CN112039491B - Thin film piezoelectric acoustic wave filter and manufacturing method thereof - Google Patents
Thin film piezoelectric acoustic wave filter and manufacturing method thereof Download PDFInfo
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Abstract
The invention discloses a film piezoelectric acoustic wave filter and a manufacturing method thereof, wherein the film piezoelectric acoustic wave filter comprises: a first substrate; a plurality of acoustic resonator units disposed on the first substrate, each of the acoustic resonator units including a piezoelectric sensing sheet, a first electrode and a second electrode facing each other for applying a voltage to the piezoelectric sensing sheet; the cover cap layer is positioned on the first substrate and at least surrounds two acoustic wave resonator units so as to form a first cavity between the acoustic wave resonator units and the cover cap layer; the cap layer comprises: the cap layer body is provided with a release hole with a set aperture, and the capping layer seals the release hole, and part of the capping layer is embedded into part of the release hole. The invention can solve the problems that the reliability of the packaging process of the upper cavity is low and the material of the sealing cover layer enters the cavity.
Description
Technical Field
The invention relates to the field of semiconductor device manufacturing, in particular to a thin film piezoelectric acoustic wave filter and a manufacturing method thereof.
Background
With the development of wireless communication technology, the traditional single-band single-standard equipment cannot meet the requirement of diversification of communication systems. Currently, communication systems are increasingly moving towards multiple frequency bands, which requires that communication terminals can accept each frequency band to meet the requirements of different communication service providers and different regions.
RF (radio frequency) filters are typically used to pass or block particular frequencies or frequency bands in RF signals. In order to meet the development requirements of wireless communication technology, an RF filter used in a communication terminal is required to meet the requirements of multiband and multi-system communication technologies, and meanwhile, the RF filter in the communication terminal is required to be continuously developed in the direction of miniaturization and integration, and one or more RF filters are adopted in each frequency band.
The most important metrics for an RF filter include quality factor Q and insertion loss. As the frequency difference between different frequency bands becomes smaller and smaller, the RF filter needs to have very good selectivity to pass signals in the frequency band and to block signals outside the frequency band. The larger the Q value, the narrower the passband bandwidth can be achieved by the RF filter, resulting in better selectivity.
In the manufacturing process of the resonator, a cavity needs to be formed above the acoustic transducer in the resonator, so that the sound wave in the resonator can propagate without interference, and the performance and the function of the filter meet the requirements. Currently, a package for implementing a resonator is mainly formed through a packaging process, and a cavity is formed at the same time, and the cavity can simultaneously accommodate a plurality of acoustic transducers, for example, a metal cap technology, a chip-scale SAW package (CSSP) technology, a chip-scale SAW package (DSSP) technology, or the like. However, the packaging process is more complex and the process reliability is lower.
Taking the metal cap technology as an example, the metal cap technology fixes a metal cover on a substrate, so that the metal cover and the substrate enclose a cavity, and the cavity is used for accommodating an acoustic transducer. The metal cap is usually fixed to the substrate by dispensing or plating tin. When the dispensing mode is adopted, the adhesive adopted by the dispensing process is easy to flow into the cavity before curing, so that the acoustic transducer is influenced; when the tin plating mode is adopted, the melted tin can easily flow to the cavity in the reflow soldering process. Both of the above conditions are prone to failure of the resonator. In addition, the method has high requirements on the flatness of the substrate and the metal cover, the bonding force between the metal cover and the substrate is poor, and the tightness of the cavity is difficult to ensure, so that the reliability and the performance consistency of the resonator are reduced.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the packaging process for forming the upper cavity of the film piezoelectric acoustic wave filter in the prior art has low reliability, and the material of the capping layer enters the cavity.
In order to achieve the above object, the present invention provides a thin film piezoelectric acoustic wave filter including:
a first substrate;
a plurality of acoustic resonator units disposed on the first substrate, each of the acoustic resonator units including a piezoelectric sensing sheet, a first electrode and a second electrode facing each other for applying a voltage to the piezoelectric sensing sheet;
the cover cap layer is positioned on the first substrate and at least surrounds two acoustic wave resonator units so as to form a first cavity between the acoustic wave resonator units and the cover cap layer;
the cap layer comprises: the cap layer body is provided with a release hole with a set hole diameter, and the capping layer is used for sealing the release hole and is partially embedded into part of the release hole.
The invention also provides a manufacturing method of the film piezoelectric acoustic wave filter, which comprises the following steps:
providing a first substrate;
forming a plurality of acoustic wave resonator units on the first substrate, each acoustic wave resonator unit including a piezoelectric sensing sheet body, a first electrode and a second electrode which are used for applying a voltage to the piezoelectric sensing sheet body and are opposite to each other;
forming a sacrificial layer on at least two acoustic wave resonator units and a spacing region between the acoustic wave resonator units;
forming a cap layer body to cover the sacrificial layer;
forming a release hole on the cap layer body, and removing the sacrificial layer through the release hole to form a first cavity;
and forming a cover layer on the cover cap layer body, and partially embedding the cover layer into the release hole to seal the release hole.
The invention has the beneficial effects that:
the cap layer of the film piezoelectric acoustic wave filter surrounds at least two acoustic wave resonator units, and the first cavity has relatively large volume, so that the release of a sacrificial layer in the manufacturing process is facilitated, the process compatibility is improved, and the process difficulty is reduced; the plurality of acoustic wave resonators share one cap layer, so that the flexibility of position selection of the release hole is increased. The acoustic wave resonator units as a whole can be better connected in series or in parallel.
Furthermore, the filter comprises a plurality of acoustic wave resonator units, and the acoustic wave resonator units are at least distributed in the two first cavities, so that the volume of the cavities is not too large, the requirement on the supporting strength of the cap layer can be balanced, the increase of the height of the cavities and the thickness of the cap layer is relieved, and the volume of the filter can be better controlled.
The thin-film piezoelectric acoustic wave filter has high process reliability by forming the sacrificial layer, releasing the sacrificial layer by using the release hole after forming the cap layer body, and sealing the release hole by using the capping layer. The release holes with the apertures are set, so that the sealing cover layer at the release holes is embedded into the release holes, the sealing cover layer can tightly seal the release holes, and the bonding strength of the sealing cover layer and the cap layer is increased; in the process of forming the capping layer, the material of the capping layer is embedded into part of the release holes and does not enter the first cavity, so that the performance of the filter can be obviously improved, and the structural strength of the capping layer body can be increased.
Further, the design of the release hole in the cap layer body needs to compromise the strength of the release effect of the sacrificial layer and the whole cap layer, the aperture size range is between 0.1um to 3um, the density range is 1 to 100 per 100 square microns and is unequal, so that the subsequent capping layer can be ensured to be well sealed to the release hole, the release efficiency of the sacrificial layer can be ensured, and when the capping layer is utilized to seal the release hole, the material of the capping layer can be ensured not to enter the first cavity to influence the performance of the acoustic wave resonator unit.
Further, the thickness scope of cap layer body is 5um to 50um, the thickness scope of capping layer is 5um to 50um, and the thickness of cap layer body and capping layer can each other be supplementary, and the gross thickness can be 10um to 100um, according to the nimble adjustment of the demand of resistant mould pressing, under the same thickness, the resistant mould pressing ability that the cap layer of this scheme is than the independent cap that only has organic curing membrane is showing and is strengthening.
Drawings
Fig. 1 is a schematic structural diagram of a thin film piezoelectric acoustic wave filter according to embodiment 1 of the present invention.
Fig. 2 to 8 are schematic structural diagrams corresponding to different steps in a manufacturing process of a method for manufacturing a thin film piezoelectric acoustic wave filter according to embodiment 2 of the present invention.
Description of reference numerals:
10-a first substrate; 11-a first dielectric layer; 12-a bragg reflective layer; 20-a lower electrode; 21-piezoelectric induction sheet body; 22-an upper electrode; 24-an electrode interconnect wafer; 300-cap body; 31-a release aperture; 302-a capping layer; 50-a sacrificial layer; 23-first cavity.
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples. The advantages and features of the present invention will become more apparent from the following description and drawings, it being understood, however, that the concepts of the present invention may be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. The drawings are in simplified form and are not to scale, but are provided for convenience and clarity in describing embodiments of the invention.
It will be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it can be directly on, adjacent to, connected or coupled to the other elements or layers or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to" or "directly coupled to" other elements or layers, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.
Spatial relational terms such as "under," "below," "under," "above," "over," and the like may be used herein for convenience in describing the relationship of one element or feature to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, then elements or features described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary terms "under" and "under" can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatial descriptors used herein interpreted accordingly.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of the associated listed items.
If the method herein comprises a series of steps, the order in which these steps are presented herein is not necessarily the only order in which these steps may be performed, and some steps may be omitted and/or some other steps not described herein may be added to the method. Although elements in one drawing may be readily identified as such in other drawings, the present disclosure does not identify each element as being identical to each other in every drawing for clarity of description.
Example 1
Fig. 1 is a schematic structural diagram of a thin-film piezoelectric acoustic wave filter according to an embodiment of the present invention, in which only two acoustic resonator units are shown, and the number of the acoustic resonator units in each filter and the electrical connection manner between the acoustic resonator units are specifically set according to the requirements of the filter itself.
Referring to fig. 1, the thin film piezoelectric acoustic wave filter includes:
a first substrate; a plurality of acoustic wave resonator units disposed on the first substrate; the acoustic wave resonator units are minimum resonance units, each acoustic wave resonator unit includes a piezoelectric sensing sheet body 21, and a first electrode and a second electrode (in this embodiment, the acoustic wave resonator unit is a bulk acoustic wave resonator unit, the first electrode is an upper electrode 22, the second electrode is a lower electrode 20, when the acoustic wave resonator unit is a surface acoustic wave resonator unit, the first electrode and the second electrode are cap layers on the first substrate, respectively, a first interdigital transducer and a second interdigital transducer on the piezoelectric sensing sheet body, and the cap layers surround at least two acoustic wave resonator units, so as to form a first cavity 23 between the acoustic wave resonator unit and the cap layers. The cap layer comprises: a cap body 300 having a release hole 31 with a predetermined aperture, and a capping layer 302 sealing the release hole 31, wherein a portion of the capping layer 302 is embedded in a portion of the release hole 31.
The first substrate is used for carrying the acoustic wave resonator unit, and in this embodiment, the first substrate includes a first substrate 10 and a first dielectric layer 11 located on the first substrate 10, and an acoustic wave reflection structure is disposed in the first dielectric layer 11, where the acoustic wave reflection structure may be a second cavity or a bragg reflection layer. In this embodiment, a bragg reflection layer 12 is disposed in the first dielectric layer 11, and the acoustic wave resonator unit is located in a region surrounded by the bragg reflection layer 12. When the acoustic wave reflection structure is a second cavity, the edge of the acoustic wave resonator unit is located in the area enclosed by the second cavity.
The first substrate is provided with a plurality of acoustic wave resonator units, and the acoustic wave resonator units can be bulk acoustic wave resonator units or surface acoustic wave resonator units. In this embodiment, the acoustic wave resonator unit is a bulk acoustic wave resonator unit, the bulk acoustic wave resonator unit includes, from bottom to top, a lower electrode 20, a piezoelectric sensing sheet 21, and an upper electrode 22 that are stacked, and an area where the lower electrode 20, the piezoelectric sensing sheet 21, and the upper electrode 22 are overlapped with each other in a direction perpendicular to the first substrate is defined as an effective resonance area. In the invention, along the direction vertical to the piezoelectric sensing sheet body, the upper electrode and the lower electrode only have relative superposed parts in the effective resonance area, or when the effective working area and the ineffective area of the piezoelectric sensing sheet body are disconnected and are not connected, the upper electrode and the lower electrode also have relative parts in the ineffective area; the purpose of this is mainly to prevent leakage of transverse waves.
A first cavity 23 is arranged above the acoustic wave resonator units, the first cavity 23 surrounds a plurality of acoustic wave resonator units, and cap layers are arranged above and around the first cavity 23 to seal the first cavity 23. The cap layer comprises: a cap body 300 having a release hole with a predetermined diameter, and a capping layer 302 sealing the release hole 31. The cap layer body is of a single-layer film layer or a multi-layer film layer structure, and the material of each layer of film layer is selected from: silicon oxide, silicon nitride, silicon carbide, organic cured film. In this embodiment, the cap body 300 is a single layer film. Thickness range of the cap body 300: 5um to 50um, thickness range of the capping layer 302: 5um to 50 um. The thicknesses of the cap layer body 300 and the capping layer 302 can complement each other, the total thickness can be 10um to 100um, the adjustment is flexible according to the requirement of mold pressing resistance, and the mold pressing resistance of the cap layer of the scheme is obviously enhanced compared with that of a cap which only has an organic curing film under the same thickness.
The material of the capping layer 302 includes: inorganic dielectric materials, organic cured films. Such as: the material of the capping layer 302 may be silicon dioxide or silicon nitride, etc. commonly used in semiconductor processes, and the hole can be plugged at a faster deposition rate, the commonly used deposition rate is greater than 10 angstroms/second, a thin film starts to grow from the side wall of the release hole 31, and the plugging is finally realized by thickening the film layer around the release hole 31, so that the capping layer is embedded in the hole. The capping layer 302 may also be formed by adhering an organic curing film, which is relatively soft before curing and may be partially sucked into the holes under a vacuum condition to form an embedding effect. The formed capping layer 302 is partially embedded in the release hole 31, so that in the process of forming the capping layer 302, the material of the capping layer 302 does not enter the first cavity 23, which can significantly improve the performance of the filter, and in addition, the strength of the cap layer body 300 can be enhanced by partially embedding the capping layer 302 in the release hole 31.
The diameter of the release hole 31 is not necessarily too small, and is not necessarily too large. If the aperture is set to be too small, the efficiency of subsequent removal of the sacrificial layer is easily reduced; in the manufacturing process, the sacrificial layer is removed through the release hole 31 to form the first cavity 23, and then a capping layer 302 is formed to cover the cap body 300, the capping layer 302 seals the release hole 31, if the set aperture is too large, the capping layer 302 is easily filled into the first cavity 23 through the release hole 31, thereby affecting the performance of the resonator, or, in order to make the capping layer 302 only seal the release hole 31, the thickness of the capping layer 302 needs to be increased accordingly, thereby causing the volume of the resonator to be too large. For this reason, in the present embodiment, the aperture of the release holes is set to be 0.01um to 5um, and the density of the release holes above each first cavity 23 varies from 1 to 100 per 100 square micrometers. As an example, the cross-sectional shape of the release hole 31 is a circle, and the set aperture of the release hole 31 refers to the diameter of the release hole 31.
The distance from the top surface of the first cavity 23 to the top surface of the acoustic wave resonator unit is not preferably too small, nor too large. During the manufacturing process, if the distance is too small, the sacrificial layer in the first cavity 23 may easily cover the top surface of the acoustic wave resonator unit, the manufacturing process further includes forming a cap body 300 covering the sacrificial layer, and if the sacrificial layer may not cover the top surface of the acoustic wave resonator unit, the cap body 300 may be brought into contact with the top surface of the acoustic wave resonator unit, so as to affect the formation of the first cavity 23, and further adversely affect the performance of the resonator; if the distance is too large, the volume of the resonator is increased accordingly, thereby making it difficult for the manufacturing process of the resonator to meet the progress of miniaturization of the device, and the process time required for forming the sacrificial layer and removing the sacrificial layer is increased accordingly, thereby causing waste of process cost and time. For this reason, in the present embodiment, the distance from the top surface of the first cavity 23 to the top surface of the acoustic wave resonator unit is 0.3 to 10 micrometers.
In the manufacturing process, the longitudinal size of the subsequent first cavity 23 can be controlled by controlling the thickness of the sacrificial layer, so that the process difficulty of forming the first cavity is simplified, and the process flexibility is high. Moreover, since the sacrificial layer is formed by a semiconductor process, it is advantageous to improve the dimensional accuracy of the sacrificial layer, and accordingly, the dimensional accuracy of the first cavity is improved.
The cap layer of the thin-film piezoelectric acoustic wave filter surrounds at least two acoustic wave resonator units, the first cavity has a relatively large volume, and etching liquid or gas is easy to fill the first cavity, so that the release of a sacrificial layer in the manufacturing process is facilitated, the process compatibility is improved, and the process difficulty is reduced; the plurality of acoustic wave resonators share one cap layer, the release holes can be shared, and the flexibility of position selection of the release holes is increased. The acoustic wave resonator units as a whole can be better connected in series or in parallel.
In this embodiment, the SMR bulk acoustic wave filter, the acoustic resonator is a solid-state resonator, and the vacuum degree of the first cavity 23 is less than 10torr, for example, 1mtorr to 10torr, which is advantageous in that: when the sound wave is transmitted to the interface between the upper electrode and the first cavity with high vacuum degree, the sound wave can be subjected to better total reflection, and the better performance of the resonator and the filter is facilitated. And isolation portions 40 are provided between the sub caps 301 of the adjacent acoustic wave resonator units.
In this embodiment, between adjacent bulk acoustic wave resonator units, an upper electrode or a lower electrode of one of the bulk acoustic wave resonator units is electrically connected to the upper electrode or the lower electrode of the other bulk acoustic wave resonator unit. Fig. 1 shows two adjacent bulk acoustic wave resonator units, and an electrode interconnection sheet 24 is disposed between the adjacent bulk acoustic wave resonator units, and in this embodiment, the electrode interconnection sheet 24 connects the upper electrode 22 of one bulk acoustic wave resonator unit with the lower electrode 20 of another bulk acoustic wave resonator unit. The electrode interconnect wafer 24, the upper electrode 22, and the lower electrode 20 are all conductive materials, including: molybdenum, aluminum, tungsten, titanium, copper, nickel, cobalt, thallium, gold, silver, platinum or alloys thereof, and the materials of the three may be the same or different. In other embodiments, the two upper electrodes of two adjacent acoustic wave resonator units, or the two lower electrodes are connected through the electrode interconnection sheet. It should be understood that when the electrode interconnection sheet connects the upper and lower electrodes of the two acoustic wave resonating units, respectively, the two acoustic wave resonating units are connected in series, and when the electrode interconnection sheet connects the two upper electrodes or the two lower electrodes simultaneously, the two acoustic wave resonating units are connected in parallel. The electrode interconnect sheet may be integral with the upper electrode or the lower electrode, i.e., both are formed by patterning the same conductive layer.
In this embodiment, the filter further includes an electrical connection structure electrically connected to the upper electrode and the lower electrode of the resonator, respectively. For making electrical connection to external circuitry. The electrical connection structure includes: the conductive plug penetrates through the cap layer body 300 and the cap sealing layer 302 and is connected with the upper electrode 22 or the lower electrode 20; and the solder ball is positioned on the surface of the conductive plug.
The material of the conductive plug can comprise one or more of copper, aluminum, nickel, gold, silver and titanium, and the material of the solder ball can be tin solder, silver solder or gold-tin alloy solder. In this embodiment, the conductive plug is made of copper, and the solder ball is made of tin solder. The piezoelectric induction sheet body 21 is made of the following materials: at least one of aluminum nitride, zinc oxide, quartz, lithium niobate, lithium carbonate and lead zirconate titanate.
It should be noted that, in this embodiment, one filter includes two acoustic wave resonator units, and the two acoustic wave resonator units are located in one first cavity. In another embodiment, a filter may also include a plurality of acoustic wave resonator units, and the plurality of acoustic wave resonator units may be located in one first cavity or in a plurality of first cavities (each first cavity includes at least two acoustic wave resonator units). In addition, the structures of the multiple acoustic wave resonator units in one first cavity may be the same or different, for example, the sizes of two acoustic wave resonator units may be the same or different, and the heights of each resonator unit from the top surface of the first cavity may be the same or different. In order to realize different filter functions, a technician can set the number of the acoustic wave resonator units required by the filter and the combination mode of the acoustic wave resonator units and the first cavity according to requirements. The filter comprises at least two first cavities, so that the volume of the cavities is not too large, the requirement on the supporting strength of the cap layer can be balanced, the increase of the height of the cavities and the thickness of the cap layer is relieved, and the volume of the filter can be better controlled.
Example 2
The present embodiment provides a method for manufacturing a thin film piezoelectric acoustic wave filter, including:
s01: providing a first substrate;
s02: forming a plurality of acoustic wave resonator units on the first substrate, each acoustic wave resonator unit including a piezoelectric sensing sheet body, a first electrode and a second electrode which are used for applying a voltage to the piezoelectric sensing sheet body and are opposite to each other;
s03: forming a sacrificial layer on at least two acoustic wave resonator units and a spacing region between the acoustic wave resonator units;
s04: forming a cap layer body, covering the sacrificial layer, forming a release hole with a set aperture on the cap layer body, and removing the sacrificial layer through the release hole to form a first cavity;
s05: and forming a cover layer on the cover cap body, and partially embedding the cover layer into part of the release holes so as to seal the release holes.
It should be noted that S0N does not represent the sequence of steps.
Fig. 2 to 8 are schematic structural diagrams corresponding to different steps of a manufacturing method of a thin film piezoelectric acoustic wave filter according to an embodiment of the present invention, and the manufacturing method of the thin film piezoelectric acoustic wave filter will be described in detail with reference to fig. 2 to 8.
Referring to fig. 2, step S01 is executed: providing a first substrate;
the contents of the first substrate in embodiment 1 can be cited herein, and are not described herein again.
In this embodiment, the first substrate includes a first substrate 10 and a first dielectric layer 11 located on the first substrate 10, and a bragg acoustic wave reflection layer 12 is formed in the first dielectric layer 11 (in this embodiment, two acoustic wave resonance units are taken as an example in one cavity).
Referring to fig. 3, step S02 is performed: a plurality of acoustic wave resonator units are formed on the first substrate. The structure of the acoustic wave resonator unit is referred to in the relevant content of embodiment 1, and is not described in detail here. The figure schematically illustrates example 1.
In the method of forming the acoustic wave resonator unit in embodiment 1, a conductive film is formed on the first dielectric layer 11 by a physical vapor deposition method such as sputtering, and the conductive film is patterned to form the lower electrode 20; a piezoelectric film is formed on the lower electrode 20 and the first dielectric layer 11 by a vapor deposition process, the piezoelectric film is patterned to form a piezoelectric sensing sheet 21, and a conductive film is formed on the piezoelectric sensing sheet 21 and the lower electrode 20, the conductive film is patterned to form an upper electrode 22. In this embodiment, the method of forming the electrode interconnect wafer 24 includes: in forming the upper electrode 22 of one of the acoustic resonator elements, the conductive material forming the upper electrode directly forms the electrode interconnect 24, connecting the electrode interconnect 24 with the lower electrode of the other acoustic resonator element. The material of the electrode interconnection sheet 24 in this embodiment is the same as the material of the upper electrode. In other embodiments, the materials of the upper electrode, the lower electrode and the electrode interconnection sheet can be the same or different. But are all conductive materials such as: molybdenum, aluminum, tungsten, titanium, copper, nickel, cobalt, thallium, gold, silver, platinum or alloys thereof. The piezoelectric film is made of the following materials: at least one of aluminum nitride, zinc oxide, quartz, lithium niobate, lithium carbonate and lead zirconate titanate.
Referring to fig. 4, step S03 is performed: a sacrificial layer 50 is formed on the acoustic wave resonator unit and a spacing region between adjacent acoustic wave resonator units.
The sacrificial layer 50 is used to occupy a spatial position for the subsequent formation of a first cavity, that is to say, the first cavity is subsequently formed at the position of the sacrificial layer 50 by removing the sacrificial layer 50.
The material of the sacrificial layer 50 is a material that can be easily removed, and the subsequent process for removing the sacrificial layer 50 has little influence on the first substrate and the acoustic wave resonator unit, and in addition, the material of the sacrificial layer 50 can ensure that the sacrificial layer 50 has good coverage, thereby completely covering the acoustic wave resonator unit. For example, the material of the sacrificial layer 50 may include photoresist, polyimide (polyimide), amorphous carbon, or germanium.
In this embodiment, the material of the sacrificial layer 50 is amorphous carbon. The semiconductor device is formed through a semiconductor process (deposition process), and process compatibility and process reliability are high. Amorphous carbon can be removed by ashing in the later period, the process is simple, and the generated influence is small. When the material of the sacrificial layer is germanium, a deposition process may also be used to form the sacrificial material layer. In another embodiment, the material of the sacrificial layer 50 is photoresist or polyimide, and a coating process may be used to form the sacrificial material layer.
The thickness of the sacrificial layer is 0.3 to 10 microns. The reason for selecting this thickness is referred to the related description of the height of the first cavity, and is not repeated herein.
Referring to fig. 5to 7, step S04 is performed: forming a cap body 300 covering the sacrificial layer 50; a release hole 31 with a set aperture is formed on the cap body 300, and the sacrificial layer 50 is removed through the release hole 31 to form a first cavity 23.
The cap body 300 is made of a material that is easy to pattern, thereby reducing the difficulty of the subsequent process of forming the release holes. Moreover, the cap body 300 has a better step coverage capability, so that the degree of adhesion between the cap body 300 and the sacrificial layer 50, the first substrate or the inactive area of the acoustic wave resonator unit is improved, which is favorable for ensuring the shape quality and the size precision of the first cavity on the one hand, and the cap body 300 and the first substrate have higher bonding strength on the other hand, which is favorable for improving the reliability of the resonator on both sides. Forming the cap body comprises: forming one or more film layers by using a deposition process, wherein the material of each film layer comprises: silicon oxide, silicon nitride, silicon carbide or, forming one or more film layers by using a spin coating process or a film pasting process, wherein the material of each film layer comprises an organic curing film. The deposition process includes CVD and PVD, and the formation method is not described in detail. The cap layer body 300 has a thickness range of: 5um to 50 um.
In this embodiment, the material of the cap layer body 300 is a photosensitive cured material (one of organic cured films), and the cap layer body 300 can be patterned by a photolithography process, which is beneficial to reducing the process complexity and the process precision of the patterning process. Specifically, the photosensitive curing material is a dry film (dry film). The dry film is a permanent bonding film, and the bonding strength of the dry film is high, so that the bonding strength of the cap body 300 and the first substrate or the acoustic wave resonator unit is ensured, and meanwhile, the sealing performance of the first cavity is improved.
In this embodiment, the cap layer body 300 is formed by a film lamination (lamination) process. The annealing process is performed in a vacuum environment, and the step coverage capability of the cap layer body 300 is remarkably improved by selecting the annealing process, and meanwhile, the attaching degree of the cap layer body 300 to the sacrificial layer 50, the first substrate or the invalid region of the acoustic wave resonator unit is improved, and the bonding strength of the cap layer body 300 to the first substrate or the invalid region of the acoustic wave resonator unit is improved.
In other embodiments, the cap body may also be formed by using a liquid dry film, where the liquid dry film means that the components in the film-like dry film exist in a liquid state. Correspondingly, the step of forming the cap body comprises: coating a liquid dry film by a spin coating process; and curing the liquid dry film to form the cap layer body. Wherein, the cured liquid dry film is also a photosensitive material. In other embodiments, the material of the cap body may also be silicon oxide, silicon nitride, silicon carbide, or an organic cured film.
The release holes 31 are used to provide a process basis for the subsequent removal of the sacrificial layer 50.
The design of the release hole in the cap layer body needs to compromise the release effect of the sacrificial layer and the strength of the whole cap layer, the set aperture size range is between 0.1um and 3um, the density range is 1 to 100 in every 100 square microns and is unequal, so that the subsequent capping layer can be ensured to be well sealed to the release hole, the release efficiency of the sacrificial layer can be ensured, and when the capping layer is utilized to seal the release hole, the material of the capping layer can be ensured not to enter the first cavity to influence the performance of the acoustic wave resonator unit.
In this embodiment, the release holes 31 expose the top surface of the sacrificial layer 50. The top surface of the sacrificial layer 50 has a larger area than the sidewalls of the sacrificial layer 50, and thus, it is easy to set the lateral size and density of the release holes 31 according to process requirements.
In this embodiment, the material of the cap body 300 is a photosensitive cured material (a kind of organic cured film), and therefore, the cap body 300 is patterned by a photolithography process to form the release holes 31. By adopting the photolithography process, the process steps for forming the release hole 31 are simplified, and it is advantageous to improve the dimensional accuracy of the release hole 31.
In other embodiments, when the material of the cap layer body is a non-photosensitive cured material, a photoresist mask is formed by a photolithography process including coating, exposing, and developing, and the cap layer body is etched by a dry etching process through the photoresist mask to form the release hole. The dry etching process has anisotropic etching characteristics, is beneficial to improving the appearance quality and the size precision of the release holes, and can be a plasma dry etching process. Correspondingly, after the release hole is formed, the method further comprises the following steps: and removing the photoresist mask through a wet photoresist removing or ashing process.
Referring to fig. 8, step S05 is performed: forming a capping layer 302 on the cap layer body 300, and embedding a part of the capping layer 302 into a part of the release hole to seal the release hole 31.
In this embodiment, the process for forming the capping layer is performed in the process chamber with a vacuum degree of 1mtorr to 10torr, and when the capping layer 302 is formed by using the chemical vapor deposition process, the deposition rate is 10 angstroms/second to 150 angstroms/second, and the vacuum degree is 2 to 5 torr; when the physical vapor deposition process is adopted, the deposition rate is 10 angstroms/second to 20 angstroms/second, and the vacuum degree is 3 to 5 mtorr; when the capping layer 302 is formed by a film pasting process, the vacuum degree is 0.5torr to 0.8 torr. The material of the capping layer includes: inorganic dielectric materials, organic cured films; the organic cured film includes a dry film.
The encapsulation layer 302 is used for packaging the resonator, plays a role in sealing and moisture protection, and correspondingly reduces the influence of subsequent processes on the acoustic wave resonator unit, thereby improving the reliability of the formed resonator. Moreover, by sealing the first cavity 23, it is also advantageous to insulate the first cavity 23 from the external environment, thereby maintaining the stability of the acoustic performance of the acoustic wave resonator unit.
The capping layer 302 has better covering capability, so that the attaching degree and the bonding strength of the capping layer 302 and the capping layer body 200 are improved, and the reliability of the resonator is improved. In this embodiment, the material of the capping layer 302 is a photosensitive material (one of organic cured films), so that the capping layer 302 can be patterned by a photolithography process in the following step, which is beneficial to reducing the process complexity and the process precision of the patterning process. Specifically, the photosensitive material is a dry film. In other embodiments, the material of the capping layer may also be an inorganic dielectric material.
In this embodiment, the photosensitive material is a film-like dry film, and accordingly, the capping layer 302 is formed by a plating process, which significantly improves the adhesion and bonding strength of the capping layer 302 and the cap layer body 300. In other embodiments, the capping layer may also be formed by a deposition process or a coating process, depending on the material of the capping layer. For the detailed description of the capping layer, reference may be made to the related description of the cap body 300, and further description is omitted here.
In this embodiment, the bonding strength between the capping layer 302 and the cap layer body 300 is high, and under the combined action of the capping layer 302 and the cap layer body 300, the sealing performance of the first cavity 23 is improved, which correspondingly improves the reliability of the resonator.
The thickness scope of cap layer body is 5um to 50um, the thickness scope of capping layer is 5um to 50um, and the thickness of cap layer body and capping layer can each other be supplementary, and the gross thickness can be 10um to 100um, and in the alternative, the thickness of cap layer body 20um to 30um, the capping layer thickness is 5um to 15um, can realize well sealed effect again in order to guarantee structural strength. In the actual manufacturing process, the die pressing resistance is flexibly adjusted according to the die pressing resistance requirement, and the die pressing resistance of the cap layer is obviously enhanced compared with that of a cap which only has an organic curing film under the same thickness.
In this embodiment, through the sacrificial layer 50, the cap layer body 300 and the capping layer 302, the packaging of the resonator is realized by using a semiconductor process, and the process compatibility with the formation process of the acoustic wave resonator unit is high, which accordingly simplifies the process difficulty of forming the first cavity 23. Moreover, the sacrificial layer 50, the cap layer body 300, the capping layer 302 and the first cavity 23 are all formed through a semiconductor process, thereby improving the reliability of the resonator. The first cavity has a relatively large volume, so that the release of a sacrificial layer in the manufacturing process is facilitated, the process compatibility is improved, and the process difficulty is reduced; the plurality of acoustic wave resonators share one cap layer, so that the flexibility of position selection of the release hole is increased. The acoustic wave resonator units as a whole can be better connected in series or in parallel.
In this embodiment, forming the capping layer 302 further includes forming an electrical connection structure, in this embodiment, the electrical connection structure includes a conductive plug and a solder ball, and the method of forming the electrical connection structure includes: a via hole is formed through the cap body 300 and the capping layer 302, the via hole exposing the upper electrode or the lower electrode, and the method of forming the via hole includes dry etching. After the through hole is formed, the through hole is filled with a conductive material, the method for filling the conductive material comprises vapor deposition or electroplating, and the conductive material can comprise one or more of copper, aluminum, nickel, gold, silver and titanium. And forming a solder ball on the top surface of the conductive material by a ball mounting process after the conductive material is formed.
It should be noted that, in the present specification, all the embodiments are described in a related manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the structural embodiment, since it is substantially similar to the method embodiment, the description is relatively simple, and for the relevant points, reference may be made to the partial description of the method embodiment.
The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the appended claims.
Claims (13)
1. A thin film piezoelectric acoustic wave filter, comprising:
a first substrate;
a plurality of acoustic resonator units disposed on the first substrate, each of the acoustic resonator units including a piezoelectric sensing sheet, a first electrode and a second electrode facing each other for applying a voltage to the piezoelectric sensing sheet;
the cover cap layer is positioned on the first substrate and at least surrounds two acoustic wave resonator units so as to form a first cavity between the acoustic wave resonator units and the cover cap layer;
the cap layer comprises: the cap layer comprises a cap layer body and a sealing layer, wherein the cap layer body is provided with a release hole with a set hole diameter, the sealing layer seals the release hole, the cap layer body and the sealing layer are both made of dry films, the cap layer body and the sealing layer are both formed through a film pasting process, and the release hole is formed through a photoetching process; the set aperture of the release hole is 0.1 to 3 microns; the density of the release holes over the first cavity ranges from 1 to 100 of the release holes per 100 square microns;
and part of the capping layer is embedded into part of the release hole, the thickness of the cap layer body ranges from 5 micrometers to 50 micrometers, and the thickness of the capping layer ranges from 5 micrometers to 50 micrometers.
2. The thin film piezoelectric acoustic wave filter according to claim 1, wherein the plurality of acoustic resonator elements are distributed in at least two of the first cavities.
3. The thin film piezoelectric acoustic wave filter of claim 1, wherein a total thickness of the cap body and the capping layer is 10 μm to 100 μm.
4. The thin film piezoelectric acoustic wave filter of claim 1, wherein the cap body is a single film layer or a multi-film layer structure.
5. The thin-film piezoelectric acoustic wave filter according to claim 1, wherein the acoustic resonator element is a bulk acoustic wave resonator element, the first electrode is an upper electrode on the piezoelectric sensing plate, and the second electrode is a lower electrode under the piezoelectric sensing plate;
or,
the acoustic wave resonator unit is a surface acoustic wave resonator unit, and the first electrode and the second electrode are respectively a first interdigital transducer and a second interdigital transducer on the piezoelectric sensing sheet body.
6. The thin film piezoelectric acoustic wave filter according to claim 5, wherein an area where the upper electrode, the piezoelectric sensing piece, and the lower electrode of the bulk acoustic wave resonator unit overlap each other in a direction perpendicular to the first substrate surface is an effective resonance area, and the upper electrode and the lower electrode are stacked on each other only in the effective resonance area.
7. The thin film piezoelectric acoustic wave filter according to claim 1, wherein the acoustic wave resonator is a solid state fabricated resonator, and the degree of vacuum of the first cavity is 1mtorr to 10 torr.
8. The thin film piezoelectric acoustic wave filter according to claim 1, wherein the piezoelectric sensing sheet is made of a material including: at least one of aluminum nitride, zinc oxide, quartz, lithium niobate, lithium carbonate and lead zirconate titanate.
9. A method of manufacturing a thin film piezoelectric acoustic wave filter, comprising:
providing a first substrate;
forming a plurality of acoustic wave resonator units on the first substrate, each acoustic wave resonator unit including a piezoelectric sensing sheet body, a first electrode and a second electrode which are used for applying a voltage to the piezoelectric sensing sheet body and are opposite to each other;
forming a sacrificial layer on at least two acoustic wave resonator units and a spacing region between the two acoustic wave resonator units;
forming a cap layer body through a film pasting process to cover the sacrificial layer, wherein the cap layer body is made of a dry film;
forming a release hole with a set aperture on the cap layer body by adopting a photoetching process, wherein the set aperture of the release hole is 0.1-3 microns; removing the sacrificial layer through the release holes to form a first cavity, the release holes above the first cavity having a density in a range of 1 to 100 release holes per 100 square microns;
and forming a sealing layer on the cap layer body by a film pasting process, so that part of the sealing layer is embedded into part of the release holes to seal the release holes, wherein the sealing layer is made of a dry film, the thickness range of the cap layer body is 5-50 micrometers, and the thickness range of the sealing layer is 5-50 micrometers.
10. The method of manufacturing a thin film piezoelectric acoustic wave filter according to claim 9, wherein the process of forming the capping layer is performed in a process chamber having a degree of vacuum of 1mtorr to 10 torr.
11. The method of manufacturing a thin film piezoelectric acoustic wave filter according to claim 9,
when the sealing layer is formed by adopting a film pasting process, the vacuum degree is 0.5torr to 0.8 torr.
12. The method of manufacturing a thin film piezoelectric acoustic wave filter according to claim 9, wherein forming the cap body comprises:
one or more film layers are formed by a film pasting process.
13. The method of manufacturing a thin-film piezoelectric acoustic wave filter according to claim 9, wherein the acoustic resonator element is a bulk acoustic wave resonator element, the first electrode is an upper electrode on the piezoelectric sensing sheet, and the second electrode is an upper electrode under the piezoelectric sensing sheet;
or,
the acoustic wave resonator unit is a surface acoustic wave resonator unit, and the first electrode and the second electrode are respectively a first interdigital transducer and a second interdigital transducer on the piezoelectric sensing sheet body.
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