect of the present application provides a method for preparing a filter, as shown in FIG18 , comprising:

S10′: as shown in FIGS. 19 to 27 , a plurality of connected resonance units 120 are formed on the substrate 110 , wherein the resonance unit 120 includes a lower electrode 122 , a piezoelectric layer 123 and an upper electrode layer 124 ;

S20': as shown in FIG. 28 , a mass load having a third preset thickness is formed on part of the resonance unit 120 by a stripping process, so as to divide the resonance unit 120 into a first type of resonance unit 141 having a mass load having the third preset thickness and a second type of resonance unit 142 having no mass load;

S30': as shown in FIG. 29 , a mass load having a fourth preset thickness is formed on part of the first type resonance unit 141 and part of the second type resonance unit 142 by a stripping process, so as to divide the first type resonance unit 141 into a third type resonance unit 143 having a mass load having a fourth preset thickness and a fourth type resonance unit 144 having no mass load having a fourth preset thickness, and divide the second type resonance unit 142 into a fifth type resonance unit 145 having a mass load having a fourth preset thickness and a sixth type resonance unit 146 having no mass load having a fourth preset thickness;

S40': As shown in FIG30, the upper electrode layer 124 is patterned to form a plurality of upper electrodes 125 and the lower electrode 122 is led out to form a filter.

The embodiment of the present application uses a stripping process to form a mass load on the upper electrode layer 124. In the stripping process, the etching of the material is not included, thereby avoiding the etching of the piezoelectric layer 123. The process only stops on the piezoelectric layer 123 when patterning the upper electrode 125, thereby reducing the over-etching amount of the piezoelectric layer 123 and improving the performance of the resonator.

Optionally, forming a mass load having a third preset thickness on a portion of the resonance unit 120 by using a stripping process includes:

S21': coating a photoresist on the upper electrode layer 124 and patterning the photoresist;

S22′: depositing a mass load material of a third preset thickness on the photoresist, so that a portion of the mass load material contacts the upper electrode layer 124 through the patterned photoresist;

S23': stripping the mass load material on the photoresist through the photoresist, so that the mass load material in contact with the upper electrode layer 124 forms a mass load with a third preset thickness.

During the process of patterning the photoresist, the piezoelectric layer 123 is not damaged, thereby avoiding the situation where the thickness of the piezoelectric layer 123 inside/outside the active area is inconsistent due to over-etching.

In one achievable manner of the embodiment of the present application, forming a plurality of connected resonance units 120 on the substrate 110 includes:

S111: As shown in FIGS. 2 and 7 , and FIGS. 19 and 24 , providing a substrate 110 , forming a bottom electrode layer on the substrate 110 and etching to form a plurality of bottom electrodes;

S112: As shown in FIG8 and FIG25 , a piezoelectric layer 123 is formed on the bottom electrode, and the piezoelectric layer 123 covers the bottom electrode;

S113 : As shown in FIG. 9 and FIG. 27 , an upper electrode layer 124 is formed on the piezoelectric layer 123 .

Optionally, after a piezoelectric layer 123 is formed on the bottom electrode and the piezoelectric layer 123 covers the bottom electrode, the preparation method further includes:

S1121: as shown in FIG. 26 , the piezoelectric layer 123 is etched to form an extraction hole 126 , so that the lower electrode 122 is exposed through the extraction hole 126 ;

S1122 : As shown in FIG. 27 , a conductive material is deposited on the piezoelectric layer 123 to form an upper electrode layer 124 , and the conductive material fills the lead-out hole 126 to lead out the lower electrode 122 .

In one achievable manner of the embodiment of the present application, patterning the upper electrode layer 124 and leading out the lower electrode 122 so that the multiple types of resonance units 120 form a filter includes:

S41: As shown in FIG. 12 , patterning the upper electrode layer 124 to form a plurality of upper electrodes 125 so that a portion of the piezoelectric layer 123 is exposed, and the upper electrodes 125 correspond to the lower electrodes 122 one by one;

S42: as shown in FIG. 13 , etching the exposed piezoelectric layer 123 to form a lead-out hole 126 , so that the lower electrode 122 is exposed through the lead-out hole 126 ;

S43 : As shown in FIG. 13 , a conductive material is deposited in the lead-out hole 126 to lead out the lower electrode 122 .

Optionally, after depositing a conductive material in the lead-out hole 126 to lead out the lower electrode 122, the preparation method further includes:

S44: As shown in FIG. 14 and FIG. 31 , a passivation material is deposited on the upper electrode 125 and patterned to form a passivation layer 152 ; the passivation layer 152 is used to passivate the surface of the upper electrode 125 and the piezoelectric layer 123 to prevent the upper electrode 125 and the piezoelectric layer 123 from reacting with the environment, thereby improving the stability of the filter.

S45: As shown in FIG15 and FIG32, a protective layer 153 material is deposited on the passivation layer 152 and patterned to form the protective layer 153. The protective layer 153 is used to protect the filter and prevent the filter from being damaged by external collision.

The embodiment of the present application adopts two methods, namely, etching downward step by step and stacking upward step by step, to form mass loads of different thicknesses. Since the etching positions of the two methods are the same during the implementation of the scheme, the same set of masks can be used, making the preparation method of the filter more flexible and saving costs. Specifically, as shown in Figures 35, 36 and 37, the effective resonance area 171 of the first mass load layer and the second mass load layer is light-transmissive, and the ineffective resonance area 172 is light-shielding. When etching downward step by step, the material therein is etched, and when stacking upward step by step, the material therein is retained. Finally, the thickness of the mass load layer 130 at different positions is ensured by the etching process of the upper electrode layer 124, so as to achieve the adjustment of the frequency of the resonance unit 120.

On the other hand, an embodiment of the present application provides a filter, which is prepared by the above-mentioned filter preparation method, including a substrate 110 and a plurality of resonance units 120 formed on the substrate 110, and the plurality of resonance units 120 are respectively provided with mass loads. The plurality of resonance units 120 are divided into multiple types of resonance units 120 according to different thicknesses of the mass loads, and the thicknesses of the mass loads on the multiple types of resonance units 120 are different.

The filter provided in the present application is prepared by the filter preparation method described above, which effectively avoids the phenomenon of over-etching of the piezoelectric layer 123 and avoids the filter performance being affected by the etching of the mass load layer 130 .

The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (11)

1. A method of manufacturing a filter, comprising:

Forming a plurality of connected resonance units on a substrate and forming a mass loading layer on the plurality of resonance units, wherein the resonance units comprise a lower electrode, a piezoelectric layer and an upper electrode layer;

Etching part of the mass load layer on the resonance unit downwards with a first preset thickness so as to divide the resonance unit into a first type resonance unit etched with the first preset thickness and a second type resonance unit not etched with the first preset thickness;

Etching part of the first type resonance units and part of the second type resonance units downwards with a second preset thickness so as to divide the first type resonance units into third type resonance units with the second preset thickness and fourth type resonance units without the second preset thickness, and dividing the second type resonance units into fifth type resonance units with the second preset thickness and sixth type resonance units without the second preset thickness; thereby forming mass loads of different thickness on each type of the resonance units;

the upper electrode layer is patterned to form an upper electrode and a lower electrode is drawn out so that a filter is formed.

2. The method of manufacturing a filter according to claim 1, wherein forming a plurality of connected resonance units on a substrate and forming a mass-loaded layer on a plurality of the resonance units comprises:

Forming a plurality of connected resonant cells on a substrate;

Forming a first mass loading layer with a second preset thickness on a plurality of the resonance units;

And forming a second mass loading layer with a first preset thickness on the first mass loading layer, wherein the first mass loading layer and the second mass loading layer form a mass loading layer.

3. The method of manufacturing a filter according to claim 2, wherein before forming a plurality of connected resonance units on the substrate, the method further comprises:

An acoustic reflective structure is formed in the substrate.

4. A method of manufacturing a filter, comprising:

Forming a plurality of connected resonance units on a substrate, wherein the resonance units comprise a lower electrode, a piezoelectric layer and an upper electrode layer;

Forming a mass load with a third preset thickness on part of the resonance units by adopting a stripping process so as to divide the resonance units into a first type resonance unit with the third preset thickness mass load and a second type resonance unit without the mass load;

forming a mass load with a fourth preset thickness on part of the first type of resonance units and part of the second type of resonance units by adopting a stripping process, so as to divide the first type of resonance units into a third type of resonance units with the fourth preset thickness mass load and a fourth type of resonance units without the fourth preset thickness mass load, and divide the second type of resonance units into a fifth type of resonance units with the fourth preset thickness mass load and a sixth type of resonance units without the fourth preset thickness mass load;

the upper electrode layer is patterned to form a plurality of upper electrodes and a lower electrode is drawn out so that a filter is formed.

5. The method of manufacturing a filter according to claim 4, wherein forming a mass load having a third predetermined thickness on a part of the resonance units using a lift-off process comprises:

coating photoresist on the upper electrode layer and patterning the photoresist;

depositing a third preset thickness of mass loading material on the photoresist, so that part of the mass loading material is contacted with the upper electrode layer through the patterned photoresist;

And stripping the mass-loaded material on the photoresist through the photoresist, so that the mass-loaded material contacted with the upper electrode layer forms a mass load with a third preset thickness.

6. The method of manufacturing a filter according to claim 1 or 4, wherein the forming a plurality of connected resonance units on the substrate includes:

providing a substrate, forming a bottom electrode layer on the substrate and etching to form a plurality of bottom electrodes;

Forming a piezoelectric layer on the bottom electrode, the piezoelectric layer covering the bottom electrode;

an upper electrode layer is formed on the piezoelectric layer.

7. The method of manufacturing a filter according to claim 6, wherein the forming a piezoelectric layer on the bottom electrode, the method further comprises, after the piezoelectric layer covers the bottom electrode:

Etching the piezoelectric layer to form a lead-out hole, so that the lower electrode is exposed through the lead-out hole;

And depositing a conductive material on the piezoelectric layer to form an upper electrode layer, wherein the conductive material fills the extraction holes to extract the lower electrode.

8. The method of manufacturing a filter according to claim 1 or 4, wherein patterning the upper electrode layer and extracting the lower electrode so that a plurality of types of resonance units form the filter comprises:

patterning the upper electrode layer to form a plurality of upper electrodes so that part of the piezoelectric layers are exposed, wherein the upper electrodes correspond to the lower electrodes one by one;

Etching the exposed piezoelectric layer to form an extraction hole, so that the lower electrode is exposed through the extraction hole;

a conductive material is deposited in the extraction holes to extract the lower electrode.

9. The method of manufacturing a filter according to claim 8, wherein after depositing a conductive material in the extraction hole to extract the lower electrode, the method further comprises:

depositing a passivation material on the upper electrode and patterning to form a passivation layer;

A protective layer material is deposited and patterned on the passivation layer to form a protective layer.

10. A filter prepared by the method for preparing a filter according to any one of claims 1 to 3, comprising a substrate and a plurality of resonance units formed on the substrate, wherein the plurality of resonance units are respectively provided with a mass load, the plurality of resonance units are divided into a plurality of types of resonance units according to different thicknesses of the mass loads, and the thicknesses of the mass loads on the plurality of types of resonance units are different.

11. A filter prepared by the method for preparing a filter according to any one of claims 4 to 9, comprising a substrate and a plurality of resonance units formed on the substrate, wherein the plurality of resonance units are respectively provided with a mass load, the plurality of resonance units are divided into a plurality of types of resonance units according to different thicknesses of the mass loads, and the thicknesses of the mass loads on the plurality of types of resonance units are different.