Bulk acoustic wave filter and electronic device

Abstract

The present disclosure provides a bulk acoustic wave filter and an electronic device. An example bulk acoustic wave filter is formed in and on a semiconductor substrate. The filter includes an air cavity embedded in the semiconductor substrate and at least one resonator formed in alignment with the air cavity, the resonator including an active layer sandwiched between a bottom electrode and a top electrode.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to French patent application number 2407822 entitled “Filtreàondes acoustiques devolume”, filed on July 17, 2024, which is incorporated herein by reference to the fullest extent permitted by law. Technical Field

[0003] This description generally relates to electronic devices, and more specifically to bulk acoustic wave (BAW) filters. Background Technology

[0004] Many electronic devices include at least one bulk acoustic wave filter. For example, such filters are integrated into mobile phones or smartphones to prevent interference from radio frequency signals emitted by other electronic devices or noise from external radio frequency sources that could disrupt the phone's radio frequency communication receiving channel.

[0005] Two types of bulk acoustic wave filters have been proposed: one is the so-called SMR (Solid-Mounted Resonator) filter, and the other is the so-called FBAR (Thin-Film Bulk Acoustic Resonator) filter, also known as a "membrane" bulk acoustic wave filter. An SMR filter typically consists of a membrane made of insulating material located on and in contact with a Bragg mirror, and a piezoelectric layer located on the membrane and sandwiched between bottom and top electrodes. The main difference between an FBAR filter and an SMR filter is that, in the case of an FBAR filter, the Bragg mirror is replaced by a gas cavity, above which the membrane is suspended. Providing a gas cavity gives the FBAR filter a higher efficiency than the SMR filter. In fact, the gas cavity provides a higher sound insulation effect than that achieved using a Bragg mirror with several double layers (approximately fifteen double layers would allow for a sound insulation effect comparable to that of a gas cavity, which is difficult to achieve in practice), thereby reducing energy loss.

[0006] However, existing acoustic filters, especially existing FBAR filters, suffer from numerous drawbacks. FBAR filters are particularly complex and costly to implement because current manufacturing methods require precise control over the flatness of the structure and the difficult step of forming the air cavity by removing the sacrificial layer. Furthermore, FBAR filters also suffer from overheating and mechanical strength issues. Therefore, existing FBAR filters are difficult to miniaturize. Summary of the Invention

[0007] There is a need to overcome some or all of the shortcomings of existing bulk acoustic wave filters (especially FBAR filters) and their manufacturing methods. It is particularly desirable to simplify the methods used to manufacture such filters and to achieve FBAR filters with higher mechanical strength and thermal performance than existing FBAR filters. This will allow for easier miniaturization of FBAR filters.

[0008] To this end, one embodiment provides a bulk acoustic wave filter formed in and on a semiconductor substrate, the filter comprising:

[0009] - An air cavity embedded in a semiconductor substrate; and

[0010] - At least one resonator formed inline with the air cavity, each resonator including an active layer sandwiched between bottom and top electrodes.

[0011] According to one embodiment, the filter includes a single resonator formed aligned with the air cavity.

[0012] According to one embodiment, the filter specifically includes a first resonator and a second resonator formed aligned with the air cavity.

[0013] According to one embodiment, the top electrodes of the first resonator and the second resonator have different thicknesses.

[0014] According to one embodiment, the bottom electrodes of the first resonator and the second resonator form a common electrode.

[0015] According to one embodiment, each top electrode is asymmetrical in shape when viewed from above.

[0016] According to one embodiment, the semiconductor substrate is made of silicon.

[0017] According to one embodiment, each resonator is separated from the air cavity by a portion of a semiconductor substrate with a thickness ranging from 300 nm to 1.5 μm.

[0018] One embodiment provides an electronic device, preferably a mobile phone or smartphone, which includes a radio frequency integrated circuit including at least one filter as described above.

[0019] One embodiment provides a method for manufacturing a bulk acoustic wave filter, the method comprising the following sequential steps:

[0020] a) Provide semiconductor substrates;

[0021] b) Forming a gas cavity embedded in the semiconductor substrate; and

[0022] c) Form at least one resonator aligned with the air cavity, each resonator including an active layer sandwiched between bottom and top electrodes.

[0023] According to one embodiment, the method further includes the step of forming a plurality of hollow vias in a semiconductor substrate between step a) and step b).

[0024] According to one embodiment, in step b), a gas cavity is formed by annealing the semiconductor substrate in a hydrogen atmosphere using a plurality of hollow through-holes. Attached Figure Description

[0025] The foregoing features and advantages, as well as other features and advantages, will be described in detail with reference to the accompanying drawings in the following description of specific embodiments given by way of illustration and not limitation, wherein:

[0026] Figure 1 This shows a side view, cross-sectional view, schematic diagram, and partial view of an example bulk acoustic filter;

[0027] Figure 2 This is a side view, cross-sectional view, schematic diagram, and partial view of an example bulk acoustic filter according to one embodiment;

[0028] Figure 3A , Figure 3B , Figure 3C , Figure 3D and Figure 3E The side view, cross-sectional view, schematic diagram and partial view illustrate a method for manufacturing according to one embodiment. Figure 2 The structure obtained at the end of the successive steps of the bulk acoustic wave filter method shown in the figure;

[0029] Figure 4 This illustrates a side view, cross-sectional view, schematic diagram, and partial view of an example bulk acoustic filter according to one embodiment; and

[0030] Figure 5 These are side views, cross-sectional views, schematic diagrams, and partial views of an example device for an integrated acoustic filter. Detailed Implementation

[0031] In the various figures, similar features are indicated by similar reference numerals. In particular, common structural and / or functional features in various embodiments may have the same reference numerals and may be provided with identical structures, dimensions, and material properties.

[0032] For clarity, only operations and elements useful for understanding the embodiments described herein are described in detail. In particular, the integration of bulk acoustic wave filters into various electronic devices that may implement such filters is not described in detail, and the described embodiments are compatible with all or most electronic devices that integrate at least one filter, which may be adapted to the capabilities of those skilled in the art upon reading this disclosure.

[0033] Unless otherwise indicated, when referring to two elements connected together, it means a direct connection without any intermediate elements other than the conductor, while when referring to two elements coupled together, it means that the two elements can be connected or they can be coupled via one or more other elements.

[0034] In the following disclosure, unless otherwise indicated, when referring to absolute position qualifiers (such as the terms "front", "back", "top", "bottom", "left", "right", etc.) or relative position qualifiers (such as the terms "above", "below", "higher", "lower", etc.) or orientation qualifiers (such as "horizontal", "vertical", etc.), the orientation shown in the figure shall be used.

[0035] Unless otherwise specified, the expressions “approximately,” “about,” “substantially,” and “around” indicate within 10% or 10°, and preferably within 5% or 5°.

[0036] Unless otherwise specified, in the following description, the qualifiers “insulating” and “conducting” mean electrical insulation and electrical conductivity, respectively.

[0037] Unless otherwise specified, the term “in contact with” means “in mechanical contact with”.

[0038] Figure 1 The images show a side view, cross-sectional view, schematic diagram, and partial view of an example bulk acoustic filter 100. For example, filter 100 is more specifically an "FBAR" (thin-film bulk acoustic resonator) type or a "membrane" bulk acoustic filter.

[0039] In the example shown, filter 100 includes a semiconductor substrate 101, such as a wafer or a piece of wafer made of a semiconductor substrate. As an example, semiconductor substrate 101 is made of silicon.

[0040] In the illustrated example, the filter 100 further includes an insulating layer 103 covering the top surface 101T of the semiconductor substrate 101. In the illustrated example, the insulating layer 103 is located within and in contact with the entire top surface 101T of the semiconductor substrate 101. For example, the insulating layer 103 has a thickness ranging from 1.3 to 4 μm. As an example, the insulating layer 103 is made of an oxide (such as silicon oxide). For example, the insulating layer 103 serves as a passivation layer for the top surface 101T of the semiconductor substrate 101.

[0041] In the illustrated example, the filter 100 also includes a cavity formed in the insulating layer 103. For example, the cavity 105 has a height strictly smaller than the thickness of the insulating layer 103, and a lateral dimension strictly smaller than the lateral dimension of the insulating layer 103. In this example, the walls of the cavity 105 are formed of the material of the insulating layer 103. For example, the cavity 105 has a height ranging from 0.3 to 2 μm. As an example, the cavity 105 is filled with air. In the illustrated example, the cavity 105 has substantially straight and substantially vertical sidewalls. In this example, the cavity 105 is substantially rectangular in cross-sectional view.

[0042] In the illustrated example, the filter 100 also includes an electrode 107 coated on a portion of the top surface of the insulating layer 103. In the illustrated example, the electrode 107 is located on and in contact with a portion of the top surface of the insulating layer 103. The electrode 107 is at least partially positioned aligned with the cavity 105. Figure 1 As shown in the example, electrode 107 is positioned, for example, mostly aligned with cavity 105. In this example, electrode 107 also includes a small portion extending laterally outward aligned with cavity 105. As an example, electrode 107 is made of a conductive material, such as a metal or metal alloy like aluminum.

[0043] In the illustrated example, the filter 100 also includes another insulating layer 109 coating the sides and top surface of the electrode 107. In this example, the insulating layer 109 also coats the portion of the top surface of the insulating layer 103 that is not coated by the electrode 107. In other words, the insulating layer 109 extends laterally outward, aligned with the electrode 107. For example, the insulating layer 109 is more specifically located on and in contact with the sides and top surface of the electrode 107 and the portion of the top surface of the insulating layer 103 that is not coated by the electrode 107. As an example, the insulating layer 109 is a piezoelectric layer, i.e., a layer made of a piezoelectric material, such as lithium niobate oxide (LNO), aluminum nitride, etc.

[0044] In the illustrated example, the filter 100 also includes another electrode 111 coated on a portion of the top surface of the insulating layer 109. In the illustrated example, electrode 111 is located on and in contact with a portion of the top surface of the insulating layer 109. For example, electrode 111 is at least partially positioned aligned with cavity 105. Figure 1 As shown in the example, electrode 111 is largely positioned aligned with cavity 105. In this example, electrode 111 has a lateral dimension that is significantly smaller than that of electrode 107. For example, electrodes 111 and 107 are the top and bottom electrodes of filter 100, respectively. As an example, electrode 111 is made of a conductive material, such as a metal or metal alloy like aluminum. For example, electrode 111 may be made of the same material as electrode 107.

[0045] For example, when viewed from above, electrode 111 has an asymmetrical shape.

[0046] In the illustrated example, filter 100 further includes another insulating layer 113 coating the sides and top surface of electrode 111. In this example, insulating layer 113 also coats the portion of the top surface of insulating layer 109 not coated by electrode 111. For example, more specifically, insulating layer 113 is located on and in contact with the sides and top surface of electrode 111, and also in contact with the portion of the top surface of insulating layer 109 not coated by electrode 111. For example, insulating layer 113 is made of oxide (e.g., silicon oxide). For example, insulating layer 113 is made of the same material as insulating layer 103. For example, insulating layer 113 serves as a passivation layer for the top surface of the structure (specifically electrode 111).

[0047] In the example shown, the filter 100 further includes contact pickup elements 115 for electrode 107 and contact pickup elements 117 for electrode 111. Figure 1 In the example shown, the contact pickup element 115 is located on and in contact with a portion of the top surface of the electrode 107 that is not aligned with or in contact with the cavity 105. When viewed in cross-section, the contact pickup element 115 has, for example, a T-shaped configuration, including a vertical portion extending from the top surface of the insulating layer 113 through the insulating layers 113 and 109 to the top surface of the electrode 107, and a horizontal portion extending laterally in contact with the top surface of the insulating layer 113 near the vertical portion of the contact pickup element 115.

[0048] Furthermore, in this example, contact pickup element 117 is located on and in contact with a portion of the top surface of electrode 111 aligned with and in contact with cavity 105. Viewed in cross-section, contact pickup element 117 has, for example, a T-shaped configuration, including a vertical portion extending from the top surface of insulating layer 113 through insulating layer 113 to the top surface of electrode 111, and a horizontal portion extending laterally on and in contact with the top surface of insulating layer 113 near the vertical portion of contact pickup element 117. Each contact pickup element 115, 117 is made of a conductive material, such as a metal or metal alloy. As an example, contact pickup elements 115, 117 are made of the same material.

[0049] Although not included in order to avoid overloading the attached diagrams Figure 1 As illustrated in the diagram, contact pickup elements 115, 117 are intended, for example, to couple or connect to one or more components or circuits outside of filter 100. As an example, contact pickup elements 115, 117 are intended to connect to the radio frequency communication circuitry of an electronic device.

[0050] In the illustrated example, filter 100 also includes an opening 119 positioned aligned with cavity 105. In this example, opening 119 extends from the top surface of insulating layer 113, through insulating layers 113 and 109, and through a portion of insulating layer 103 not coated with electrode 107, extending perpendicularly between the top surface of insulating layer 103 and the top surface of cavity 105. In the illustrated example, cavity 119 forms an opening in cavity 105. For example, opening 119 is formed as a via to allow the recovery of a sacrificial layer previously formed in insulating layer 103, thereby realizing cavity 105. The sacrificial layer is, for example, made of silicon.

[0051] In the example shown, filter 100 includes a membrane suspended above cavity 105, consisting of a portion of insulating layer 103 positioned aligned with electrode 111, and sandwiched between the top surface of cavity 105 and the top surface of insulating layer 103. For example, filter 100 includes an active region consisting of portions of insulating layer 103, electrode 107, insulating layer 109, and electrode 111 located above cavity 105 and aligned with electrode 111.

[0052] Electrodes 107 and 111, and a portion of the insulating layer 109 sandwiched between electrodes 107 and 111, are, for example, part of the resonator 121 of filter 100. For example, the insulating layer 109 is referred to as the active region of the resonator 121 of filter 100 because it is designed to be powered by a signal applied to electrodes 107 and 111 located on either side of this layer.

[0053] In operation, for example, a radio frequency (RF) signal is applied to electrodes 107 and 111 of filter 100 via contact pickup elements 115 and 117. This RF signal is, for example, an AC voltage. Applying the RF signal to electrodes 107 and 111 causes, for example, alternating expansion and contraction phases in insulating layer 109. This tends to cause resonator 121 of filter 100 to resonate and the membrane of filter 100 to vibrate. When the RF signal has a frequency substantially equal to the resonant frequency of the membrane of filter 100, the RF signal is not attenuated by filter 100, or attenuated very little. In contrast, when the RF signal has a frequency different from the resonant frequency of the membrane of filter 100, the RF signal is significantly attenuated by filter 100. For example, this allows for the avoidance of interference from RF signals emitted by other electronic devices or noise from external RF sources during the operation of the RF communication receiving channel.

[0054] A disadvantage of the bulk acoustic wave filter 100 is that its active region is separated from the semiconductor substrate 101 by the portion of the insulating layer 103 extending perpendicularly from the bottom surface of the electrode 107 to the top surface 101T of the semiconductor substrate 101 (in... Figure 1 As shown in the orientation, the portion of insulating layer 103 located on the left side of cavity 105 is separated. Insulating layer 103 is made of a material with a low thermal conductivity (typically lower than that of substrate 101), thus impairing the dissipation of heat generated by the active region of filter 100 when the membrane vibrates. This leads to unnecessary overheating of the active region of filter 100, which tends to degrade performance.

[0055] Another disadvantage of filter 100 is that it provides a cavity 105 and a through opening 119. As a result, filter 100 has relatively low mechanical strength. In addition, the materials of semiconductor substrate 101 and insulating layer 103 have different coefficients of thermal expansion, which also tends to weaken the structure due to temperature changes associated with the operation of filter 100.

[0056] Furthermore, a drawback of filter 100 stems from the fact that forming cavity 105 by removing the sacrificial layer constitutes a particularly difficult step to implement. In addition, the requirements for the flatness of insulating layers 103, 109, and 113, as well as electrodes 107 and 111, complicate the implementation of filter 100.

[0057] The aforementioned drawbacks limit the effectiveness of bulk acoustic filters (such as those mentioned in the previous reference). Figure 1 The use of the described filter 100) and the miniaturization of such filters are discussed.

[0058] refer to Figure 2 A detailed description of an embodiment that allows at least partial overcoming of these drawbacks.

[0059] Figure 2The diagram shows a side view, cross-sectional view, schematic diagram, and partial view of an example bulk acoustic wave filter 200 according to one embodiment. For example, the filter 200 is more specifically an FBAR filter.

[0060] Figure 2 The filter 200 shown includes... Figure 1 The common components of the filter 100 shown are not described in detail below.

[0061] Figure 2 The filter 200 shown is... Figure 1 The filter 100 shown differs in that it does not have a cavity 105 and an opening 119 formed in the insulating layer 103. According to one embodiment, the filter 200 includes an air cavity 201 embedded or covered in the semiconductor substrate 101. According to this embodiment, the cavity 201 is completely contained within the semiconductor substrate 101. Therefore, the cavity 201 is completely closed.

[0062] In the illustrated example, the cavity 201 is completely defined by the material of the semiconductor substrate 101. In this example, the cavity 201 is separated from the generally flat top surface 101T of the semiconductor substrate 101 by a portion of the semiconductor substrate 101. For example, the cavity 201 is located at a depth ranging from several hundred nanometers to several micrometers below the top surface 101T of the semiconductor substrate 101. In other words, the top surface of the cavity 201 is separated from the top surface of the semiconductor substrate 101 by a portion of the substrate 101 having a thickness ranging from several hundred nanometers to several micrometers. The thickness of the portion of the substrate 101 sandwiched between the top surface of the cavity 201 and the top surface 101T of the semiconductor substrate 101 ranges more specifically from, for example, 300 nm to 1.5 μm.

[0063] In the example shown, cavity 201 includes concave circular or curved sides (flanks). As an example, each side of cavity 201 has an arcuate shape when viewed in cross-section, for example, a semicircular shape.

[0064] When viewed from above, cavity 201 is, for example, rectangular in shape. However, this example is not limiting, and cavity 201 can more generally have any shape when viewed from above, such as polygonal shapes other than rectangles (e.g., squares, triangles, hexagons, etc.), or circular shapes (e.g., ovals, circles, etc.).

[0065] Electrode 107 is at least partially positioned aligned with cavity 201. For example, as Figure 2 As shown in the example, electrode 107 is primarily positioned aligned with cavity 201. In this example, electrode 107 also includes a small portion extending laterally outward aligned with cavity 201.

[0066] Furthermore, for example, electrode 111 is at least partially positioned aligned with cavity 201. For example, as Figure 2 As shown in the example, electrode 111 is positioned perfectly aligned with cavity 201. In this example, electrode 107 has a lateral dimension that is strictly smaller than the lateral dimension of electrode 107.

[0067] exist Figure 2 In the example shown, the contact pickup element 115 is located on and in contact with a portion of the top surface of the electrode 107 that is not aligned with the cavity 201. This allows for the avoidance or limitation of interference with the resonator 121 of the filter 200, compared to the case where the contact pickup element 115 contacts a portion of the top surface of the electrode 107 that is aligned with the cavity 201.

[0068] In the case of filter 200, the film of resonator 121 is formed by a portion of semiconductor substrate 101 sandwiched between cavity 201 and top surface 101T of substrate 101 and positioned to align with electrode 111.

[0069] Although Figure 2 Not shown, but the filter 200 may also include a protective cap for the resonator 121 of the filter 200 (e.g., a cap erected on the top surface 101T of the substrate 101), and the electrodes 107 and 111 of the filter 200 and the insulating layers 109 and 113 are located within the protective cap. Implementing such a protective cap according to the instructions of this disclosure is within the capabilities of those skilled in the art.

[0070] Assuming that filter 200, unlike filter 100, does not have a cavity 105 located within the insulating layer 103, then the insulating layer 103 of filter 200, for example, has a thickness much smaller than that of the insulating layer 103 in filter 100. As an example, in the case of filter 200, the insulating layer 103 has a thickness ranging from 0.5 to 1.5 μm, for example, equal to 0.8 μm. Compared to filter 100, this advantageously allows for improved heat dissipation of the resonator 121 in filter 200. The fact that the sides of the cavity 201 are circular further promotes heat dissipation.

[0071] Another advantage of filter 200 comes from the fact that cavity 201 is located within semiconductor substrate 101. This provides filter 200 with higher mechanical strength than filter 100. The fact that filter 200 does not have opening 1119 compared to filter 100 further contributes to the improved mechanical strength.

[0072] Figure 3A , Figure 3B , Figure 3C , Figure 3D and Figure 3EThe side view, cross-sectional view, schematic diagram and partial view illustrate a method for manufacturing according to one embodiment. Figure 2 The structure obtained at the end of the successive steps of the method for the bulk acoustic wave filter 200 shown.

[0073] Figure 3A The diagram illustrates the structure obtained at the end of the step of forming a plurality of hollow vias 301 in the semiconductor substrate 101.

[0074] In the example shown, the hollow via 301 extends from the top surface 101T of the semiconductor substrate 101 to a depth less than the thickness of the substrate 101. In other words, the hollow via 301 is a blind via and does not open on the bottom side of the semiconductor substrate 101.

[0075] When viewed from above, each hollow through-hole 301 has a cross-section of, for example, a generally square shape. However, this example is not limiting; when viewed from above, each through-hole 301 can generally have any shape, such as a polygonal shape other than a square (e.g., a rectangle, triangle, hexagon, etc.), or a circular shape (e.g., an ellipse, a circle, etc.). As an example, within manufacturing variations, the hollow through-holes 301 have substantially identical shapes and dimensions. For example, within manufacturing variations, the hollow through-holes 301 specifically have the same depth.

[0076] For example, the hollow through holes 301 are arranged in an array of rows and columns. For example, the rows are substantially perpendicular to the columns. For example, the array formed by the hollow through holes 301 has a substantially fixed pitch within manufacturing tolerances, that is, a substantially fixed center-to-center distance between two adjacent through holes.

[0077] For example, the hollow via 301 is achieved through a photolithography and then etching process. For this purpose, a photosensitive resin layer 303 is deposited on one side of the top surface 101T of the semiconductor substrate 101, for example. Alternatively, the photosensitive resin layer 303 may coat the entire top surface of the semiconductor substrate 101. In the illustrated example, the photosensitive resin layer 303 is more specifically located on and in contact with the top surface 101T of the semiconductor substrate 101.

[0078] For example, a through opening is then formed at the desired location of the future hollow through-hole 301 in the photosensitive resin layer 303, for example by isolating the photosensitive resin layer 303 via a mask and removing the isolated portion of the layer 303 in the case of positive resin, or removing the non-isolated portion of the layer 303 in the case of negative resin.

[0079] Once an opening is formed at the desired location of the future hollow via 301 in the photosensitive resin layer, the opening is extended in the semiconductor substrate 101, for example, by etching, such as by reactive ion etching (RIE) (e.g., deep reactive ion etching (DRIE)).

[0080] Figure 3B The diagram illustrates the structure obtained at the end of the further step of removing the photosensitive resin layer 303.

[0081] exist Figure 3B In the example shown, the photosensitive resin layer 303 was completely removed.

[0082] Figure 3C The diagram illustrates the structure obtained at the end of a further step of annealing the semiconductor substrate 101, where a hollow via 301 was previously formed.

[0083] In the example shown, annealing results in the formation of a cavity by the hollow via 301. Annealing is performed, for example, at a temperature of around 1000°C, in the range of 1000°C to 1150°C. For example, if the semiconductor substrate 101 is made of silicon, annealing is further performed in a hydrogen atmosphere. The fact that annealing is performed in hydrogen allows the silicon atoms of the semiconductor substrate 101 to have a higher surface mobility than in the absence of hydrogen.

[0084] During the annealing process, the silicon atoms in the semiconductor substrate 101 are rearranged, resulting in a structure with minimal surface roughness and surface energy without bulk loss. In practice, the bottom portion of the hollow via (i.e., near its bottom) tends to flare outwards, and the top portion (i.e., near the top portion 101T of the semiconductor substrate 101) tends to protrude outwards. Due to these phenomena, the hollow via 301 gradually transforms into a cavity 201, as... Figure 3C As shown in the diagram, the bottom of cavity 201 is located in semiconductor substrate 101 at a depth that is strictly smaller than the depth of the bottom of hollow via 301.

[0085] As an example, in order to achieve the above reference Figures 3A-3C The steps mentioned will be inspired by the description in the publication entitled “Empty-space-in-silicon technique for fabricating a silicon-on-nothing structure” by I. Mizushima et al., published in the November 2000 issue of the journal Applied Physics Letters.

[0086] Figure 3D The diagram illustrates the structure obtained at the end of a further step of depositing an insulating layer 103 on the top surface 101T side of a semiconductor substrate 101.

[0087] In the example shown, the insulating layer 103 coats the entire top surface 101T of the semiconductor substrate 101. More specifically, the insulating layer 103 is located on and in contact with the entire top surface 101T of the semiconductor substrate 101.

[0088] Figure 3E The diagram illustrates the structure obtained at the end of the further steps in realizing resonator 121.

[0089] During this step, an electrode 107, an active layer 109, and an electrode 111 are sequentially formed on surface 101T of the semiconductor substrate 101. For example, the electrode 107 is formed by depositing a conductive layer on the top surface of the insulating layer 103 and then patterning the conductive layer (e.g., by photolithography and then etching) so that only a portion of the conductive layer corresponding to the electrode 107 remains.

[0090] For example, insulation layer 109 is then deposited on the entire top surface of the structure.

[0091] For example, electrode 111 is then implemented in the same or similar manner as electrode 107, for example by depositing a conductive layer on the top surface of insulating layer 109 and patterning the conductive layer (e.g., by photolithography and then etching) such that only a portion of the conductive layer corresponding to electrode 111 remains.

[0092] Although not shown, insulating layer 113 is subsequently deposited, for example, on the entire top surface of the structure.

[0093] Then, contact pickup elements 115 and 117 are formed by openings in insulating layers 113 and 109 aligned with electrode 107 (for contact pickup element 115) and by openings in insulating layer 113 aligned with electrode 111 (for contact pickup element 117). For example, a conductive layer filling the openings is deposited on the entire top surface of the structure and patterned by, for example, photolithography followed by etching, so that only the portions of the conductive layer corresponding to contact pickup elements 115 and 117 are retained. As a variant, locally deposited conductive material can be provided. For example, filter 200 is thus obtained.

[0094] Figure 4 The diagram shows a side view, cross-sectional view, schematic diagram, and partial view of an example bulk acoustic filter 400 according to one embodiment. Figure 4 The filter 400 shown includes... Figure 2 The common components of the filter 200 shown below will not be described in detail further.

[0095] Figure 4 The filter 400 shown is... Figure 2 The filter 200 shown differs in that the filter 400 includes two resonators 421A and 421B located above and aligned with the cavity 201.

[0096] In the illustrated example, filter 400 includes an electrode 407 coated on a portion of the top surface of insulating layer 103. In the illustrated example, electrode 407 is located on and in contact with a portion of the top surface of insulating layer 103. Electrode 407 is at least partially positioned aligned with cavity 201. Figure 4 As shown in the example, electrode 407 is primarily positioned aligned with cavity 201. In this example, electrode 407 also includes a small portion extending laterally outward from cavity 201. For example, electrode 407 is similar to or identical to electrode 107 of filter 200. As an example, electrode 407 is made of a conductive material, such as a metal or metal alloy like aluminum.

[0097] For example, electrode 407 constitutes a bottom electrode shared by the two resonators 421A and 421B of filter 400. This allows for a simpler implementation of filter 400. However, this example is not limiting, and those skilled in the art can provide variations in which each resonator 421A, 421B of filter 400 includes a bottom electrode insulated from the bottom electrode of the other resonator 421B, 421A.

[0098] An active layer 109 coats the electrodes 407 of the filter 400. In the illustrated example, the active layer 109 is more specifically located on and in contact with the sidewalls and top wall of the electrode 109. Furthermore, in this example, the electrode 407 is shared by the two resonators 421A and 421B of the filter 400. This allows for a simpler implementation of the filter 400. However, this example is not limiting, and those skilled in the art can provide variations in which each resonator 421A, 421B of the filter 400 includes an active layer separate from the active layer of the other resonator 421B, 421A.

[0099] In the illustrated example, each resonator 421A, 421B of the filter 400 also includes another electrode 411A, 411B coated on a portion of the top surface of the active layer 109. In the illustrated example, each electrode 411A, 411B is located on and in contact with a portion of the top surface of the active layer 109. For example, electrodes 411A and 411B are at least partially positioned aligned with cavity 201. Figure 4 As shown in the example, each electrode 411A, 411B is positioned, for example, perfectly aligned with cavity 201. In this example, each electrode 411A and 411B has a lateral dimension that is strictly smaller than the lateral dimension of electrode 407. For example, electrodes 411A and 411B constitute the top electrode of filter 400. As an example, each electrode 411A, 411B is made of a conductive material, such as a metal or metal alloy like aluminum. For example, electrodes 411A and 411B are made of the same material as electrode 407.

[0100] For example, when viewed from above, each electrode 411A, 411B has an asymmetrical shape.

[0101] According to one embodiment, one of electrodes 411A and 411B has a thickness different from that of the other electrode 411B or 411A. In the example shown, electrode 411A (located in...) Figure 4 The left side (as shown) has a smaller electrode 411B (located in) Figure 4 The thickness shown is the thickness of the electrode 411A (oriented to the right). However, this example is not limiting, and those skilled in the art can provide variations that give electrode 411A a thickness that is significantly greater than that of electrode 411B.

[0102] In the example shown, the filter 400 further includes contact pickup elements 415 for electrode 407, contact pickup elements 417A for electrode 411A, and contact pickup elements 417B for electrode 411B. Figure 4 In the example shown, the contact pickup element 415 is located on and in contact with a portion of the top surface of the electrode 407 that is not aligned with the cavity 201. For example, when viewed in cross-section, the contact pickup element 415 has a similar T-shape, including a vertical portion extending from the top surface of the insulating layer 113 through the insulating layers 113 and 109 to the top surface of the electrode 407, and a horizontal portion extending laterally on and in contact with the top surface of the insulating layer 113 near the vertical portion of the contact pickup element 415.

[0103] Furthermore, in this example, contact pickup element 417A is located on and in contact with a portion of the top surface of electrode 411A positioned aligned with and in contact with cavity 201, and contact pickup element 417B is located on and in contact with a portion of the top surface of electrode 411B positioned aligned with and in contact with cavity 201. For example, contact pickup elements 417A and 417B have a similar T-shape when viewed in cross-section. The similar T-shape of 417A includes a vertical portion extending from the top surface of insulating layer 113 through insulating layer 113 to the top surface of electrode 411A, and a horizontal portion extending laterally in contact with the top surface of insulating layer 113 near the vertical portion of contact pickup element 417A; the similar T-shape of 417B includes a vertical portion extending from the top surface of insulating layer 113 through insulating layer 113 to the top surface of electrode 411B, and a horizontal portion extending laterally in contact with the top surface of insulating layer 113 near the vertical portion of contact pickup element 417B. Each contact pickup element 415, 417A, and 417B is made of a conductive material, such as a metal or alloy metal. As an example, contact pickup elements 417A and 417B are made of the same material as contact pickup element 415.

[0104] Although to avoid overloading the attached diagrams Figure 4 Not shown, but contact pickup elements 415, 417A, and 417B are intended, for example, to couple or connect to one or more components or circuits outside of filter 400. As an example, contact pickup elements 415, 417A, and 417B are intended to connect to the radio frequency communication circuitry of an electronic device.

[0105] The fact that electrodes 411A and 411B have different thicknesses allows resonators 421A and 421B to have different resonant frequencies. In this case, filter 400 is, for example, a bandpass filter, that allows signals having frequencies included within a frequency band substantially defined by the resonant frequencies of resonators 421A and 421B to pass through. As an example, the bandwidth of filter 400 is around gigahertz, for example, ranging from 0.5 GHz to 6 GHz.

[0106] Filter 400 has the same characteristics as the previous reference. Figure 2 Similar advantages are described for filter 200, particularly in terms of thermal performance and mechanical strength.

[0107] Figure 5 It is an integrated acoustic filter (e.g., previously referenced) Figure 4 Side view, cross-sectional view, schematic diagram, and partial view of an example device 500 (described as filter 400). In the example shown, device 500 is a mobile phone or smartphone.

[0108] In this example, device 500 includes processing circuitry 501 (AP), such as a microcontroller or main microprocessor of device 500. For example, processing circuitry 501 is connected to a radio frequency integrated circuit (RFIC) including at least one filter of type 200 or 400 (e.g., filter 400). Filter 400 is integrated, for example, in an electronic filter circuit. Figure 5 Not shown in detail. In the example shown, the RF integrated circuit 503 is connected to the antenna 505 (ANT), such as the RF communication antenna of device 500. Although, to avoid overloading the figures... Figure 5 Not shown in detail, but the RF integrated circuit 503 may also include components and circuits designed to perform functions such as impedance matching, amplification, modulation / demodulation, and switching.

[0109] Device 500 may also include other components, such as Figure 5 Other electronic components or circuits not described in detail herein. These components are in Figure 5 It is represented by function block 507 (FCT).

[0110] Although Figure 5The illustration shows a case where filter 400 is integrated in device 500, but this example is not limiting and those skilled in the art will be able to provide filter 400 in device 500 by replacing filter 400 with filter 200 or with a filter having a similar structure to filter 200 or 400 based on the indications of this disclosure.

[0111] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these embodiments can be combined, and other variations will be readily apparent to them. In particular, although... Figure 4 Consider, for example, the filter 400 comprising two resonators 421A and 421B located above cavity 201, but those skilled in the art will certainly be able to, based on the indications of this disclosure, Figure 4 The embodiments shown are adaptable to any number of resonators located above the same cavity implemented in a semiconductor substrate.

[0112] Based on the instructions of this disclosure, those skilled in the art will also be able to implement several filters in the same semiconductor substrate, for example by providing several embedded cavities formed in the same semiconductor substrate and at least one resonator positioned to align with each cavity.

[0113] In addition, although Figure 5 Consider the case of integrating filter 400 into a mobile phone or smartphone as an example, but the embodiments described are not limited to this example, but are more generally applicable to any device or system equipped with wireless communication capabilities, such as in the field of telematics. In particular, filter 400 or filter 200 can be integrated into motor vehicles to, for example, enable wireless internet access, communication between the vehicle and external equipment or systems, autonomous driving, etc., for end applications such as fleet management (the location, movement, status, and behavior of each vehicle) or real-time navigation systems, or to allow objects to communicate with vehicles (e.g., in the context of the Internet of Things (IoT)), so that nothing is interfered with by untrusted systems within a trusted communication "circle".

[0114] Finally, based on the functional descriptions provided above, the actual implementation of the embodiments and variations described herein is within the capabilities of those skilled in the art. In particular, when reading this disclosure, especially based on the references... Figures 3A-3E The described method for manufacturing filter 200, and the implementation of filter 400, are within the capabilities of those skilled in the art.

[0115] Furthermore, the described embodiments are not limited to the specific examples of materials and dimensions mentioned in this disclosure.

Claims

1. A bulk acoustic wave filter, formed in and on a semiconductor substrate, characterized in that, The filter includes: - An air cavity embedded in a semiconductor substrate; and - At least one resonator formed in alignment with the air cavity, each resonator including an active layer sandwiched between a bottom electrode and a top electrode.

2. The bulk acoustic wave filter as described in claim 1, characterized in that, This includes a single resonator formed by aligning with the air cavity.

3. The bulk acoustic wave filter as described in claim 1, characterized in that, Specifically, it includes a first resonator and a second resonator formed in alignment with the air cavity.

4. The bulk acoustic wave filter as described in claim 3, characterized in that, The top electrodes of the first resonator and the second resonator have different thicknesses.

5. The bulk acoustic wave filter as described in claim 3, characterized in that, The bottom electrodes of the first and second resonators form a common electrode.

6. The bulk acoustic wave filter as described in claim 1, characterized in that, in, When viewed from above, each top electrode is asymmetrical in shape.

7. The bulk acoustic wave filter as described in claim 1, characterized in that, The semiconductor substrate is made of silicon.

8. The bulk acoustic wave filter as described in claim 1, characterized in that, Each resonator is separated from the air cavity by a portion of a semiconductor substrate with a thickness ranging from 300 nm to 1.5 μm.

9. An electronic device comprising a radio frequency integrated circuit, characterized in that, The radio frequency integrated circuit includes at least one bulk acoustic wave filter as described in claim 1.

10. The electronic device as claimed in claim 9, characterized in that, The electronic devices are mobile phones or smartphones.

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