CN113114157A - Bulk acoustic wave filter and method of forming the same - Google Patents
Bulk acoustic wave filter and method of forming the same Download PDFInfo
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- CN113114157A CN113114157A CN202110412584.3A CN202110412584A CN113114157A CN 113114157 A CN113114157 A CN 113114157A CN 202110412584 A CN202110412584 A CN 202110412584A CN 113114157 A CN113114157 A CN 113114157A
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Classifications
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- H—ELECTRICITY
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H3/00—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators
- H03H3/007—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks
- H03H3/02—Apparatus or processes specially adapted for the manufacture of impedance networks, resonating circuits, resonators for the manufacture of electromechanical resonators or networks for the manufacture of piezoelectric or electrostrictive resonators or networks
Abstract
The invention provides a bulk acoustic wave filter and a forming method thereof. Through forming the supporting structure, the cavity is defined above the substrate, and the lower electrode and the film layer above the lower electrode are supported, so that the mechanical strength of the lower electrode and the film layer above the lower electrode above the cavity is improved, and the size of the release hole is increased to accelerate the release speed of the cavity space. And for the cavity above the substrate, the preparation method does not comprise a chemical mechanical polishing process, and the problem that the precision is difficult to control caused by the chemical mechanical polishing process is solved.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to a bulk acoustic wave filter and a forming method thereof.
Background
Semiconductor devices made using the inverse piezoelectric effect of piezoelectric materials are key elements of crystal oscillators and filters, which are often applied in Bulk Acoustic Wave (BAW) filters. Bulk acoustic wave filters are constructed mainly of the air gap type, which typically uses MEMS fabrication processes to form an air gap in a substrate for confining acoustic waves in a piezoelectric oscillator stack, and the solid-state fabricated (SMR) type. The structure has high Q value and good mechanical strength.
At present, the method for forming the air gap type filter can be seen with reference to fig. 1-3, which specifically includes the following steps.
First, referring to fig. 1, a substrate 10 is provided, and a cavity 10a is formed in the substrate 10. And depositing a sacrificial material on the substrate 10 and performing Chemical Mechanical Polishing (CMP) to fill the cavity 10a with the sacrificial layer 11.
In a second step, referring to fig. 2, a lower electrode 21, a piezoelectric layer 22 and an upper electrode 23 are sequentially formed on the substrate 10.
A third step, as shown in fig. 2 and 3, forming a release hole 22a at least penetrating the piezoelectric layer 22 to expose the sacrificial layer 11 in the cavity 110a, and removing the sacrificial layer through the release hole 22a to release the cavity 10 a.
In the forming method, the sacrificial layer 11 needs to be filled in the cavity 10a by using a chemical mechanical polishing process before preparing the electrode structure, however, the polishing precision of the chemical mechanical polishing process is difficult to control, and the problem of poor flatness of the substrate edge is often easily caused. In the above forming method, the end of the lower electrode overlapping the edge of the cavity 10a is used to support the lower electrode 21 and the film structure above the lower electrode, and the supporting strength is limited. On the one hand, the mechanical strength of the device is affected, and on the other hand, when the release holes 22a are prepared, the size of the release holes 22a needs to be controlled to be as small as possible, which directly results in slow release of the sacrificial layer 11, so that the time for soaking the sacrificial layer in the liquid medicine is long. In addition, in order to reduce parasitic effect and energy loss, the above forming method also needs to select a high-resistance silicon substrate, which further increases the cost.
Disclosure of Invention
The invention aims to provide a bulk acoustic wave filter and a forming method thereof, so as to optimize a preparation process and improve the mechanical strength of the prepared bulk acoustic wave filter.
In order to solve the above technical problem, the present invention provides a method for forming a bulk acoustic wave filter, including the following steps. Firstly, a substrate is provided, and a support structure is formed on the substrate, including: forming a dielectric layer on the substrate, and forming an annular groove in the dielectric layer, wherein the dielectric material surrounded by the annular groove forms a sacrificial part; and forming a support material layer on the dielectric layer, wherein the support material layer fills the annular groove to form a support column, the part of the support material layer covering the top surface of the dielectric layer forms a support layer, and the support layer transversely extends to the sacrificial part. Then, a lower electrode, a piezoelectric layer, and an upper electrode are sequentially formed on the support structure, the lower electrode is located directly above the sacrifice part, and at least an end portion of the lower electrode is mounted on the support layer, the piezoelectric layer covers at least the lower electrode, and the upper electrode is formed on the piezoelectric layer. Then, the sacrificial part is removed to form a cavity below the lower electrode.
Optionally, the support layer completely covers the top surface of the sacrificial part surrounded by the support posts, and the bottom surface of the lower electrode completely rides on the support layer.
Optionally, the support layer extends from outside the sacrificial part to the edge of the sacrificial part to form a bearing part, and the end part of the lower electrode is arranged on the bearing part of the support layer.
Optionally, the forming method of the support structure includes: after the support material layer is formed, removing the part of the support material layer above the sacrificial part, and reserving the part of the support material layer at the edge of the sacrificial part to form the bearing part. And when the lower electrode is formed, the lower electrode covers the exposed sacrificial layer, and the end part of the lower electrode is carried on the bearing part of the supporting layer.
Optionally, the projection of the lower electrode on the substrate is completely located within the projection range of the cavity on the substrate.
Optionally, the forming method of the support material layer includes: and executing a film deposition process, wherein the process temperature of the film deposition process is 300-1500 ℃.
Optionally, the method for removing the sacrificial part includes: a release hole is formed through the piezoelectric layer and the support layer to expose the sacrificial portion, and the sacrificial portion is removed through the release hole to release the cavity.
It is a further object of the present invention to provide a bulk acoustic wave filter comprising a substrate and a support structure, a lower electrode, a piezoelectric layer and an upper electrode formed on the substrate.
The supporting structure comprises a dielectric layer, supporting columns and a supporting layer, wherein the dielectric layer and the supporting columns are arranged on the substrate in the same layer, the supporting columns surround a cavity, the cavity and the dielectric layer are separated by the supporting columns, and the supporting layer is located on the dielectric layer and transversely extends to the upper portion of the cavity. And the lower electrode is positioned right above the cavity, and at least the end part of the lower electrode is carried on the support layer.
Optionally, the supporting layer covers the top opening of the cavity, and the bottom surface of the lower electrode completely rides on the supporting layer.
Optionally, the support layer laterally extends from outside the cavity to an edge position inside the cavity to form a bearing part, and an end of the lower electrode is mounted on the bearing part of the support layer.
Optionally, the projection of the lower electrode on the substrate is completely located within the projection range of the cavity on the substrate.
In the bulk acoustic wave filter and the forming method thereof provided by the invention, the support structure is formed above the substrate so as to at least support the lower electrode and the film layer above the lower electrode above the cavity. Namely, the supporting structure is utilized to support the lower electrode and the film layer above the lower electrode above the cavity, so that the supporting strength of the lower electrode and the film layer above the lower electrode is improved. Based on this, when the sacrificial part is removed to release the cavity space, the size of the release hole is increased, the removal speed of the sacrificial part is increased, and the soaking time of the whole substrate structure in the corrosive liquid is reduced. In addition, the cavity is defined above the substrate by the support structure, and the preparation process of the cavity above the substrate can be realized without using a chemical mechanical polishing process, so that the problem of difficult control of precision caused by the chemical mechanical polishing process is effectively avoided.
Drawings
Fig. 1 to 3 are schematic structural diagrams of a conventional method for forming a bulk acoustic wave filter during a manufacturing process thereof.
Fig. 4 is a schematic flow chart of a method for forming a bulk acoustic wave filter according to the present invention.
Fig. 5 to 9 are schematic structural diagrams of a method for forming a bulk acoustic wave filter in a first embodiment of the present invention during a manufacturing process thereof.
Fig. 10 to fig. 11 are schematic structural diagrams of a method for forming a bulk acoustic wave filter in a second embodiment of the present invention during a manufacturing process thereof.
Wherein the reference numbers are as follows:
10-a substrate;
10 a-a cavity;
11-a sacrificial portion;
21-a lower electrode;
22-a piezoelectric layer;
23-an upper electrode;
22 a-a release aperture;
100-a substrate;
210-a lower electrode;
220-a piezoelectric layer;
230-an upper electrode;
300-a support structure;
300 a-a cavity;
310-a dielectric layer;
310 a-a sacrificial portion;
310 b-an annular trench;
320-support column;
330-a support layer;
410-extraction electrodes;
420-contact pad.
Detailed Description
The core idea of the invention is to provide a bulk acoustic wave filter and a forming method thereof, wherein the cavity of the bulk acoustic wave filter is arranged above the substrate, so that the problem that the prior art needs to use a chemical mechanical polishing process with difficult control precision when the cavity is arranged in the substrate is solved, and the support strength of a film layer above the cavity is improved.
Specifically, the method for forming the bulk acoustic wave filter provided by the present invention can be referred to fig. 4, which includes the following steps.
In step S100, a substrate is provided.
Step S200, forming a support structure on the substrate, including: forming a dielectric layer on the substrate, and forming an annular groove in the dielectric layer, wherein the dielectric material surrounded by the annular groove forms a sacrificial part; and forming a support material layer on the dielectric layer, wherein the support material layer fills the annular groove to form a support column, the part of the support material layer covering the top surface of the dielectric layer forms a support layer, and the support layer transversely extends to the sacrificial part.
Step S300, sequentially forming a lower electrode, a piezoelectric layer, and an upper electrode on the support structure, where the lower electrode is located right above the sacrificial portion, at least an end portion of the lower electrode is mounted on the support layer, the piezoelectric layer at least covers the lower electrode, and the upper electrode is located on the piezoelectric layer.
Step S400, removing the sacrificial part to form a cavity below the lower electrode.
The bulk acoustic wave filter and the method for forming the bulk acoustic wave filter according to the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention. It will be understood that relative terms, such as "above," "below," "top," "bottom," "above," and "below," may be used in relation to various elements shown in the figures. These relative terms are intended to encompass different orientations of the elements in addition to the orientation depicted in the figures. For example, if the device were inverted relative to the view in the drawings, an element described as "above" another element, for example, would now be below that element.
< example one >
Fig. 5 to 9 are schematic structural diagrams of a method for forming a bulk acoustic wave filter in a first embodiment of the present invention during a manufacturing process thereof, and the method for forming the bulk acoustic wave filter in the first embodiment is described in detail below with reference to fig. 4 and fig. 5 to 9.
In step S100, as shown with particular reference to fig. 5, a substrate 100 is provided.
In the subsequent process, a cavity and an electrode stack are sequentially formed above the substrate 100, so that the cavity can be used to reduce the electrical parasitic effect between the substrate 100 and the electrode stack above. Therefore, the substrate 100 in this embodiment is not limited to a high resistance substrate, so that the substrate 100 is more flexible to select, which is beneficial to reduce the manufacturing cost of the device.
Of course, in other embodiments, the substrate 100 may still adopt a high-resistance substrate to improve the parasitic effect between the substrate 100 and the film layer thereon, and reduce the parasitic electrical loss. Specifically, the substrate 100 may be directly formed by a high resistance silicon substrate, and a resistance value of the silicon substrate is, for example, greater than 1500 Ω, and more specifically, 2000 Ω to 10000 Ω.
In step S200, and with particular reference to fig. 5 and 6, a support structure 300 is formed on the substrate 100. The support structure 300 serves to define a cavity region and to support a lower electrode, a piezoelectric layer, and an upper electrode, which are subsequently formed.
The forming method of the supporting structure 300 includes the following steps.
Step one, specifically referring to fig. 5, a dielectric layer 310 is formed on the substrate 100, and an annular trench 310b is formed in the dielectric layer 310, where the annular trench 310b surrounds the inner dielectric material to form a sacrificial portion 310 a. It is also contemplated that the annular groove 310b surrounds the cavity area.
Step two, referring to fig. 6 specifically, a support material layer is formed on the dielectric layer 310, the support material layer fills the annular trench 310b to form a support pillar 320, and a portion of the support material layer covering the top surface of the dielectric layer 310 forms a support layer 330. In this embodiment, the supporting layer 330 completely covers the top surface of the sacrificial portion 310a surrounded by the supporting posts 310.
The support material layer may be formed by a thin film deposition process, so as to improve the coverage of the support material layer on the dielectric layer 310 and ensure that the support material can fully fill the annular trench 310 b. In this embodiment, the thin film deposition process may be performed at a higher temperature to enhance the mechanical strength of the formed support material layer, thereby improving the support strength of the overlying film layer. Specifically, the process temperature of the film deposition process is 300-1500 ℃, and more specifically can be higher than 400 ℃.
Further, the material of the support material layer is different from that of the dielectric layer 310 (that is, the material of the support post 320 and the material of the support layer 330 are both different from that of the sacrificial portion 310 a), so that when the sacrificial portion 310a is subsequently removed, the support post 320 can be used to achieve better etching blocking, and the dielectric layer 310 outside the sacrificial portion 310a is prevented from being corroded. For example, the material of the support material layer includes polysilicon, silicon nitride, or the like; and, the material of the dielectric layer 310 includes silicon oxide or boron Phosphorus Silicate Glass (PSG), etc.
It should be noted that the top surface of the supporting structure 300 formed in this embodiment is a flat surface, which can provide a flat mesa for the subsequent preparation of the lower electrode, the piezoelectric layer and the upper electrode, thereby improving the quality of each film layer.
In step S300, referring specifically to fig. 7, a lower electrode 210, a piezoelectric layer 220, and an upper electrode 230 are sequentially formed on the support structure 300. Wherein the lower electrode 210 is located right above the sacrificial portion 310a, the piezoelectric layer 220 covers at least the lower electrode 210, and the upper electrode 230 is formed on the piezoelectric layer 220 and has a portion spatially overlapping with the lower electrode 210.
Specifically, at least an end portion of the lower electrode 210 is mounted on the support layer 330 extending to the sacrifice part. It is considered that the lower electrode 210 can be stably supported on the sacrificial portion 310a by the support layer 330 (the sacrificial portion 310a corresponds to a cavity formed in a subsequent process), so that most of the lower electrode 210 can be disposed directly above the sacrificial portion 310a, and an area of the lower electrode 210 laterally extending out of the sacrificial portion 310a is reduced (for example, an area ratio of the lower electrode 210 disposed directly above the sacrificial portion 310a is greater than or equal to 90%).
In this embodiment, the lower electrode 210 may be completely disposed right above the sacrificial portion 310a, and the bottom surface of the lower electrode 210 is completely mounted on the support layer 330. Further, the projections of the lower electrodes 210 on the substrate 100 are all located within the projection range of the sacrificial portion 310a on the substrate, i.e., the dimension of the lower electrodes 210 parallel to the substrate surface is smaller than the dimension of the sacrificial portion 310 a.
With continued reference to fig. 7, an extraction electrode 410 is also formed on the support structure 300, the extraction electrode 410 being disposed over the dielectric layer outside the sacrificial portion 310 a. The extraction electrode 410 is used for electrically connecting with the lower electrode 210 or electrically connecting with the upper electrode 230, so that the lower electrode 210 or the upper electrode 230 can be electrically extracted through the extraction electrode 410.
In this embodiment, the extraction electrode 410 and the lower electrode 210 may be formed simultaneously, and the preparation method thereof includes: first, an electrode material layer is formed on the substrate 100; next, the electrode material layer is patterned to form the extraction electrode 410 and the lower electrode 210, respectively. When the extraction electrode 410 is used for electrically extracting the lower electrode 210, the extraction electrode 410 and the lower electrode 210 can be connected with each other; alternatively, when the extraction electrode 410 is used to electrically extract the upper electrode layer 230, the extraction electrode 410 and the lower electrode 210 may be separated from each other.
As shown in fig. 7, the piezoelectric layer 220 covers the lower electrode 210 and the extraction electrode 410. That is, the piezoelectric layer 220 covers the sacrificial portion 310a and also covers the dielectric layer 310 outside the sacrificial portion. As described above, the top surface of the piezoelectric layer 220 formed in the present embodiment is relatively flat, which is beneficial to improving the quality of the piezoelectric layer 220. Wherein the material of the piezoelectric layer 220 comprises: at least one of zinc oxide (ZnO), aluminum nitride (AlN), and lead zirconate titanate (PZT).
And, the upper electrode 230 is formed on the piezoelectric layer 220. Wherein the upper electrode 230 and the lower electrode 210 may include the same material. For example, both include: the metal material includes, for example, one or a combination of molybdenum, gold, tungsten, platinum, ruthenium, titanium tungsten, aluminum, and titanium.
In a further embodiment, specifically referring to fig. 8, after forming the upper electrode 230, the method further includes: etching the piezoelectric layer 230 to further form a contact window in the piezoelectric layer 230, wherein the contact window exposes the extraction electrode 410; and forming a contact pad 420 in the contact window, wherein the contact pad 420 is electrically connected to the extraction electrode 410 and is used for electrically extracting the upper electrode 230 or the lower electrode 210.
It should be understood that the connection between the contact pad 420 and the upper electrode 230 or the lower electrode 210 is not explicitly illustrated in fig. 8, however, those skilled in the art will know that the connection between the contact pad 410 and the corresponding electrode can be accomplished according to the conventional known manner, and the detailed description thereof is omitted.
In step S400, referring specifically to fig. 9, the sacrificial portion 310a is removed to release the cavity 300a under the lower electrode 210.
Specifically, the method for removing the sacrifice part includes: a release hole (not shown) is formed through the piezoelectric layer 220 and the support layer 330 to expose the sacrificial portion 310a, and the sacrificial portion 310a is removed through the release hole to release the cavity 300 a.
It should be noted that, because the sacrificial portion 310a is surrounded by the supporting pillars 320 and spaced apart from the dielectric layer 310 on the periphery of the supporting pillars, when the sacrificial portion 310a is removed by etching, the dielectric layer 310 on the periphery can be prevented from being eroded under the barrier of the supporting pillars 320.
After the sacrificial part 310a is removed, the portion of the support layer 330 extending to the sacrificial part 310a is suspended on the cavity 300a, so that the support layer can be used for effectively supporting the film layer directly above the cavity 300a, and the mechanical strength of the film layer above the cavity 300a is improved. Based on this, when the release hole exposing the sacrificial portion 310a is formed, the size of the release hole can be increased to a certain extent, so as to accelerate the release speed of the sacrificial portion 310a and reduce the time for soaking the whole substrate structure in the etching solution.
< example two >
In the first embodiment, the support layer of the support structure completely covers the sacrificial portion, so that the support layer covers the top opening of the cavity after the sacrificial portion is removed, and the bottom surfaces of the lower electrodes are all mounted on the support layer.
In contrast to the first embodiment, in this embodiment, only the end of the supporting layer extends laterally onto the sacrificial portion, so that after the sacrificial portion is removed, only the end of the supporting layer extends to an edge position in the cavity, and the end of the lower electrode rides on the end of the supporting layer. The following describes the manufacturing method in this embodiment with reference to fig. 10 and fig. 11, where fig. 10-fig. 11 are schematic structural diagrams of the method for forming a bulk acoustic wave filter in the second embodiment of the present invention during the manufacturing process.
Referring first to fig. 10, in the process of manufacturing the support structure 300, after the forming of the support material layer, the method further includes: the part of the support material layer above the sacrifice part 310a is removed, and the part of the support material layer at the edge of the sacrifice part 310a is remained to constitute a load-bearing part. That is, the bearing portion of the support layer 330 is located on the edge of the sacrificial portion 310 a.
Next, as shown in fig. 10 and 11, when the lower electrode 210 is formed, the lower electrode 210 covers the exposed sacrificial layer 310a, and an end portion of the lower electrode 210 is mounted on the supporting portion of the supporting layer 330. That is, in this embodiment, the lower electrode 210 is carried by the carrier portion of the support layer 330 extending into the cavity 300a, so that the lower electrode 210 can be directly suspended above the cavity 300 a.
More specifically, the lower electrode 210 may be mounted on the supporting portion of the supporting layer 330 at the end portion of the entire circumference thereof. For example, if the cross-sectional shape of the lower electrode 210 parallel to the substrate surface is a polygon, a circle, or an ellipse, the edge of the polygon, the edge of the circle, or the edge of the ellipse of the lower electrode 210 are all mounted on the supporting portion of the supporting layer 330. And, an inner peripheral portion of the lower electrode 210 around the circumferential end thereof is disposed above the cavity 300a in a floating manner.
Similar to the embodiment, in the embodiment, the lower electrode 210 may be completely disposed in the area corresponding to the cavity 300 a. That is, the boundary of the lower electrode 210 does not exceed the boundary of the cavity 300 a.
In addition, after the lower electrode 210 is formed, the piezoelectric layer 220 and the upper electrode 230 are sequentially formed, and a specific forming method can refer to embodiment one and is not described herein again.
The structure of the prepared bulk acoustic wave filter will be described below based on the formation method described above. Reference is made in particular to fig. 9 and 11. The bulk acoustic wave filter includes a substrate 100, and a lower electrode 210, a piezoelectric layer 220, and an upper electrode 230 sequentially formed on the substrate 100.
Further, a support structure 300 is disposed on the substrate 100, and a cavity 300a is formed in the support structure 300 and is used for supporting the lower electrode 210, the piezoelectric layer 220 and the upper electrode 230.
Referring specifically to fig. 9 and 11, the support structure 300 includes a dielectric layer 310, support pillars 320, and a support layer 330, the dielectric layer 310 and the support pillars 320 are disposed on the substrate 100 in the same layer, the support pillars 320 surround a cavity 300a, the cavity 300a and the dielectric layer 310 are separated by the support pillars 320, and the support layer 330 is located on the dielectric layer 310 and also extends laterally above the cavity 300 a. It is believed that the support posts 320 serve to securely surround the cavity 300a and also assist in supporting the overhanging portion of the support layer 330 extending above the cavity.
Further, the lower electrode 210 is located right above the cavity 300a, and at least an end portion of the lower electrode 210 is mounted on the support layer 330 of the support structure 300 to support the lower electrode 210 with the support structure 300.
In an alternative, for example, referring to fig. 9, the supporting layer 330 covers the top opening of the cavity 300a, and the bottom surfaces of the lower electrodes 210 are all mounted on the supporting layer 330.
In another alternative, for example, referring to fig. 10, the carrying portion of the supporting layer 330 extends transversely to the edge position in the cavity 300a, and the end of the lower electrode 210 is carried on the carrying portion of the supporting layer 330.
That is, the support layer 330 of the support structure 300 can support the lower electrode 210 and the film layer thereon directly above the cavity 300a, thereby improving the mechanical strength and stability of the film layer above the cavity 300 a. Based on this, most of the lower electrode 210 can be disposed right above the cavity 300a, so as to reduce the area of the lower electrode 210 laterally extending out of the cavity 300a (which is equivalent to reducing the area of the lower electrode 210 laterally extending onto the dielectric layer 310). For example, the area ratio of the lower electrode 210 disposed directly above the cavity 300a is 90% or more. Since the cavity 300a has a lower dielectric constant relative to the dielectric layer 310, it is advantageous to reduce the parasitic effect between the lower electrode 210 and the substrate 100 by reducing the area of the lower electrode 210 on the dielectric layer 310.
In a specific embodiment, the lower electrode 210 may be completely disposed directly above the cavity 300a, and the projections of the lower electrode 210 on the substrate 100 are all located within the projection range of the cavity 300a on the substrate, that is, the size of the lower electrode 210 parallel to the substrate surface is smaller than the size of the cavity 300 a. Thus, the parasitic effect between the lower electrode 210 and the substrate 100 can be reduced as much as possible.
With continued reference to fig. 9 and 10, the piezoelectric layer 220 covers over the lower electrode 210 and also extends over the dielectric layer 310. And, the upper electrode 230 is formed on the piezoelectric layer 220, and the upper electrode 230 and the lower electrode 210 have a portion that spatially overlaps, i.e., the upper electrode 230 has a portion located directly above the cavity 300 a. Alternatively, the upper electrode 230 may be entirely formed right above the cavity 300 a; alternatively, the upper electrode 230 may extend laterally from the upper region of the cavity to the cavity region.
Wherein the upper electrode 230 and the lower electrode 210 may include the same material. For example, both include: one or a combination of molybdenum, gold, tungsten, platinum, ruthenium, titanium tungsten, aluminum, and titanium. And, the material of the piezoelectric layer 220 includes: at least one of zinc oxide (ZnO), aluminum nitride (AlN), and lead zirconate titanate (PZT).
Further, the dielectric constant of the dielectric layer 310 is lower than the dielectric constant of the piezoelectric layer 220. It is believed that the low dielectric constant dielectric layer 310 is spaced between the piezoelectric layer 220 and the substrate 100, which is beneficial for mitigating parasitic effects between the substrate 100 and the conductive film layer above the piezoelectric layer 220. For example, for the portion of the upper electrode 230 extending laterally above the dielectric layer 310, the piezoelectric layer 220 and the dielectric layer 310 are spaced between the upper electrode 230 and the substrate 100, so that the parasitic effect between the upper electrode 230 and the substrate 100 can be reduced.
In addition, in the present embodiment, the cavity 300a exists between the substrate 100 and the electrode layer, so that the electrical parasitic effect between the substrate 100 and the overlying electrode layer can be reduced by using the cavity 300 a. Therefore, the substrate 100 in this embodiment is not limited to a high resistance substrate, so that the substrate 100 is more flexible to select, which is beneficial to reduce the manufacturing cost of the device.
In summary, in the bulk acoustic wave filter and the method for forming the same, the supporting structure is used to define the cavity above the substrate. Compared with the prior art in which the cavity is arranged in the substrate, in the process of preparing the cavity above the substrate, the embodiment can avoid the problem that the precision is difficult to control due to the chemical mechanical polishing process without using the chemical mechanical polishing process. And the supporting structure is also used for supporting the lower electrode above the cavity and the film layer above the cavity, so that the mechanical strength of the lower electrode and the film layer above the lower electrode above the cavity is improved, on one hand, the device performance of the formed bulk acoustic wave filter is improved, and on the other hand, when the release holes are formed to release the space of the cavity, the size of the release holes can be further increased to accelerate the release speed of the cavity, and the soaking time of the whole substrate structure in the corrosive liquid is reduced.
It should be noted that, in the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other. Also, while the present invention has been described with reference to the preferred embodiments, the embodiments are not intended to be limiting. It will be apparent to those skilled in the art from this disclosure that many changes and modifications can be made, or equivalents modified, in the embodiments of the invention without departing from the scope of the invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the protection scope of the technical solution of the present invention, unless the content of the technical solution of the present invention is departed from.
It should be further understood that the terms "first," "second," "third," and the like in the description are used for distinguishing between various components, elements, steps, and the like, and are not intended to imply a logical or sequential relationship between various components, elements, steps, or the like, unless otherwise indicated or indicated.
It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention. It must be noted that, as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. For example, reference to "a step" or "an apparatus" means a reference to one or more steps or apparatuses and may include sub-steps as well as sub-apparatuses. All conjunctions used should be understood in the broadest sense. And, the word "or" should be understood to have the definition of a logical "or" rather than the definition of a logical "exclusive or" unless the context clearly dictates otherwise. Further, implementation of the methods and/or apparatus of embodiments of the present invention may include performing the selected task manually, automatically, or in combination.
Claims (11)
1. A method of forming a bulk acoustic wave filter, comprising:
providing a substrate;
forming a support structure on the substrate, comprising: forming a dielectric layer on the substrate, and forming an annular groove in the dielectric layer, wherein the dielectric material surrounded by the annular groove forms a sacrificial part; forming a support material layer on the dielectric layer, wherein the support material layer fills the annular grooves to form support columns, the part, covering the top surface of the dielectric layer, of the support material layer forms a support layer, and the support layer transversely extends to the sacrifice part;
sequentially forming a lower electrode, a piezoelectric layer and an upper electrode on the supporting structure, wherein the lower electrode is positioned right above the sacrificial part, at least the end part of the lower electrode is carried on the supporting layer, the piezoelectric layer at least covers the lower electrode, and the upper electrode is formed on the piezoelectric layer; and removing the sacrificial portion to form a cavity under the lower electrode.
2. The method of forming a bulk acoustic wave filter according to claim 1, wherein the support layer completely covers the top surface of the sacrifice part surrounded by the support posts, and the bottom surface of the lower electrode is completely carried on the support layer.
3. The method of forming a bulk acoustic wave filter according to claim 1, wherein the support layer extends from outside the sacrifice part to an edge of the sacrifice part to form a carrier part, and an end part of the lower electrode is carried on the carrier part of the support layer.
4. The method of forming a bulk acoustic wave filter according to claim 3, wherein the method of forming the support structure comprises: after the support material layer is formed, removing the part of the support material layer above the sacrificial part, and reserving the part of the support material layer at the edge of the sacrificial part to form the bearing part;
and when the lower electrode is formed, the lower electrode covers the exposed sacrificial layer, and the end part of the lower electrode is carried on the bearing part of the supporting layer.
5. The method of forming a bulk acoustic wave filter according to claim 1, wherein a projection of the lower electrode on the substrate is located entirely within a projection of the cavity on the substrate.
6. The method of forming a bulk acoustic wave filter according to claim 1, wherein the method of forming the support material layer comprises: and executing a film deposition process, wherein the process temperature of the film deposition process is 300-1500 ℃.
7. The method of forming a bulk acoustic wave filter according to claim 1, wherein the method of removing the sacrifice part includes: a release hole is formed through the piezoelectric layer and the support layer to expose the sacrificial portion, and the sacrificial portion is removed through the release hole to release the cavity.
8. A bulk acoustic wave filter, comprising:
a substrate;
the supporting structure comprises a dielectric layer, supporting columns and a supporting layer, wherein the dielectric layer and the supporting columns are arranged on the substrate in the same layer, the supporting columns surround a cavity, the cavity and the dielectric layer are separated by the supporting columns, and the supporting layer is positioned on the dielectric layer and also transversely extends to the upper part of the cavity;
a lower electrode located directly above the cavity, and at least an end portion of the lower electrode is mounted on the support layer;
a piezoelectric layer at least covering the lower electrode layer; and the number of the first and second groups,
and an upper electrode on the piezoelectric layer and having a portion spatially overlapping the lower electrode.
9. The bulk acoustic wave filter according to claim 8, wherein the support layer covers a top opening of the cavity, and a bottom surface of the lower electrode completely rides on the support layer.
10. The bulk acoustic wave filter according to claim 8, wherein the support layer extends laterally from outside the cavity to an edge position inside the cavity to constitute a carrier, and an end portion of the lower electrode is carried on the carrier of the support layer.
11. The bulk acoustic wave filter of claim 8, wherein a projection of the lower electrode on the substrate is located entirely within a projection of the cavity on the substrate.
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